Improvement of Sanitation and Solid Waste Management … · Improvement of Sanitation and Solid...

Division 44Environment and Infrastructure

Module 1: Technical Concepts

Improvement of Sanitation and Solid Waste Management in Urban Poor Settlements

Division 44Environment and Infrastructure

Module 1: Technical ConceptsImprovement of Sanitation and Solid Waste Management in Urban Poor Settlements

Eschborn 2005

Published by:

Deutsche Gesellschaft für

Technische Zusammenarbeit (GTZ) GmbH

Postfach 5180, 65726 Eschborn, Deutschland

Internet: http://www.gtz.de

Sectoral Project

“Improvement of Sanitation and Solid Waste Management in Urban Poor Settlements”

Division 44 - Environment and Infrastructure

OU 4412 - Water, Wastewater and Solid Waste Management

and Division 42 - Governance and Democracy

OU 4223 - Regional and Local Governance, Urban Development, Decentralisation

Responsible:

Sandra Spies und Klaus Weistroffer

Authors:

Dr. Heino Vest, Franziska Bosch

with Contributions from:

Harald Kraft, Frank Samol

Advisory Team:

Franziska Bosch, Martina Craemer-Moeller, GTZ, Elke Hüttner, GTZ

Hans-Joachim Hermann, GTZ, Prof. Peter Herrle, Alexander Jachnow

Prof. Burkhard von Rabenau, Frank Samol, Heike Santen, GTZ, Sandra Spies, GTZ

Klaus Weistroffer, GTZ, Dr. Heino Vest

Conceptualisation, Lay-out and Editing:

Frank Samol, B.U.S. – Büro für Umweltplanung und Stadtentwicklung

Translation from the German version published by GTZ in 2002 by:

Frank Samol, Ben Kern

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CONTENTS

0. INTRODUCTION 5Background and Context 6Objectives and Target Groups 10Contents Outline 11

1. TECHNICAL ASPECTS OF 13WASTE MANAGEMENT

2. SOLID WASTE MANAGEMENT 212.1 Challenges and Conceptual Approaches 222.2 Waste Generation 26

Tools and Instruments for Assessing Waste Generation

2.3 Waste Collection and Transport 28Drop-off Systems 28Pick-up Systems 32Unmotorised Systems 36Motorised Systems 38

2.4 Handling of Refuse and Its Further Treatment 40Sorting 40Composting 44Sorting and Recycling of Paper 48Sorting and Recycling of Plastics 52Sorting and Recycling of Metal 56Sorting and Recycling of Glass 58

2.5 Refuse Disposal and Depositing 60Small-scale Dumps and Landfills 60Disposal of Hazardous Waste 62

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3. WASTEWATER 653.1 Problems and Challenges 663.2 Wastewater Generation 70

3.3 Wastewater Discharging and Treatment Solutionsat Settlement Level (On-Site-Systems):72Latrines 72Dry and Compost Toilets- Separation of Urine 76Aqua Privies / Septic Tanks 80Biogas Plants 84Grease Traps 88Soakage Pits and Drainage Fields 90

3.4 Wastewater Disposal(Off-Site-Systems): 92Transport Containers and Vehicles 92Conventional and Unconventional Sewage Systems 94

3.5 Wastewater Treatment and Purification 98Decentralised Wastewater Treatment Plantsat Settlement Level 98Biological Treatment Plants 102

4. RAINWATER 1074.1 Problems and Challenges 1084.2 Drainage Systems 1104.3 Erosion Protection 1144.4 Rainwater Harvesting 118

ANNEX 123Solid Waste: Checklists, Tables, Design Criteria and References 124Wastewater: Checklists, Tables, Design Criteria and References 127Literature 135Illustration Credits 137

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INTRODUCTION0

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Today, worldwide urbanisation isthought of as an unstoppablecharacteristic of global societalchange. According to predictions, bythe year 2025 at least two thirds of theworld's population will live in cities.Most of this urban growth is takingplace in the developing world wheretwo billion people already live in cities- about twice as many as inindustrialised nations.

The dynamics of the urbanisationprocess, and especially its economic,social and spatial consequences, areamongst the greatest challenges ofour time. While cities offer anenormous and indispensable potentialfor the economic growth ofdeveloping countries in anincreasingly globalised economy, thenegative effects of urbanisation are

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INTRODUCTIONBACKGROUND AND CONTEXT

also alarmingly apparent, and theseinclude increasingly inadequatehousing and working conditions forthe poor and the ecological impact ofvirtually uncontrollable urban sprawl.

Failure of ConventionalUrban Planning andManagement Instruments

The emergence and expansion ofpoorly serviced illegal and informalsettlements in peripheral areas withinand outside urban agglomerations,have shown that conventional meansof city planning and management arenot able to cope with conditions ofaccelerated social change, highdemographic growth rates andincreasing urban poverty.

City planning, as a mechanism forcontrolling spatial development, is notfeasible in poor districts. In theseareas, land is traded illegally and builton without permission, and existingbuildings are often extended oraltered over long periods of time, withno official authorisation. To“formalise” these settlementscompletely would entail costs thatneither municipalities nor inhabitantscould handle. Restrictive policies(when applied) have done little ornothing to change the precariousliving conditions of the poor. At worst,they have inhibited rather thansupported legal, economic andinfrastructural improvement. Theneed for policies of decentralisationand the strengthening of local self-government have therefore beenvoiced with ever increasing intensityever since the 1996 United NationsConference on Human Settlements inIstanbul (Habitat II).

The Need for Flexibility andPro-active Solutions

City planning, as well as the manage-ment of housing and urban services,demand pro-active, financially feasiblestrategies adapted to real conditionsin order to take advantage of existingpotentials; they need to be replicable,to show immediate effects and besustainable. Although it is obviouslynot possible to equip informalsettlements with extensiveinfrastructures overnight, they can beupgraded gradually. This requiresprocedures that take into account thepotential for further futureimprovements.

Challenges of Urbanisation

Fast growing informal settlement /1/

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INTRODUCTION

New Partnerships betweenthe Public and the PrivateSector

The supposed dominance of publicsector agencies in the supply of socialand technical services, no longerholds true. Apart from partnershipswith the private sector, often the onlysensible alternative for achievingsustainable improvements depends onthe cooperation of various differentstakeholders, including the localpopulation and non-governmentalorganisations (NGOs).

For this reason, the significance of thediverse local stakeholders as well asthe variety of possible organisationaland financial structures should beseriously taken into account duringthe conception of urban managementprojects.

Problem: Precarious Living and Housing Conditions inUrban Poor Settlements

Poor settlements, in their variousforms, are especially vulnerable to thenegative impacts of urbanisation. Inmany cases, exclusion from legalprotection, urban services andinfrastructure leads to extremelyunhealthy living conditions resultingin high child mortality rates,widespread epidemic illness andchronic disease.

The Lack of WasteManagement Systems inPoor Settlements

The neglect of poor settlements bycity administrations is often justifiedby the fact that they are “informal”.The term is used to describe not onlytheir combination of uncertainlegalities, ownership rights and illegalconstruction activities, but also theireconomic structures, which yieldhardly any tax or revenues. Cityadministrations cite these factors toexplain their lack of input in socialand technical infrastructure.

Whatever the case, the consequence isthat in many African, Asian and LatinAmerican cities, barely a third of the

population is connected to municipalwaste management systems, while therest of the population relies on privatecontracts or self-help.

Importance of HousingRights as against WasteManagement

Infrastructure, waste management andsewerage systems are usually ofsecondary importance to theinhabitants during the initial phases ofinformal settlement. Securing a plotwith a right to stay there, andestablishing networks for incomegeneration are the primary concerns.Inward migration and continuousconstruction quickly lead to risingpopulation densities. This establishesand consolidates the social structureand built environment of a settlement,but also inevitably results in increasedrefuse and sewage managementproblems. In settlements withpopulation densities of more than2000 inhabitants per hectare,uncollected garbage, stagnant waterand lack of sanitary facilities can createserious health hazards, especially forwomen and children.

Settlement without security of tenure /2/

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INTRODUCTION

through private contractors, tocomplex neighborhood organisations.

However, these organisationalpossibilities only operate within thenarrow confines of each isolated localsituation, and this can produceproblems. For example, a drainagefacility that is not connected to themain sewage system may easilyintensify potential flooding in adjacentdistricts. Many issues related toinfrastructure and waste managementcan therefore only be resolved in asuitable and sustainable way, whenthey are coordinated in an overallsystem.

Decentralised Methods ofWaste Management

During the past twenty years, a varietyof methods for decentralised wastemanagement have emerged out ofpure necessity - and, in part, withoutexpensive subsidies. They havegenerally been characterised by theirability to adjust to specific social,

Potential: The Resourcefulness of the Urban Poor andtheir Commitment to Self-help

Despite the relatively unattractiveliving conditions they provide, poorsettlements, particularly in cities,continue to grow in size and density.The social and economic value at-tached to an urban location apparent-ly outweighs the numerous disadvan-tages. Moreover, people born andraised in an urban poor settlementfrequently have no other option.Today's generation of urban poor haslost its ties to the countryside andsurvives, physically and economically,within the boundaries of the city ordistrict.

Various Forms ofOrganisation

The majority of settlements, evenincluding temporary settlements,possess some sort of waste disposalmanagement. These range fromindividually arranged rubbishremovals, to area-wide servicing

Danger of Social andEconomic Disintegration

Neglect can lead to social andeconomic disintegration, which canresult in the area becomingmarginalised as the better-offinhabitants try to leave.

In addition, there is the problem ofdeficient technical infrastructure andservices, such as drainage or sewagedisposal systems, which cannot beeffectively tackled by public or self-help initiatives alone. Solutions oftenrequire intervention at many differentoperational levels and involvementacross various existing areas of activity.

Refuse as a source of income /3/

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INTRODUCTION

economic and cultural situations.Some were initiated within thecontext of international developmentco-operations; many innovativeapproaches were devised jointly byinhabitants and NGOs; and otherswere implemented through cityadministrations.

Alliance and Cooperation ofDifferent Stakeholders

What these approaches have incommon is that they not only pursuetechnical solutions, but they alsoincorporate organisational andfinancial aspects, and involve a varietyof local interest groups.

The improvement of technical andsocial infrastructure is of keyimportance in consolidated low-income settlements. Many such areasthat originated in the 1950's and1960's now have populations similarto those of a medium sized city, andyet their infrastructures remainsrudimentary. With steadily growingpopulations and increasing buildingdensities, health hazards haveincreased disproportionately andliving standards have plummeted.

The Importance ofImproving Technical andSocial Infrastructure for theConsolidation of Low-income Settlements

Nowadays, many of the urban poorhave access to potable water, althoughthey usually pay more for it thanmiddle-class citizens. Nonetheless,hygienic conditions in low-incomesettlements have become criticallyimportant to the quality of life of theirinhabitants. In the long run, anyadvantages of location will notoutweigh the lack of basic services inthese areas.

The standard of supply and disposalsystems tends to rank only third onthe priority lists of inhabitants, behindincome generation and security oftenure. Even so, the extent of under-serviced areas and the highproportion of the urban populationaffected have made the absence offunctional systems the number oneobstacle to overall development.

Integration of PoorSettlements into the UrbanFabric

Finding solutions for wastemanagement deficits in low-incomesettlements has become a mainelement in strategies aimed atimproving the general functionality ofcities and developing their economicpotential. The sustainable manage-ment of waste has acquired a signi-ficance that reaches far beyond itstechnical or sanitary dimensions. Itencompasses fiscal aspects as well asthe reorganisation of the relationshipbetween a city's administration and itspeople. What is required are, on theone hand, new forms of managingincreasingly heterogeneous urbanstructures in an economically sound,yet fair and balanced way, and on theother, the effective coordination ofthe very diverse stakeholders involvedin the development process.

Future Challenges: The Improvement of WasteManagement in Urban Poor Settlements

Housing conditions without adequatewaste management /4/

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INTRODUCTION

OBJECTIVES OF THIS PUBLICATION

• To appraise and document experience gathered in sectoral andcross-sectoral development cooperation projects

• To provide an overview of current international discussions onimproving waste management in urban poor settlements

• To offer orientation and support for the initiation, planning andimplementation of measures and activities for the improvementof waste management at the urban district or residential quarterlevels

• To present exemplary solutions and their institutional,organisational, and financial contexts

TARGET GROUPS

• People working onprojects dealing withhousing supply, citydevelopment, and refuseand waste watermanagement

• Interested laypersons andprofessionals from NGOs,local communityinitiatives and other grassroots organisations

• Professionals and decision-makers in communal andother responsibleinstitutions involved withwaste management inpoor areas.

Moreover, without the extensiveparticipation of affected inhabitants inthe planning, implementation, andmaintenance of systems, sustainabilitycannot be achieved. Seeminglymarginal themes, such as theorganisation of campaigns or thepricing of local services, are thereforealso dealt with in this publication in sofar as they relate to the main topic.

All volumes of this publicaton seriesfocus more on the content matter andoperational requirements of innovativeapproaches, and less on easilyreplicable formulas. The examplesgiven are intended to encourage thesearch for new solutions in specificsituations.

While the first volume presents thetopic of waste management in urbanpoor settlements in general, the sub-sequent three modules offer moreissue-specific recommendations for thedevelopment of local projectapproaches.

OBJECTIVES AND TARGET GROUPS

This publication intends to combinethe scattered theoretical and practicalknowledge acquired in the field ofdecentralised waste management, andmake it available for practical use indevelopment cooperation projects.The listings of waste managementprojects and the numerous individualproject profiles available on theinternet are not able to communicatethe innovative core, nor the basicparameters of novel approaches inways that enable comparisons andencourage their application in othercontexts. Moreover, the practicalexperience gained in individual GTZprojects has not, as yet, beensystematically brought together.

A treatment that deals only with thetechnical aspects of waste managementin low-income settlements, will nottackle the issues effectively. In order toachieve the sustainable improvementof people's lives, financial andorganisational factors must beconsidered as equally important.

The technical solutions described inthe present volume, Module 1, of thispublication series are intended as aguide and only provide basicbackground information on the mainissues to be considered in identifyingappropriate waste managementsolutions. The length of thisdocument is limited, and hencetechnical aspects have been describedas concisely as possible, and shouldnot be taken as a comprehensive basisfor detailed technical planning andimplementation.

For these purposes, it will there-fore be indispensable to draw onspecialised expertise and advisoryassistance.

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INTRODUCTION

Basic Concepts:

The introductory volume describes the basic information necessary for theconception, planning and implementation of measures to improve wastemanagement in urban poor settlements. Sample case studies and their concreteexperiences are used as references.

CONTENTS OUTLINE

Module 1:Technical Concepts

This first module documents proventechnical solutions and developscriteria for assessing their suitabilityfor use in different types of housingareas, and for dealing with differentconditions and problems.

Module 2:Participation, Self-help andPublic Relations

The second module is concerned withprocedures, instruments, andmethods for encouraging participationand self-help among inhabitants ofurban poor settlements during wastemanagement upgrading.

Module 3:Organisation of Operationsand Financing

The third module describes andevaluates possible approaches to theorganisation, maintenance andfinancing of waste managementsystems at the housing area level.

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INTRODUCTION

Module 1 Overview

The present volume deals with the following topics, and, where possible, these are illustrated by short summarised casestudies and examples of technical waste management solutions.

1. Technical Aspects of Waste ManagementThe introductory chapter of this module outlines the main framework conditions and the most important aspects that needto be considered in the design and implementation of technical solutions to waste management problems. It also gives anoverview of the basic information needed for selecting suitable technologies and approaches, and indicates appropriateselection criteria.

2. Solid WasteA first part of the second chapter describes the main problems, potentials and challenges of solid waste management inurban poor settlements and provides information on tools and instruments for assessing solid waste generation. The mostrelevant technical solutions and procedures for solid waste collection and transport, sorting and recycling, and final disposalare then presented and assessed in more detail.

3. WastewaterAs an introduction to wastewater management tasks and functions, the first section of this chapter outlines the mainproblems and challenges to be confronted in urban poor settlements, and describes basic concepts for assessing theamounts of wastewater to be disposed of and treated. More detailed descriptions and evaluations of technical options followin two main parts: on-site (i.e. settlement level) solutions for collecting and treating wastewater, and solutions forwastewater disposal and treatment both on-site and off-site.

4. RainwaterAs in chapters 2 and 3, an initial overview of the problems and challenges for rainwater management and erosion control inurban poor settlements is given. Against this background, the most relevant technical approaches and solutions for drainagesystems, erosion control measures and rainwater harvesting are presented and assessed.

AnnexThe annex comprises:• checklists, tables and design parameters for solid waste and wastewater management;• a list of literature that can provide more detailed information on the technical solutions and approaches presented;• photo and illustration credits.

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1 TECHNICAL ASPECTSOF WASTEMANAGEMENT

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Introduction

Depending on the specific contextand the resources available, varioustechnical solutions, procedures andforms of organisation can be used toprocess and dispose of solid waste(refuse), wastewater and rainwater inurban poor settlements. In general,the technologies involved are onlyone aspect in assessing whether aparticular waste management solutionis appropriate.

In most cases, social, cultural, financialor institutional aspects will be morerelevant than specific technicalmeasures, the choice of which areusually unproblematic. As a rule, thelong-term viability and sustainability ofwaste management projects andinitiatives depends more on factorssuch as social acceptance, thecapabilities of target groups and usersto operate and maintain equipmentand installations, the necessaryinstitutional and organisationalarrangements, and economicefficiency, in particular the

possibilities of cost recovery. Thus, the selection of appropriatetechnologies normally requires acareful assessment of the prevailingsocio-cultural, institutional, organi-sational and financial conditions, andthe possible scope of action will needto be based on these findings.

However, there may be situations inwhich the particularities of varioustechnical solutions of waste manage-ment tasks do become important. Insuch cases, it will not be sufficient toassess their advantages or disad-vantages primarily on the basis of thegeneral conditions. A comparison ofspecific technical aspects, such asefficiency, quality, ease of main-tenance, durability and environmentalimpact will then have to be used toselect the most favourable option.

A broad spectrum of appropriate andwell-tested technical solutions andprocedures for waste management inurban poor settlements has developed

over time, and an assessment of theapplicability of any of them requiresspecific technical know-how andpractical experience.

This chapter therefore, first outlinesthe basic information that will beneeded to select and plan appropriatetechnical waste managementsolutions, and how to collect andcompile this information. It thenpresents the most important technicalassessment criteria that will need tobe considered in selecting a particulartechnical solution in a specific context.

As far as is possible and useful, thepresentation also describes importantnon-technical aspects, or providesreferences to their detaileddescription in other modules of thispublication. Respective references areindicated by an arrow, thus:

u

The technical or technological aspect is only one of the factors inassessing whether a waste management solution is appropriate. Social, cultural, financial or institutional issues are often moreimportant than any specific technical solution.

The viability and sustainability of a technical waste managementsolution mainly depends on:

• its social and cultural acceptance;

• the capabilities of target groups and users to operate and maintaintechnologies and equipment;

• the institutional and organisational set-ups required;

• its economic efficiency and level of cost recovery.

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TECHNICAL ASPECTS OF WASTE MANAGEMENT

Densely built-up innercity areas needtechnical solutions different from thosefor peri-urban settlements /5/6/

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Since different urban quarters andsettlements may have considerablydifferent characteristics and problems,it will usually be necessary to analysethe prevailing development conditionsand problems carefully in order toidentify and develop wastemanagement measures that reflecteach settlement's particular situation.

Technical Aspects

The following technical aspects andinformation will be important inputsin analysing development conditions:• data on residential densities,

housing conditions and publicopen space;

• information on topography andgeology (terrain profiles, slopes,soil conditions);

• existing waste managementsolutions, and the quality andconditions of their respectivetechnical solutions:- method of collection and

disposal of household andcommercial refuse,

- condition of latrines, septictanks, sewage pipes andtreatment plants (as relevant),

- condition of possible opensewerage canals,

- type of rainwater and othersurface water drainage,

- risk of land slides andflooding.

• existing initiatives to improvewaste management;

• data on refuse and wastewaterproduced, on rainwater yield andon the corresponding needs fordisposal;

• possibilities of connecting toexisting municipal wastemanagement systems or networks;

• possibilities of recycling andmarketing solid waste components(compost, scrap metals, glass,paper, etc.).

u More detailed information on thekind of basic data needed for dif-ferent waste management taskscan be found in the correspond-ing chapters on refuse manage-ment, wastewater management,and rainwater drainage.

Social, Institutional andFinancial Aspects

The following social, institutional andfinancial information is indispensablefor the selection of appropriatesolutions:• problem perception and require-

ments of target groups and users;where relevant, considering socio-cultural or gender-specific factors;

• interests, willingness and possi-bilities of target groups and usersto participate in waste manage-ment activities (e.g. through self-help and mutual help, financialcontributions, payment of usercharges);

• existing community basedorganisations (CBOs) and non-governmental organisations(NGOs), which can be used asstarting points for waste manage-ment initiatives;

• interests, capacities andcapabilities of public sector(municipal or governmental)institutions responsible for wastemanagement services;

• existing fee and tariff systems forwaste managements services;possibilities of recovering servicecosts;

• possibilities of support fromgovernments or administrations,such as local governments,governmental sector institutions,etc..

u More detailed information on thekind of basic data needed forthese aspects can be found inModules 2 and 3, and in the firstvolume “Basic Concepts”.

Type of Information Needed to Select Appropriate Technologies and Procedures

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Criteria for Selecting Appropriate Technologies andProcesses

Participatory methods of informationcollection and problem analysis canfacilitate early target group and userinvolvement in the planning process.In particular, they can allow residentsand target groups to voice theirdemands, concerns and expectationswith regard to improved wastemanagement, and thus ensure thatplanned measures take these interestsinto account.

In addition to cooperation andinteraction with target groups andusers, special analyses or studies (e.g.on soil conditions, topographical andcadastral surveying, etc.) will usuallybe necessary to provide a sound basisfor decisions on possible technicalsolutions.

Because of the potentially wide rangeof activities and requirements that canbe derived from informationcollection and data analysis in theplanning phase, it will usually benecessary to prioritise measures forimproving hygienic conditions, anduse this as a basis for selectingappropriate technical solutions.

u Tools and instruments forparticipatory informationcollection and planning arepresented in more detail inModule 2 - “Participation andSelf-Help”.

Costs

Waste management in urban poor settlements will usually require low-cost orrelatively cheap solutions in order be affordable to target groups and publicsector service providers. Hence, one of the most important selection criteria willbe the costs involved in a particular technical solution.

In addition to net investment costs, the long-term costs of operations andmaintenance will be of particular importance:

Investment Costs

The investment costs of a particulartechnical solution depend on anumber of factors:• The level of technological

complexity: Considering theconditions in developingcountries, which are usuallycharacterised by low labour costsand high capital expenditure,sophisticated, automated andlabour saving equipment andprocesses will generally be lessappropriate than simple, labourintensive technologies.

• Physical factors, such as topo-graphy, geology, residentialdensity or accessibility (e.g.latrines need to be regularlyemptied and sludge transportedwhen the absorption capacity ofthe soil or space is limited).

• Possibilities for financing andcapital costs: financing of invest-ment costs by government sub-sidies or external donor grants isusually “cheaper” than loanfinancing.

A good indicator for comparing thecosts of different technical solutions isthe investment cost per household oruser.

Operating Costs

In previous practice, the importanceof the operational costs of technicalsolutions as a selection criterion hasoften been neglected. These aremainly determined by:• salaries and wages of operational

and administrative staff;• energy consumption and costs;• other necessary consumables

(lubricants, spare parts, cleaningagents, etc.);

• the expected life span ofequipment or system components,and the resulting depreciation;

• the needs for regular maintenanceand repair works.

u More detailed information on thistopic can be found in Module 3 -“Organisation and Finance”

Simple but efficient: Refuse containers/7/

Connection to municipal system:Sewerage /8/

Simple localised solution: Latrine/9/

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Efficiency and Quality

In addition to cost aspects, theefficiency and quality of technicalsolutions are other important criteriafor assessments.

The need for low-cost solutions andaffordability often calls for compro-mises and/or cuts in quality. Ingeneral, waste management measuresin urban poor settlements will provideless quality or convenience than thosein better-off, formal urban quarters.Nevertheless, even simple low-costsolutions can lead to significantimprovements. Important selectioncriteria for technical solutions are:• the amount of hygienic and

environmental improvement thatcan be achieved with the financialresources available;

• the possibilities of graduallyimproving and further developinginitially simple low-cost solutions.

Interfaces with Networks and Systems beyond SettlementLevel

Closely related to quality and efficiency, the necessities or possibilities forinterfacing with networks and systems outside the settlement or quarter arefurther important criteria in assessing waste management solutions. In this, adistinction should be made between:

• “Technical” interfaces that are theresult of the technical solutionselected, such as the connectionof local sewers to municipal orpublic sewerage networks or thecollection of refuse by municipalrefuse departments or enterprises.Such technical interfaces usuallyrequire close collaboration withthe responsible public or privateservices providers from the outsetof planning and preparation.Moreover, they usually mean thatat least part of services atsettlement level will later have tobe taken over by the public(municipal) or private sectoroperators who are responsible forwaste management operations atcity-wide level.

• “Systemic” (institutional)interfaces, resulting from thenecessity to coordinate projects orparticular measures with public ormunicipal institutions responsiblefor waste management services.For technical on-site solutions thatdo not need to connect to overallsystems (e.g. the construction oflatrines), coordination orcooperation with responsiblesector institutions may, in anycase, be necessary or useful, e.g.to obtain official approval of awaste management measure. Theneed for such coordination andcooperation should thus becarefully assessed, even when itseems not to be required by thetechnical option selected.

Complex technical solution with a higherneed for maintenance: Waste compactortruck in Aqaba, Jordan /11/

High organisational challenge:Operations of sludge pumping trucks

/12/

Simple technology: Manual push-carts forrefuse collection in Benin

/10/

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Ease of Operation and Use

The ease of operation and use of atechnical solution or process is mainlydetermined by two factors:• its level of complexity and the

skills needed to make it function;• the capabilities and skill levels of

users and target groups.

In the selection of technicalequipment, solutions or processes,the relationship between both factorsshould be adequately considered.For more complex solutions, or incases where user skills and capabilitiesare inadequate, complementarytraining and advisory assistance will beneeded. This should be considered inplanning and preparation.

Maintenance Requirementsand Durability

Maintenance requirements anddurability of materials, equipment andsystem components are furtherimportant assessment criteria.

Maintenance requirements and dura-bility largely depend on the complex-ity of a technology:• Simple technical solutions often

require less maintenance or havelonger maintenance intervals.Moreover, their maintenanceusually needs relatively less skilland technical know-how, and canthus be secured more easily; this,if necessary, can be supported bycomplementary training.

• More complex technical solutionsgenerally present a higher chall-enge for maintenance and repairwork. On the other hand, they areoften more efficient and canprovide a better service quality.

.

Requirements for Operationsand Organisation

Different technical solutionsgenerally call for differentoperational and organisational set-ups. Operational forms andorganisational structures also relateclosely to some of the aspectsdescribed above, including:• ease of operation and use;• maintenance requirements and

durability;• technical and systemic interfaces

with networks and institutionsbeyond settlement level;

• costs of operations,maintenance and assetdepreciation.

In most cases, the operational andorganisational challenges increasewith a technical solution's level ofcomplexity. However, even simpletechnical solutions require aminimum of stable organisational orinstitutional structures in order tobe sustainable.

u Module 3 - “Organisation andFinance”

Self-help in the construction of a sewernetwork /14/

Reasonable import of technology:Machine for paper pressing in Egypt /13/

Limited social acceptance: Refuse col-lection and recycling - the Zabaleen ofCairo

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Accessibility of TechnicalSolutions and Technologies

As a consequence of economicglobalisation, most up-to-datetechnologies for urban wastemanagement are available almosteverywhere (albeit at very differentcosts). Theoretically, they couldtherefore also be used in urban poorsettlements. However, due theirtechnical complexity, maintenancerequirements or costs, manytechnologies and related equipmentare only partially appropriate or evencompletely inappropriate in thiscontext.

On the other hand, importingtechnologies can make sense if ithelps achieve technically andinstitutionally sustainableimprovements at reasonable costs.Machines, equipment andtechnologies from countries withsimilar development levels thatcorrespond to specific local conditions(e.g. with regard to labour and capitalcosts or soil conditions) can beapplied. The needs and costs for spareparts, repairs and staff training will,however, have to be considered.

Social and CulturalAcceptance

Specific social, cultural, religious orethnic factors can have a considerableinfluence on a technical solution'slevel of acceptance and willingness tobe involved in self-help andparticipation. In many cultures, thehandling and collection of refuse isseen as a low status activity, which isoften designated to disadvantagedsocial groups, e.g. to Coptic Christiansin Islamic Egypt or to members ofspecial castes in Hindu countries. Thehandling of human excrement is oftensubject to similar taboos.

Specific socio-cultural conditionsshould thus be identified in theplanning and preparation of wastemanagement initiatives, and beadequately considered in the selectionof technical options. On the otherhand, existing prejudices againstspecific technical solutions can beovercome by information, awarenessraising campaigns and public relationsefforts.

u Module 2 - “Participation andSelf-Help”

Possibilities for Self-help

The possibilities for target group anduser self-help (e.g. in form of labouror other contributions in kind) arelargely determined by the ease ofoperations and use of a technicalsolution.

But even more complex technicalsolutions, such as the construction ofsewerage networks or retaining wallsagainst soil erosion or landslides, canat least partially be done through self-help (e.g. digging trenches or otherearthworks).

Basing an assessment of self-helppossibilities on technical aspects alonehowever, will usually be insufficient.Poor target groups often have to fightfor their livelihood on a daily basis,and this has to be taken intoconsideration. Thus the possibilitiesand scope for self-help can be limited.

u Module 2 - “Participation andSelf-Help”

Problems transferred “externally”: Dumping refuse at the urban fringe /16/

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Environmental Impacts andEnvironmental Balances

In the past, the environmental impactsand the environmental balances oftechnical solutions have often beenneglected in the assessment of wastemanagement solutions.

Although the overall objective of mostwaste management projects is toimprove hygienic and environmentalconditions for residents, problems areoften transferred elsewhere, that is,they are “externalised”. This isparticularly true where solutions atsettlement level are not fullyintegrated into functioning city-widewaste management systems, e.g.sewerage systems without final sewagetreatment facilities, or refusecollection without suitable landfills ordumping sites.

The selection of appropriate technicalsolutions should thus also considerthe following: • In cases of interfacing with or

connection to city-wide systems(off-site solutions): the existenceof sustainable solutions for wastedisposal outside the settlement, orthe possibilities of creating orintroducing environmentallysound final disposal options overtime.

• In cases of local solutions atsettlement level (on-sitesolutions): their impact withregard to soil contamination,vegetation, pollution of groundand surface water, and otheremissions.

Criteria for selecting technical waste management solutions for urbanpoor settlements:

• low investment and operational costs; saving of energy andother consumables

• efficiency: possibility of significant improvements even throughtechnically simple solutions

• appropriate consideration of technical and systemic interfaceswith city-wide networks and systems

• ease of use and operations corresponding to the skills andcapabilities of users and target groups

• low requirements for maintenance and repair; durability with along functional life span

• requirements for operational organisations that correspond tothe capacities of local stakeholders, organisations andinstitutions

• locally or regionally produced or purchased technologies

• adequate consideration of self-help potentials and possibilitiesof user and target group participation and/or contribution

• social acceptance

• positive environmental impacts and balances

21

SOLID WASTEMANAGEMENT2

22

2.1 SOLID WASTE MANAGEMENT

CHALLENGES AND CONCEPTUAL APPROACHES

Refuse is generally perceived asmaterial that the owner no longerneeds and wishes to dispose of. Thetraditional form of refuse disposal is tojust throw it away and/or have ittransported by a refuse collectionservice to a landfill or dumping site.

Today, this form of disposal (end-of-pipe technology) has not yetcompletely vanished, but has generallybecome less acceptable. Simple refusedisposal has developed into solidwaste management, a complex system,involving various measures andactivities which increasingly focuseson the reduction and recycling ofrefuse material. Environmentallysound, resource-conserving wastemanagement aims to recycle thelargest possible number of wastecomponents and reintroduce theminto the economic cycle in order toreduce the consumption of valuablematerial resources and energy.

Solid waste management, as applied inmost industrialised countries today,prioritises the reduction and recyclingof refuse over its final disposal.Environmental laws or otherregulations aim at only allowing finaldisposal after all possible means toreduce or recycle waste material havebeen made use of.

Basic Concepts of Solid Waste Management inIndustrialised Countries

Hierarchy of Solid WasteManagement

1. First priority: avoidanceand reduction of waste

• avoidance of waste inproduction processes

• use of products with alow waste constituentsor that generate lowamounts of waste

• reduction of hazardouswaste materials bysorting and separation

2. Second stage: wastereuse and recycling

• reuse of goods orproducts

• recycling of material

• composting of organicwaste

• energy recycling

3. Only then, final stage:end disposal

• sanitary landfill sites

• waste incineration

From refuse disposal tosolid waste management aspart of a recycling economy

This new understanding of solid wastemanagement has only slowly takenhold in developing countries.

In most of these countries, govern-ments, political bodies and institutionsresponsible for solid waste manage-ment still perceive waste as refuse tobe disposed of, rather than as aresource that supplies, among otherthings, reusable materials. Traditionalmethods of refuse disposal still largelyprevail, and, in most cases, theyfunction badly. Even in mega-cities,such as Cairo, Caracas or Manila, well-managed sanitary landfill sites are stillan exception, and refuse collectionand disposal are often erratic and ofbad quality. In parallel to formal refusecollection and disposal services, ahuge informal sector for refusecollection and recycling has developedin many cities which provides incomeand jobs for some of the poorpopulation.

More recent initiatives to privatise orlicense waste management in the formof concessions, which have emergedin many larger cities or metropolitanareas over the past 10-15 years, havehad little impact so far on the lowquality of waste management services.Part privatised waste managementservices, which largely remain publiclyorganised and regulated, still tend tobe only available to the formal parts ofcities and to rich or middle-incomeresidential areas.

Solid Waste Managementin Developing Countries

23



Solid Waste Management in Urban Poor Settlements

or walled transfer stations whereresidents can discharge their refuse.In the best case, containers or othercollection points are regularly emptiedby municipal refuse collectionservices; more frequently however,such services can be rather unreliable,and serious health hazards, as withinformal dumping sites, can arise fromthese intermediate collection points.

As for private refuse collectors, whooften collect and recycle refuse inwealthier formal residential areas, theyhave little interest in extending theirservices to poorer areas, whererecyclable waste materials are difficultto find.

Problems

In urban poor settlements, well-organised solid waste management israre. In most settlements, residentshave no alternative other than todispose of household and commercialrefuse in streets and alleys, in publicopen spaces, in valleys or creeks, or insewage or rainwater drainage canals.Informal dumping sites at the fringesof settlements are common, resultingin serious environmental hazards(from smouldering fires, the pollutionof surface water, breeding vermin,etc.).

Where public waste managementservices are at all available in urbanpoor settlements, they are usuallylimited to the collection of refusefrom central collection points, often atthe fringes of settlements which caneasily be accessed from the urbanstreet network. Typical solutionsconsist of the installation of containers

Dumping of waste in river beds or creeks/17/

Irregularly emptied refuse containers/19/

Dumping of waste in streets /18/

Limiting factors for efficient solid waste management in urban poorsettlements:

• missing formal recognition of settlements by responsiblepublic sector institutions (in most cases, municipalities)

• limited capacities of public waste management services;caused in particular by insufficient refuse collection costrecovery through user charges

• limited willingness and capacity of residents to pay usercharges for refuse collection

• difficult accessibility in many settlements (narrow streets inbad condition)

• few incentives for private informal refuse collection due tolimited recycling possibilities of waste material

24



Potentials

Due to the economic situation ofresidents, the amount of wastegenerated in urban poor settlementsis usually significantly lower than informal, wealthier parts of cities: allmaterials with any possible economicvalue are usually separated andrecycled. Organic matter, for example,is used to feed domestic animals, orthe animals “separate” it themselvesfrom the accumulated refuse.

In extremely poorsettlements: high level ofrecycling and low amountsof waste generated

In less consolidated poor settlements,recycling of waste generated insidethe settlement itself is usually anexception. Instead, residents of poorsettlements often collect recyclablematerials from wealthier urban areas.Sorting and preparation for recyclingis then done inside poor settlements,where often highly specialisedinformal recycling economies havedeveloped. In a few cases, whole

urban quarters have specialised in thecollection and recycling of waste, forexample, the Zabaleen settlements inCairo, or the waste collectorneighbourhoods in Metro Manila(Smoky Mountain and Payattas).

With the consolidation ofsettlements, wastecomposition changes andopens up new possibilitiesfor internal recycling

With increasing consolidation of aninformal settlement, which is usuallyaccompanied by growing wealth of itsresidents, the composition of wastechanges: changes in consumptionpatterns usually produce a higherproportion of recyclable wastecomponents as well. Even in formerlypoor residential quarters, e.g. in theolder, more consolidated favelas inBrazil, basic internal recyclingmethods have developed.

Informal Markets forRecycled Waste

Typical informally recycled materialsare metals (in particular non-ferrousmetals and large scrap items),reusable glass bottles and plasticcontainers, and, to a lesser extent,paper and cardboard.

Organic waste, plastic bags, thin sheetiron and steel scrap, and paper andtextile off-cuts are generally moredifficult to recycle.

As a rule, the development of privateinitiatives for recycling waste dependsless on the material available and itssuitability for recycling, than on thepractical possibilities of sellingrecycled materials to intermediateagents, or of reusing or furtherprocessing them within the settlementitself.

Recycling of organic waste components/20/

Living and working on a refuse dump site/21/

Informal recycling enterprise in ManshietNasser, Cairo /22/

Self-help: clearing refuse from a canal /23/

25



management to cope with theirtasks better, particularly withregard to supervising andcontrolling solid waste manage-ment initiatives at settlement level;

• to introduce consumption-oriented user charges as incentivesto reduce refuse. Such usercharges should be introduced in acareful and gradual manner inorder not to put too muchfinancial pressure on residents ofpoor neighbourhoods.

There is a wealth of examples andpositive experience of solid wastemanagement initiatives in urban poorsettlements worldwide, and a varietyof feasible and realistic technicalapproaches and solutions for thecollection, sorting, recycling and finaldisposal of waste have beendeveloped. Some of these exemplarysolutions as applied in particularcases, are described in the followingsections.

Conceptual Approaches

The characteristics of urban poorsettlements described earlier, largelydefine the possible scope forinitiatives and projects to improvesolid waste management. For verypoor and vulnerable target groups,whose main interest is to secure alivelihood, increasing their awarenessof the necessities of protecting theirhealth and the environment willgenerally not be enough. It will usuallybe more important to provideeconomic incentives as well.

Taking into consideration such factorsas poor target groups' limited capacityto pay, the general inefficiency ofpublic sector waste management andthe difficulties of achieving completecost recovery for solid wastemanagement services, only few basicapproaches will be realisticallyfeasible. As far as possible, they shouldbe combined or applied in acomplementary way:• to further reduce amounts of

waste by promoting better sortingand recycling;

• to demonstrate the economicfeasibility of waste recycling,supported by training and advisoryassistance;

• to mobilise the potentials forresident self-help and initiatives byother civil society stakeholders(e.g. NGOs) to solve the mosturgent and obvious solid wastemanagement problems;

• to promote and support informalsector micro-enterprises who areinterested in the businessopportunities offered by refusecollection and recycling activities;

• to enable public sector institutionsresponsible for solid waste

u The following sections of thischapter provide summaryoverviews on technical solutionsand processes that can beapplied in urban poorsettlements. In addition to adescription of their mainfeatures and characteristics,their appropriateness is assessedbased on the criteria presentedin chapter 1.

Where possible, the overviews arecomplemented by concreteexamples.

Private refuse collectors in Kenya /24/

26

Determining Factors for WasteAmounts and Composition

• geographical location

• ways of life andnutritional habits

• cultural and religiouscharacteristics

• urban or rural setting

• levels of income

• background

• timing (season,weekdays or holidays)


WASTE GENERATION

In order to conduct an analysis ofwaste generated and its amounts thatreflects settlement-specificcharacteristics clearly, the followingaspects should be considered:• The sample of households should

be large enough to derivesufficient representativeinformation. Depending onsettlement size and characteristics,generally 10-20% of all householdsshould be included (however, inextremely heterogeneoussettlements, the sample may haveto be significantly larger). Inaddition, the selection ofhouseholds to be included in thesample should adequately reflectthe neighbourhood's social andeconomic conditions.

Basic Concepts

The planning of solid waste collectionand disposal measures, and theidentification of waste sorting andrecycling options will usually have tobe based on a careful analysis of boththe amounts of waste generated andof its composition.

This is particularly relevant in urbanpoor settlements, where the amountsof waste and its composition arenormally considerably different to thatin formal, wealthier urban quarters. Inurban poor settlements, refusetypically consists of organic waste (upto 60-70 % vol.), paper (2-5 % vol.),plastics (mainly foil material, 2-5 %vol.), low-quality scrap (predominantlytin plate containers; 2-4 % vol.) and amix of stones, bones, textiles, brokenglass, batteries, etc. (20-25% vol.).

Given these general characteristics,amounts of waste and its compositioncan, in fact, vary considerably betweendifferent urban poor settlements indifferent regions or countries. Theymay be influenced by a settlement'slocation and other specifics, e.g. if it iscentrally located, or is relativelyconsolidated compared to a peri-urban settlement at the urban fringe,or by its climatic conditions, e.g. aridor tropical etc. Other factors, such asways of life, nutritional habits, religion,seasonal differences etc. may alsoimpact on waste amounts andcomposition.

TOOLS AND INSTRUMENTS FOR ASSESSING WASTE GENERATION

• In order to achieve an appropriatequality of fractioning, the sortingof waste components should bedone manually.

• Sample waste collections shouldbe done for different weekdays; toobtain reliable results, at least 4sample collections will benecessary for each weekday.

• To take seasonal differences inwaste amounts adequately intoaccount, waste samples should, ifpossible, also be collected fordifferent seasons.

• The information on wastefractions compiled can either bepresented as volume or weightpercentages, the latter being themost common form.

u More detailed information ontools and instruments foridentifying and analysing wasteamounts and composition can befound in, for example: in:Jaradat, Isam Sabri Yousef:Municipal Solid WasteManagement in Jordan/Aqaba(International Institute forInfrastructural, Hydraulic andEnvironmental Engineering –IHE, Delft, 1999)

Tools and Instruments

27


WASTE GENERATION

country characteristics total organic paper plastics metal glass other source of sample area amount material

t/p/a weight % weight % weight % weight % weight %% weight %Jordan Aqaba, high 0.11 61.4 13.6 9.7 7.9 4.9 2.5 (1)

incomeJordan Aqaba, low

income 0.05 70.1 9.2 8.1 2.4 2.1 8.1 (1)Mali Koulikoro,

city centre 0.12 93.1* 1.2 2.2 0.6 0.4 2.5 (2)Mali Koulikoro,

urban fringe 0.41 95.9** 0.8 1.2 0.6 0.2 1.3 (2)Argentina urban 0.18 55.4 10.8 6.0 4.8 11,4 11.6 (3)USA average 0.73 30.0 38.0 10.0 8.0 6.0 18.0 (4)Cyprus average 0.41 35.0 25.0 13.0 4.0 3.0 20.0 (5)Malaysia urban 0.34 48.0 30.0 9.8 4.6 n.a. 7.6 (6)Malaysia rural 0.23 63.7 11.7 7.0 6.4 n.a. 11.2 (6)Brazil Rio de Janeiro n.a. 34.0 27.0 13.0 3.0 2.0 11.0 (6)India Bangalore n.a. 42.6 16.5 6.7 1.5 2.9 29.8 (7)India Dehli 0.17 n.a. n.a. n.a. n.a. n.a. n.a. (8)Vietnam Ho Chi Minh City n.a. 77.5 0.6 0.5 0.3 0.02 20.9 (7)* 60% sand

** 74% sand

Examples of Waste Amounts and Fractions in Different Countries

The table below shows examples ofwaste amounts and fractions indifferent countries.

The figures relate to the average wasteamounts generated by households inresidential areas in the correspondingcountries or cities.

It should be noted that wastecomposition can change significantlyin residential and industrial orcommercial mixed uses areas.

Manual sorting to identify waste composition and fractions in Cotonou, Benin /25/

Schematic sketch drop-off system

Waste collection point in an in inner-urban informal settlement in St. Rita,Cotonou /26/

28


WASTE COLLECTION AND TRANSPORT

DROP-OFF SYSTEMS

Application

Drop-off systems are to beunderstood as methods of wastecollection in which involvedhouseholds bring either mixed or pre-sorted waste to centrally locatedcontainers or transitional storageplaces. These collection points areemptied at regular intervals either bymunicipal or or other public sectorinstitutions, or by private wastemanagement companies acting onbehalf of municipal or publicinstitutions.

Drop-off systems are especiallysuitable in districts that are difficult toaccess by vehicle: for example, onsteep gradients, with narrow, windingalleys or unpaved roads.

They have also established themselvesin places where for ethical-religious

(e.g. in Islamic countries), climatic (inhot regions) or spatial reasons (highpopulation density, multi-storeyhousing), it is not possible to storewaste in the home or on the property.In principle, drop-off systems alsoenable recyclable material, such aspaper, glass or metal, to be collectedseparately from other waste. In fact,waste separation already occursinformally in many poor settlements,but this depends on whether asuitable market for sorted wasteexists.

In most poor settlements, if anarrangement for waste collection isavailable at all, simple drop-offsystems are the typical method,although in most cases it is carried outvery erratically and unreliably.

Because waste is brought to collectionpoints by users themselves, andremoval is reduced to a few centralis-ed locations, drop-off systems haveproved themselves many times inpoor settlements, and are often arethe most suitable solution. In manycases, it is possible to achievesignificant improvements to existing,but badly functioning drop-offsystems, with relatively minor effort.

u Further information on sortingand recycling waste can be foundin section 2.4

Various container types

/27/ /28/ /29/

29



Organisation and Structure

Collection points should be set up inplaces that can be approached easilyby collection vehicles, for example onmain roads or central public openspaces.

They can be installed as eitherpermanent (e.g. brick or concrete) ormobile containers. The latter areeither emptied into refuse lorries atthe location or are replaced withempty containers and then driven towaste disposal sites.

Numbers and sizes of containersdepend on three key factors:• the quantity of waste accumulated

daily in the collection area;• the extent to which recyclable

material is reclaimed by wastecollectors;

• the intervals between emptyings.

Containers should be dimensioned insuch a way that they do not spill overduring the times between emptyings.In hot regions, daily emptying isadvisable. Since waste can self ignite,and is also often set on fire byresidents and youths, containersshould be made only from fireproofmaterials, such as metal, stone orconcrete.

To avoid waste being spread byanimals or the wind, containersshould have lids that shut properly,but that can also be opened easily bychildren or elderly people. In somecountries (India for example), animalsare even given access to collectionpoints deliberately: the organic wastethere provides them with fodder. This

reduces the volume of waste andthereby the disposal costs. An obviousdisadvantage is that the animalsspread residual waste around.

As a rule, residents should be able toaccess a collection point within 50-100m, or at the most, 250 m. If there arenot enough containers or they are toofar away, there is a danger that wastewill be deposited in other places, forexample, at the roadside, in drainagecanals, on empty sites, etc.

Design and Implementation

Central waste collection point in Nakuru, Kenya /30/

30



Yang Pu, Shanghai, ChinaWaste collection organised by neighbourhood committeesand local governmentResidents bring their waste to collection points, where collectors pick it up forfinal disposal. A feature in Yang Pu is the use of bicycle-rickshaws or push-cartsas “mobile collection points”. This service is being financed by user charges,which households pay directly to neighbourhood committees.

Lakeview Estate, Nakuru, KenyaDrop-off system organised by women's groupsThe informal settlement, “Lakeview Estate”, is located in the immediateneighbourhood of the Nakuru National Park, which is famous for its millions offlamingos. Separated from the park only by a fence, the settlement has about20,000 inhabitants. As the municipality of Nakuru was not able to collect thewaste generated in the settlement, residents had begun to dispose of refusealong streets and on public open spaces. Wind and torrential rainfalls alsodispersed the refuse into the adjacent National Park.

The Usafi Women Self-Help Group was founded to improve these unhygienicconditions and the pollution. Its members began to collect the refuse fromstreets and open spaces. Its organic fractions were composted. To facilitatemore organised waste collection, five central collection points were establishedwith support from World Wild Life Fund for Nature - WWF: these are smallroofed buildings that are accessed from staircases (see picture). This design waschosen to prevent refuse being blown away and to facilitate loading ontocollection vehicles.

Limitations and Restrictions

Waste containers that are open to thepublic are usually dirty andunhygienic. This is caused, amongother things, by users dumping theirwaste carelessly, and animals,especially cats and dogs, spreadingwaste around while they forage forfood.

Moreover, waste that is stored for toolong produces smell nuisances andattracts vermin, such as flies and rats.Frequent fires in containers and atcollecting points are another reasonfor smell nuisance and also damagethe environment.

Suitability for Self-help

Drop-off systems need the support oflocal residents. The system as a wholecan only work if individual users arewilling to go to the nearest containerinstead of throwing their waste overthe walls of their property ordisposing of it in some other randomway.

In many places, it is first necessary tomotivate people and foster a sense ofpersonal responsibility. This is wherecommunity associations and self-helpgroups play an important role.

DROP-OFF SYSTEMS

31



Main FeaturesIndividual transport of household refuse to central collection points orcontainers; collection and emptying by service providers

ApplicationSettlements with difficult access conditions (bad road networks, narrow alleys,steep slopes, etc.)

CostsLow (no house-to-house collection)

OperationsTransport to collection points organised individually; onwards transportationusually organised by self-help groups or local government

Interfaces Central collection points for transferring refuse for final disposal

AdvantagesRelatively inexpensive and affordable; applicable even in poor areas; largelyindependent of street conditions; suitable for self-help approaches;later development of sorting and recycling possible

DisadvantagesHighly dependant on the participation and support of individual households;volume-related user charges not possible (no incentives for waste reduction); nocontrol of waste and disposal quality at central collection points (individualresponsibility usually ends at the collection point)

To be ConsideredMaximum distances to collection points; regular and reliable emptying ofcollection points or containers is indispensable to avoid negative hygienic andenvironmental impacts.

Assessment of Costs

Costs for a drop-off system arise from:• purchasing the containers or

constructing collection points, andthe capital cost of collectionvehicles;

• repairs and maintenance ofcontainers or collection points;

• personnel costs of the assignedwaste management companiesand / or organisations;

• costs of waste removal anddumping (vehicle operating costs,dump fees, etc.).

The total costs of the system dependeventually on the density of thecontainer network, the materials usedand the amount of maintenanceinvolved, e.g. for emptying andcleaning.

Brick and concrete waste containersare cheaper than metal containers.But they can only be emptied by handand not by mechanical lifting andtilting devices.

In many developing countries, wagelevels are not very high, so personnelcosts are often not a significant factor.Because there is no way to verify howmuch waste individual householdsdeposit in containers, it is verydifficult to introduce volume-linkedcharges in drop off systems.

Therefore, it is only possible to chargeflat rates.

32



PICK-UP SYSTEMS


Pick-up systems can use bothmotorised or non-motorised forms oftransport.

They need appropriate householdrefuse containers, which can either beprovided by the service operator orpurchased individually by the usersthemselves. If household containersare provided by the service operator,they can be a basis for introducingvolume-related user charges.Standardisation of householdcontainers also allows for the use ofcollection vehicles equipped withsuitably corresponding lifting gear.

However, in urban poor settlementsstandardised household refusecontainers are rather the exception.Residents normally collect their refusein any possible receptacle, e.g. old oilbarrels, unused washtubs, plastic bags,etc. An interesting example inThailand is rubber waste bins madefrom old truck tyres. They come innear standardised sizes, and aremanufactured by enterprisesspecialising in tyre recycling; they canbe seen outside almost all houses inThailand's urban poor districts.

As a rule, refuse containers arenormally put out on the street to beemptied or picked-up once or twice aweek. In some cities, refuse is evencollected on a daily basis.

u A more detailed description ofmotorised and non-motorisedsystems is given in the followingsections.

Application

Pick-up systems are methods of wastecollection in which involvedhouseholds collect and temporallystore their refuse in appropriatecontainers, either inside the house oron the plot. The household wastecollected and stored individually isthen picked-up door-to-door bymunicipal or other public or privateservice providers.

Pick-up systems are the most typicaland wide-spread form of wastecollection in industrialised countries.In developing countries, pick-upsystems are usually only applied informal upper and middle-classresidential areas. Due to their highercosts and organisational requirementscompared to drop-off systems, fullyfledged pick-up systems are rare

exceptions in urban poor settlements.However, there are few examples ofsimplified pick-up systems whichdemonstrate that they can be a validoption for waste collection, even forpoor target groups, particularly inmore densely built-up settlements.

Schematic sketch pick-up system

33




The design of pick-up systems shouldbe based on actual waste amounts tobe collected door-to-door. Thecarrying capacity of motorised or non-motorised vehicles (e.g. push-carts,donkey carts etc.) should be sufficientto pick-up all waste in the particulardistrict or area to be serviced. Thedimensions and carrying capacities ofmotorised vehicles will also have toallow for whether refuse will betransported loosely or compacted.

Standardised household refusecontainers will have to dimensionedaccording to the waste amountsgenerated and temporarily stored byhouseholds prior to pick-up. Differentsizes combined with volume orweight-related user charges canprovide incentives for reducing wasteand for sorting out recyclable material.The collection frequency will have tobe coordinated with the householdsinvolved, taking into accounthousehold storage capacity andhygienic aspects.


Any pick-up system will need a suitablestandard of street network to allow ade-quate access to involved households. Asa minimum, households should at leastbe accessible by push-carts or donkeycarts. In more densely settled areas withmore developed internal street networks,the use of motorised vehicles may be anoption, depending on street conditionsand the financial capacities of residents.In most cases, however, these con-ditions do not exist. It will thus begenerally difficult to connect urban poorsettlements to formal municipal pick-upsystems, which usually use motorisedvehicles.

Pick-up systems can only function whencollection is reliable. Only then will usersbe willing to temporarily store theirrefuse rather than dumping it informallyoutside their plot or neighbourhood. Ifrefuse collection is organised as a privatesubscription service, only subscribinghouseholds will be serviced. But eventhen, fluctuations in payment patterns oroutstanding user charges can severelyaffect the economic viability andsustainability of such services.


In urban poor settlements that are notcovered by municipal wastemanagement services, self-helpinitiatives will be necessary to improvesanitary and hygienic conditions.Generally, such initiatives will aim tolink local waste collection to city-widecollection and disposal systems.

A valid and well-tested option for suchinitiatives is subscription basedsettlement level pick-up systems thatcan be operated by local NGOs,neighbourhood committees or small-scale enterprises.

To encourage participation in suchinitiatives, and to create sufficientawareness of the financial andoperational aspects, self-help groupsand community-based organisationswill usually have to take an active role.

Rubber refuse containers made fromtruck tyres, as widely used in Thailand,China and Laos /31/

Refuse collection in plastic bags inWindhoek, Namibia

/33/

Waste in various receptacles depositedfor street collection in St. Rita, Cotonou,Benin /32/

Refuse collection in Cotonou, Benin/34/

Badge indicating that the household is a subscriber to refuse collection services in St.Rita, Cotonou, Benin /35/

34



St. Rita, Cotonou, BeninDoor-to-door collection with push-cartsSt. Rita is a neighbourhood in the City of Cotonou with a predominantly poor population. Due to its location close to thelagoon and at almost sea level, parts of St. Rita are regularly flooded. The settlement is not supplied with Cotonoumunicipal waste management services. Residents thus deposited their refuse on streets, public spaces or vacant plots.Some even used it as fill for their house foundations or to elevate their plot for flood protection. This resulted in extremelyprecarious hygienic conditions with a high incidence of illnesses.

A local hospital, with financial support from external donors, therefore took the initiative and established an NGO with theobjective of developing a door-to-door refuse collection system. In addition to establishing technical and administrativestructures, the mobilisation of residents through training and awareness raising campaigns was an important part of theproject. As far as possible, the project was built on existing organisational structures (neighbourhood committees,assemblies of elders, political bodies, women's groups and youth associations). With the help of all stakeholders, it waspossible to introduce a monthly user charge of FCFA 1,000 (USD 1.5) for households that were willing to subscribe to thewaste collection service.

The settlement was then divided into different “collection districts”, in which refuse is collected by a team of two workerswith push-carts. The teams then bring the collected refuse to central transfer stations, where recyclable materials are partlyseparated out; the remainder is then transported to a central landfill site outside the urban area. The collection of monthlyuser charges was organised by resident committees in each collection district.

Once the system was established and operational, with 90% of households subscribing in some areas, the second step wasprivatisation of the collection districts: i.e. the refuse collectors were encouraged to work on their own account. With theprospect of increasing their income, the refuse workers, who now had to collect user charges themselves, were motivatedto increase the number of subscribers and improve the efficiency of fee collection. The NGO continues to supervise thequality of waste collection, facilitates the provision of push-carts and takes over the collected refuse at the central transferstations for sorting and final disposal.

High costs for transport from transfer stations to the landfill site remain a major problem. In a further phase, efforts torecycle waste components more systematically, and to reduce the amounts of waste to be transported for final disposal areto be increased.

PICK-UP SYSTEMS

35



Assessment of Costs

If no standardised domestic refusecontainers are provided by serviceoperators, which is usually the case inurban poor settlements, the followingcosts will have to be considered inorder to develop and establish asimple pick-up system:• purchasing costs for collection

vehicles;• energy/fuel and other operating

costs of collection vehicles;• personnel costs of refuse workers

and fee collection staff;• costs of refuse transport and final

disposal.

To be financially sustainable, thesecosts will have to be covered bycorresponding user charges.

The marketing of sorted and recycledwaste components may provideadditional revenue: but it may alsoentail additional costs, e.g. for sortingand storage of recyclable materials.

Main FeaturesDoor-to-door collection of refuse; transport to landfill site directly or fromtransfer station using larger trucks

ApplicationSettlements with minimum accessibility (or at least accessible for push-carts)

CostsRelatively high (due to individual door-to-door collection)

Operationsprivate enterprises, self-help initiatives or municipal

InterfacesTransfer of refuse collected locally by private enterprises or self-help groups tomunicipal or private operators for further transport and final disposal

AdvantagesCan provide job opportunities; volume or weight-related user charges arepossible; efficient control of final waste disposal; temporary storage of refuse byindividual households facilitates sorting, separation and composting

DisadvantagesNeeds a minimum of infrastructure; needs sufficient space for and socialacceptance of refuse storage inside houses or on plots; requires willingness topay for collection service

To be ConsideredRegular refuse pick-up is indispensable to maintain the trust of users in thesystem and their willingness to pay

Manual push-cart in Cotonou, Benin/36/

Donkey cart in Manshiet Nasser, Cairo,Egypt /37/

36



NON-MOTORISED SYSTEMS

Operations and Maintenance

Even the life span of simple, non-motorised collection vehicles will bedefined by their mode of operationand the quality of their maintenance.Their life span can be considerablyextended if overloading is avoided,and when moving parts and bearingsare regularly lubricated. Smalldamages should be repaired quicklybefore they lead to major problemsand long downtimes.

When animals are used, special careshould be taken to maintain theirhealth and strength. Good fodder,correct treatment of illnesses orinjuries and sufficiently longregeneration periods will be essential.Unfortunately, draught animals areoften held in low-esteem and illtreated. In Mali, for instance, it iscommon knowledge that donkeys,once they are used to pull waste carts,do not normally survive for more thantwo years.


Small payloads and short ranges limitthe possibilities of using non-motorised vehicles for wastecollection, particularly when heavy orbulky materials (e.g. cartons, plasticsheets or bulk rubbish) need to betransported. Moreover, in settlementswith steep slopes, the physicalstrength of men or beasts can often benot enough to move a loaded wastecollection vehicle.

Application

Non-motorised vehicles are usedwhen insufficient capital and badstreet conditions limit the use ofmotorised collection vehicles. Non-motorised systems are a simplesolution appropriate for most urbanpoor settlements (and also for ruraland peri-urban areas). There is awealth of examples and practicalexperience of their application.

Non-motorised systems can contributeto job creation and income opportuni-ties since they are labour intensiveand the payloads of the individualcollection vehicles are small andmanageable. Consumables needed foroperations (e.g. fodder for draughtanimals) are usually locally availableand can often be obtained free ofcharge. The usually simply con-structed vehicles have low investmentcosts, can be manufactured locally,and are easy to repair and maintain.


The kind and number of collectionvehicles needed mainly depends onresidential densities, the amounts ofrefuse generated, the condition of theinternal street network and the dis-tance to transfer stations or landfillsites. Payloads and distances shouldnot exceed the capacities of men andbeasts. Particularly during rainy sea-sons, when streets are muddy and wetrefuse is heavier, the risk of over-burdening is high.

Manual push-carts have a limited scopebecause they can only cover shortdistances. Bicycle rickshaws or animaldrawn carts, on the other hand, canallow for larger transport distances,possibly even to landfill sites, althoughconsiderable time-input may be neededdue to their low speed.

Collection districts or areas shouldthus be designated in ways that enablethem to be adequately covered by thetypes of vehicle available.

37




Due to their comparably lowinvestment and operating costs, theirlabour intensive operation and thepossibilities for local repair andmaintenance, non-motorised vehiclesare especially suitable for use in self-help initiatives. Moreover, they areoften the first step towards themechanisation of locally organisedwaste management systems. Theirpotentials can be demonstrated by thefact that, until a few years ago, all therefuse in the metropolis of Cairo wastransported by donkey carts.

Assessment of Costs

Necessary initial investments willlargely depend on the kind of vehiclesto be used and their technicalstandards. When they can beproduced locally, they will usually beaffordable to individual private refusecollectors, local self-help groups orsmall-scale enterprises. In addition toinitial purchasing costs, operatingcosts will normally consist ofmaintenance and repair costs, costsfor fodder and animal care, and staffwages. Depending on the refusecollection system, other expenses mayoccur for final disposal at a landfill siteor for the use of transfer stations.

Koulikoro, MaliModification of donkey carts to deal with particular wastecomponents

In the municipality of Koulikoro in Mali, which has 20,000 inhabitants, a smalllocal enterprise collects household refuse with donkey carts. Commissionedand licensed by the municipality, the enterprise collects user charges directlyfrom the households its serves.

Due to the lack of an organised landfill site, the refuse is dumped on thebanks of the river Niger outside the town. In the search for ways to reducethe amount of residual waste to be finally deposited, an analysis of wastecomposition was conducted.

The result of the analysis was that the refuse consisted of 60-75% sand.Separating the sand from the collected refuse could, therefore, considerablyreduce the weight and volume of waste to be deposited, and, at the sametime, relieve the strain on animals and collection vehicles. Because of the aridclimate, the easiest way to separate the sand was to sift the refuse.

To do this, a funnel with a sieve insert was designed that attached to the backof the donkey cart. The sifting process begins once the refuse is loaded intothe funnel, and increases when the cart moves forward. Since most urbanroads and streets are unpaved, the sand can usually be left where it where ithas been sifted.

Main FeaturesTransport of refuse with simplevehicles like push carts, animaldrawn carts or bicycle rickshaws in alabour-intensive way;

ApplicationSettlements with minimuminfrastructure: in cases where there isa lack of capital for largerinvestments or insufficient streetnetworks for motorised vehicles

CostsLow: local production; possibility oflocal repair and maintenance;manageable investment andmaintenance costs

OperationsSelf-help possible; individually ownedvehicles and self-employed oremployed personnel

InterfacesTemporary or final disposal needs tobe within the reach of vehicles;otherwise risk of uncontrolleddumping

AdvantagesLow investment and operating costs;simple operations; flexible; first stageof a more complex solid wastemanagement system; well-suited forself-help

DisadvantagesLow payload capacity, limited range

To be ConsideredLoads and transport distances shouldbe carefully adjusted to the capacitiesof men and beasts

Small refuse collection truck, Ecuador/38/

38



MOTORISED SYSTEMS


The selection of appropriate vehicleswill mainly be determined by thefinancial capacities of their operatorsand the quality of the existing internalstreet network. In most cases,especially in typical urban poorsettlements with narrow and windingalleys and rough street surfaces,inexpensive and sturdy motorisedvehicles will be the solution of choice.

Since the transport distance and thetime needed to get to landfills ordumping sites are often decisivefactors for operating costs, largervehicles with higher payloads willusually be given preference.

If street conditions inside a settlementprevent the use of larger vehicles,reloading refuse from smaller to largervehicles may have to be considered.This will require the establishment ofappropriate transfer stations, usuallyat the settlement fringes.

Application

Motorised vehicles are particularlyuseful when larger amounts of wastehave to be collected and transportedover longer distances.

For refuse collection purposes, thereis a large range of possible solutions:from simple motor rickshaws ortricycles, to small trucks, up totechnically sophisticated compactortrucks.

Larger vehicles with higher payloadcapacities can increase collectionefficiency considerably. On the otherhand, they usually need technicallyqualified staff and an appropriatestreet network. Costs for investment,operations and maintenance generallygrow in line with the increasing sizeand technical sophistication ofvehicles, while costs for personnelusually decrease. However, sincesalaries and wages are relatively low inmost developing countries, possiblesavings on personnel costs do notnormally compensate for higherinvestment costs.

For refuse collection in urban poorsettlements, the use of smallermotorised vehicles is often a validoption, and a wealth of practicalexperience and proven technicalsolutions are available.


The use of large, modern equipmentnormally requires specific technicalknow-how on its operation,maintenance and repair. Hencepersonal skills will have to built upand suitable garaging and workshoppremises will need to be found.

To extend vehicles' life spans, it willbe important not to exceed theirmaximum payloads and to servicethem regularly (renewing coolants, oil,hydraulic liquids, etc.). If second handvehicles imported from industrialisedcountries are to be used, specialproblems often arise with regard tothe supply of spare parts and withtechnical skills needed formaintenance. In addition, suchvehicles would, in some cases, have tobe suitable for particular climaticconditions (e.g. with sufficient enginecooling in extremely hot climates).

For hygienic reasons, a regular andcomprehensive cleaning of theloading spaces or holds of vehicles willbe necessary.


The main factors limiting the use ofmotorised collection and transportvehicles are usually the bad streetconditions in urban poor settlements,the lack of qualified maintenance andrepair staff, and difficulties withobtaining spare parts.

Due to the comparatively high costsinvolved in the purchase andoperations of motorised vehicles, theireconomic feasibility, including factorssuch as the financial capacities ofoperators, can also restrict their use.

Mini tractor in Lokossa, Benin /39/

39




Budget classes of motorised vehiclecan be appropriate for self-helpinitiatives, as investment andoperating costs will be moremanageable.

Buying larger, more modern vehiclescan easily exceed the financialcapacities of self-help initiatives. Sincemodern compactor trucks can oftencost hundreds of thousands of Euros,they would in most cases have to befinanced with support from externalresources. However, due to thefollow-up costs involved, their use inurban poor settlements should beconsidered very carefully, even whensuch resources are available.

Assessment of Costs

Necessary initial investment costs willgenerally increase with size, payloadand the technical equipment ofvehicles, and will be disproportionateto any resulting savings in personnelcosts. Overall economic feasibility willthus be mainly determined by thefixed costs of initial investments(interest payment, depreciation,discounting of equity). In com-parison, salaries and wages, which areusually low in developing countries,will be less important.

Increases of efficiency expected frommore sophisticated equipment shouldtherefore be really significant, andhigher investment costs should not bejustified by savings in comparativelyinexpensive labour costs.

Lokossa, BeninMotorised pick-up systemoperated by a cooperativeIn the provincial capital city ofLokossa in West African Benin, awaste management cooperative picksup household refuse in a door-to-door collection system, using a minitractor and trailer produced in China.A monthly user charge is collectedfrom all involved households, but thecharges do not completely cover theservice costs.

Refuse can be transported with themini tractor to a central collectionpoint outside the city boundaries,where it is sorted. Recyclablematerials, such as plastics, paper andmetal, are sold. Organic wastecomponents, which constitute 40-50% of the total refuse, arecomposted and then used forgardening and urban agriculture.Yields can thus be improvedconsiderably, and sales of fruit andvegetables at local markets havebecome a new source of income.Without the mini tractor, this wouldnot have been possible.

Main FeaturesTransport of refuse with motorisedvehicles with higher payload andtransport capacity

ApplicationIn settlements accessible for motorisedvehicles; particularly applicable for largeamounts of refuse or for transportingrefuse from drop-off system transferstations to final disposal sites

CostsHigh costs for investment andoperations

OperationsSimple or budget class motorisedvehicles possibly suitable for operat-ion s by self-help organisations orsmall-scale enterprises; larger, moremodern vehicles usually requiremore professional organisational set-ups and operations

Interfaces Operations of small-scale enterprises orself-help initiatives at settlement levelwill usually have to be complementedby city-wide (municipal) operationswith larger vehicles and higher payloadand transport capacities

AdvantagesEfficient transport of larger amountsof waste over longer distances

DisadvantagesHigh initial investment and long-termoperational costs; requires skilledpersonnel and minimum streetnetwork s quality

To be ConsideredRegular maintenance; avoidance ofoverloading

40


HANDLING OF REFUSE AND ITS FURTHER TREATMENT

RECYCLING OF HOUSEHOLD WASTE COMPONENTS: BASICCONCEPTS

In urban poor settlements, dealing with household refuse appropriately and itsfurther processing can be a practical option and complement conventionalcollection, transport and final disposal. Refuse sorting and separation canconsiderably reduce the amount of waste to be expensively transported for finaldisposal. Moreover, recyclable material can be further processed inside thesettlement, thus helping create new job opportunities and income.

Household refuse in poor residential areas often contains few recyclablecomponents, as any material of any value has usually been separated out of it.Recycling initiatives will therefore have to focus on those materials that areactually present in the household refuse of urban poor settlements. These aremainly organic matter, and paper and plastic components. Metal and glass arequantitatively and qualitatively less significant, since large metal parts, non-ferrous metals and intact glass bottles have usually already been separated out.Waste generated by local small-scale enterprises, industries or transport services(waste oil, tyres, batteries, metal scrap, textiles, wooden parts) can, in somecases, be a basis for recycling and further processing.

In most urban poor settlements, recycling and processing of waste materials,when it occurs, is generally part of the informal sector economy.

Unfortunately, due to lacking financial resources, technical know-how andawareness, many of the processes and techniques practiced by informalenterprises seriously affect both the environment and the health of peopleinvolved in recycling activities. Any plans to promote recycling initiatives shouldtherefore, on the one hand, avoid damaging existing economic structures andmarkets, and on the other hand, strive to limit or alleviate possible threats andhazards for people and the natural environment.

The economic success of recycling initiatives will largely depend on specificlocal conditions (e.g. markets or demands for recycled materials), which shouldbe carefully analysed and assessed in early preparatory stages.

u for check list for planning recycling measures, see Annex

Sorting of waste enables:• the extraction of recyclable

and marketable materialfrom refuse (secondary rawmaterials);

• the separation of hazardouswaste components (e.g.batteries, chemicals, etc.)

• the minimising of theamount of residual waste tobe deposited

SORTING

Application

Refuse sorting can be applied in urbanpoor settlements when householdrefuse contains sufficient quantities ofrecyclable materials, and when resi-dents are interested and willing toembark on sorting and recyclinginitiatives.

Ideally, refuse sorting should be donedirectly at its source in individualhouseholds or commercial enter-prises; but, for various reasons (lack ofspace, insufficient acceptance, culturalreservations, ignorance, etc.), this willoften not be practical, or only bepossible when appropriate incentivesare available (e.g. payment, marketingpossibilities for secondary rawmaterials, etc.). Even when householdlevel separation and sorting doesfunction, an amount of mixed refusewill always remain to be sorted andfurther processed in order to separaterecyclable material from more hazard-ous components and other residuals.

Although significantly morechallenging, sorting and separation ofrefuse after household collection isalso possible. This is usually done atcentral locations or sorting stationsespecially established for the purpose.

Sorting refuse in an inner-city informal settlement in Cairo, Egypt /40/

41




Depending on the daily amounts andvolumes of refuse generated, sortingcan be done manually, be partlymechanised or be completelymechanical. In urban poor settle-ments, partly mechanised sorting will,in most cases, be the maximumfeasible option. But because labourcosts are low, it will usually makesense for sorting to be done as muchas possible by hand.

The following main processing stepswill be necessary:• sieving, to separate coarse and fine

waste fractions;• manual sorting of coarse and fine

fractions with the objective of:- extracting recyclable material

from coarse fractions (paper,plastics, metal, glass),

- cleaning organic fractions(which are usually the majorparts of the fine fractions).

Effective sorting can reduce theamount of residual waste to be finallydeposited to less than 20% of theoriginal volume. A recycling of organicfractions and of paper and plasticcomponents will be particularlyimportant.

Quantities, Design andImplementation

Household refuse of up to 5 tons perday (from a catchment area of 15,000 -20,000 inhabitants) can be sorted andseparated completely manually. Apartfrom a paved surface (e.g. a concreteslab with an area of ca. 10x10 m), theonly equipment needed will be a largesieve. Ideally, the sorting area shouldbe fenced or walled to prevent refusebeing blown away or the theft ofvaluable waste components.Containers to store different recycledmaterials will be useful. Five peoplewill be needed to separate and sortthis quantity of refuse.

For up to 20 tons of refuse per day(from a catchment area of roughly 60 -80,000 residents), a partly mechanisedsorting system may be moreappropriate. Its main elements are aconveyor belt to transport the refuseto a drum sieve, and two other beltsfor manual separation of coarse andfine fractions. Moving both incomingrefuse and the extracted fractions canbe done by a motorised shovel. Again,the sorting installations should befenced, or, even better, be locatedinside a work hall. To operate theequipment and to sort this amount ofrefuse, about 10-12 persons will beneeded.

Operations

To avoid nuisance from smells,incoming refuse should be processedon the same day, or, at the latest, onthe following day. Residual refuseshould be transported for finaldisposal immediately. In most cases,the extracted materials will needfurther procession, which can be doneeither at the sorting area or at othersuitable locations.

To protect staff, the sorting area andits premises should be well-aired.Protective clothing, including glovesand dust masks, should be provided,as should basic washing facilities.Eating should be prohibited inside thesorting area.

The sorting area should be fenced orwalled to avoid refuse being blownaway or dispersed by animals.

u Further information on differentrecyclable materials are providedin the following sections

42



Cairo, EgyptWaste sorting by Coptic refuse collectors - the Zabaleen of Cairo

A part of Manshiet Nasser, with roughly 400,000 inhabitants, is one of the largest informal settlements in the Egyptiancapital Cairo, and is located close to the historic Islamic city. It is populated almost exclusively by Coptic Christians. Mostof its residents make a living by collecting, sorting and processing household refuse from wealthier parts of Cairo. In total,about 10,000 people in this particular part of Manshiet Nasser are working and living with refuse. In addition to raising feesfrom households, the recycling of refuse, which used to be collected with donkey carts, and today is done with smalltrucks as well, is traditionally their most important income source. Over time, a whole economy, with complex sorting andrecycling systems, has developed, which nowadays is even used by public sector refuse collection providers. In addition torefuse delivered by donkey carts and small trucks, even large municipal collector trucks discharge their loads for sortingand recycling.

Incoming refuse is usually manually sorted by women and children. Organic components are fed to pigs and goats kept bythe Christian residents. Paper, plastics, textiles and metals are sorted by material, colour and quality, and then sold toother families who have the necessary equipment and technical skills to further clean, shred, ameliorate and process bulkrecycled materials. In this way, the neighbourhood not only produces intermediate products, such as bundled paper andsorted plastic waste, but also final products like metal cast goods, die-cast plastic parts or cushions made from textilewaste.

Even machines and equipment needed for recycling and processing (baling presses, shredders, plastic extruders, die-casting machines, etc.) are nowadays partially or completely produced inside the settlement.

SORTING


To avoid long transport distances,sorting should preferably been donewhere the waste is generated. Thisoften conflicts with a limitedavailabilities of space or the wishes ofresidents, who often do not wantrefuse sorted in their immediateneighbourhood. In many countries,the handling of refuse has a negativeimage; in others, this work isrestricted to certain ethnic groups orcastes.

In general, negative impacts andnuisances of refuse sorting andprocessing cannot be completedavoided. Thus speedy processing andappropriate protection measures willbe important.


In general, individual sorting at house-hold level has considerable self-helppotential. Negative environmentalimpacts and nuisances often causedby central waste sorting can thus beavoided, and households can benefitdirectly from the possible revenuesfrom selling of recycled refusecomponents. Moreover, costs for thecollection and disposal of residualrefuse can be significantly reduced,again to the direct benefit ofindividual households.

Initiating and promoting waste sortingat household level will generallyrequire educational or awarenessraising activities. Community basedorganisations, environmentalinitiatives or self-help groups can be

instrumental in this. Often a practicaldemonstration of sorting possibilitieswill have to be given before they willbe adopted by individual residentsand households.

In most cases, both individualawareness raising and practicaldemonstrations of refuse separation,will have to be undertaken in parallel.

Batteries separated from householdrefuse in Cotonou, Benin /41/

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Assessment of Costs

Individual household refuseseparation does not normally entailany significant costs. It only requires alittle time input, and can evengenerate additional income.

Completely manual sorting of mixedhousehold refuse needs only minorinvestment for installations andequipment - a sorting area, fencing orwalling, sieves, shovels and somecontainers or bags for the differentrecycled fractions. Basic equipment,space or premises are, moreover,often readily available inside settle-ments, thus reducing, or doing awaywith some of the initial investmentsneeded. The only operating costsincurred will be for workers' wages.

Partly mechanised sorting will requiremore substantial investments in equip-ment and installations. Depending ontechnical specifications, these canquickly add up to some tens ofthousands of USD. Such investmentswill only be justified when largeamounts of refuse are to be pro-cessed, and sufficient recyclablematerial can be extracted.

Refuse sorting in Cotonou, Benin/42/

Main FeaturesExtraction of recyclable material and separation of hazardous waste fromhousehold or commercial refuse; preferably at source (households orenterprises); sorting after collection requires space and protection measures

ApplicationWell-suited for self-help approaches, as marketable products can be extracted,residual refuse reduced and hazardous waste separately treated and disposed of

CostsNo additional costs for sorting at source; main costs of manual sorting are for staffwages; sorting larger amounts of refuse can mean significant investment costs

OperationsWell-suited for self-help initiatives or small-scale enterprises, in particular whensorting is done by individual households or at collection places

Interfaces Larger volumes of residual waste accumulated after sorting have to be handed-over and transported for final disposal

AdvantagesCosts of sorting can be partly or completely financed by marketing recyclablecomponents

DisadvantagesRequires awareness, skills and acceptance of users; markets and marketingpossibilities are required

To be ConsideredThe better sorted and cleaner the extracted fractions, the higher the possiblerevenue from from their sale.

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Application

In developing countries, more than50% of total household refuse typicallyconsists of organic material. Compost-ing of organic components can there-fore contribute significantly to reduc-ing the amount of waste to be trans-ported and disposed of. Usually, themore rural the location, or the poorerthe inhabitants, the higher theamount of organic waste components.

Composting not only reduces theamounts of refuse to be disposed of,but it also produces valuable fertiliserthat can be used for gardening oragriculture, or for public open spacesin and outside settlements.

However, composting is still new andrelatively untested in solid wastemanagement projects in urban poorsettlements, where, in many countries,residents have grown up in urbanenvironments, and thus usually havelittle knowledge of a procedurederived from horticulture andagriculture.

Introducing composting schemes willtherefore normally need intensive ad-visory assistance, training and testing.

Composting can be done bothindividually at household level, and/orin central community or municipallevel facilities.

The advantage of composting athousehold level is that organic wastecomponents can be separated atsource, thus avoiding thecontamination of other wastecomponents that could be furthersorted and recycled.

Central composting allows for moreprofessional operations, with regularcontrol of humidity, temperature, thelevel of bacteriological sterilisationand the overall quality of the compost.Treatment of larger amounts ofmaterial usually requires appropriateequipment or machines, such asmotorised shovels, drum sieves orshredders.

Processing Features

In contrast to anaerobic fermentation,which produces biogas, composting isan aerobic process, which involves theintake of oxygen. To enable sufficientoxygen to enter the compostingmaterial, or “rot”, organic waste withlow fibre content and few carbon/nitrogen (C/N)components (e.g.kitchen waste, faeces etc.) is mixedwith waste with a higher fibre and C/Ncontent, which is also known as“structural material” (e.g. gardenwaste, twigs and chippings, etc.).Turning the compost over regularlyimproves the oxygen supply. In thecomposting process, the temperaturein the rot increases and killspathogenic germs. A correctly appliedcomposting technique can evenprocess faeces into hygienic and germ-free compost.

A second important factor is humidity,which is needed so that compostingbacteria become active. In hot dryclimates, regular control of themoisture content inside the rot will bevery important. In cold regions, asufficiently high temperature will haveto be maintained (e.g. by usingsuitably large compost pits).

Individual composting can be done,for instance, in special “compost bins”which have a sufficient number ofopenings or holes to allow air, andhence oxygen to enter. Centralcomposting is usually done in form ofconical or frectangular heaps erectedon levelled surfaces, sometimes madeof concrete.

In more specialised processes, thecompost is additionally ventilated orrotated in drums to speed-up thecomposting process.

COMPOSTING

Compost rots in Cotonou, Benin /43/

Different conical compost rots /44/

Sieving composted components fromhousehold refuse in old informaldumping sites in Mogadishu,Mocambique /45/

45




As a rule, the percentage of waterinside the rot should be 40-60% inorder to ensure a sufficient level ofhumidity. At the peak of fermentation,the temperature can rise to up to65°C. A drop in temperature indicatesthe transition from the aerobic to theanaerobic process, and the need toturn the rot over again. The period oftime between two turnings overmainly depends on climatic conditionsand cannot be generally determined.Followed fast decomposition in theinitial phases (1-2 months, called the“main rot”) the process slows down.The so-called “follow-up rot” can takean additional 2-4 months or more.

At the end of the process, thecompost has an earthy, humus-like

smell, and can be used or marketed asfertiliser or soil improver. Beforemarketing, another sieving processmay be necessary to separate outremaining solid parts (plastic, glass,stones etc.) or incompletelydecomposed components from thecompost. These can be re-used as“structural material” for new rots.

Design

The illustration below shows three kinds of simple conical rots; one without anoxygen supply channel, one with passive ventilation and a third with forcedventilation.


Simple composting processes can bedone with little equipment or machi-nery, but require a basic knowledge ofand experience with the underlyingbiological processes. Both individualcomposting and more complex centralcomposting will need a phase oftesting and experimentation. Possibleoperators should therefore havemotivation and constancy, as well asthe courage to experiment.

In many countries, compost is not yetcommon as a marketable product, soselling it can be difficult. It maytherefore be helpful to initially usecompost for personal requirements,or, for example, for fertilising publicgardens, to demonstrate its usage andprovide a basis for later marketing.

Checking the temperature of compost at the Dandora dumping site in Nairobi, Kenya/47/

46




Composting, with its low level oftechnical requirements, is well-suitedfor self-help approaches, which cansignificantly reduce waste generationand, at the same time, produceinexpensive fertiliser for gardeningand agriculture. Even with very limitedspace, plastic bags filled with compostcan be used to grow vegetables.

In many countries, compostinginitiatives can build on the localknowledge of traditionally ruralsocieties. Additional skills andknowledge on how to produce anduse compost can be disseminated byneighbourhood committees and self-help groups.

COMPOSTING

Bamako, MaliComposting by a private initiativeThe private initiative G.I.E. BESEYA separates and further processes organicwaste components at a waste transfer station. The organic material is thencomposted in covered pits.

The compost produced is manually sieved and then sold. G.I.E. BESEYA has alsoestablished a tree nursery, and compost is used to fertilise fruit trees; theharvest is sold.

G.I.E. BESEYA employs a number of young men and women who had problemsfinding alternative employment.

Nairobi, KenyaComposting by a self-help groupIn Nairobi, some hundred families live at the municipal dumping site ofDandora. They make a living by searching the waste for recyclable materials,which are then sold. One of the self-help initiatives, the Mboela Group, usesorganic waste components for small-scale composting. The group, supported bya neighbouring church, has learned to set up compost rots with the necessarymix of structural and fine material. The composting process is controlled bychecking the temperatures inside the rot regularly, using a wooden stick whichis inserted into the rot (see photo). After a certain time, the stick is withdrawnand the temperature checked by hand. If a sinking temperature indicates aninsufficient air supply, the rot is turned over. This is repeated until thecomposting process stops (i.e. when there is no further increase oftemperature). The compost is then sieved, filled into bags and sold, or used inthe group's own adjacent garden.

Plastic planting bag filled with compostfor growing vegetables in Kisumu, Kenya/46/

Compost heaps /48/

Manually operated drum sieve for sifting compost /49/

47



Assessment of Costs

The investment needed for compost-ing will largely depend on the scaleand scope of an initiative or project. Itcan range from almost no costs forindividual composting at householdlevel, to the purchase of motorisedshovels, shredders, sieving andventilation equipment, up to invest-ment in completely mechanisedcomposting plants.

Community self-help initiatives willrequire comparatively small invest-ments. If composting cannot be donecompletely manually, simple drumsieves, small shredders and motorisedshovels can be useful.

Main FeaturesAerobic fermentation of organic substances by bacteria and compost worms

ApplicationIndividually at household level or at central composting facilities

CostsLow costs for individual composting; investment and operating costs ofmachines and other equipment for larger volumes of material

OperationsIndividual and small-scale central composting facilities are well-suited for self-help initiatives; larger facilities are usually operated by municipalities or otherinstitutions

InterfacesDepends on the amount of organic waste to be composted

AdvantagesReduction of residual waste to be transported and deposited on landfill sites;production of valuable fertiliser; low investment needs; local knowledge of ruralsocieties can be built on

DisadvantagesRequires separation of organic waste components; marketing and theacceptance of composting by the population can be difficult; requires basicunderstanding of underlying biological processes.

To be ConsideredDepending on climatic conditions, special control of humidity levels andtemperatures is necessary

Large-scale industrial paper recycling at “Zülpich Paper Mill” in Germany /50/

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Application

Paper is generally the most commonwaste fraction in urban poor settle-ments after organic components. Withtheir long fibre content, cardboardpackaging is usually the most valuablematerial for recycling. Separation atsource (e.g. by using containers forpaper) will facilitate recycling. Re-cyclable and marketable papermaterial can also be extracted frommixed refuse. Cleaner paper com-ponents can be extracted and recycledas paper, while extremely soiled papermaterial can possibly be used forcomposting.

The production of recycled papergoods requires rather complextechnical installations and equipment.In most cases, even in developingcountries, paper is therefore recycledindustrially in large paper factories.Small-scale suppliers and enterprisesare mainly limited to sorting differentpaper qualities and pressingtransportable bales.

Small-scale industrial recycling pro-cesses can include the production ofhandmade paper, egg and fruitpackaging and pressed paper

Technical Solutions

Three basic technical solutions can beapplied for paper recycling activities atsettlement level:• sorting and compacting by baling

presses to supply material forfurther processing at a larger scale;

• processing on the spot, using so-called “pulpers” to produce eggand fruit packaging;

• the production of paper briquettesas fuel for heating and cooking.

Sorting and Compacting

The most important piece ofequipment for paper collectors andsuppliers to larger industries is abaling press. It is used to compactpaper into bales that can betransported at feasible costs.

Baling presses are available in differentforms and sizes, e.g. with worm driveshafts for manual operations or withhydraulic drives. Higher pressurehydraulic presses generally producemore compact bales and hence areduction of the volumes to betransported. Bale sizes should bechosen so that available equipmentcan move, load and transport them.

For sorting purposes, different paperqualities (e.g. cardboard packaging,office paper, magazines andnewspapers, laminates, coated paper,etc.) will have to be considered. Tomarket sorted paper, information onthe expected quality and compositionof the sorted paper should beobtained from potential wholesalebuyers or end-product manufacturers(paper mills). As a rule, sorted

SORTING AND RECYCLING OF PAPER

briquettes for domestic or industrialheating. In industrialised countries,paper shavings are treated with fire-resisting chemicals and used asinsulation for buildings. Papershavings can also be used as animallitter.

Paper separated in urban poorsettlements can supply both large-scale industrial recycling plants andsmall-scale settlement level recyclingenterprises.

Collecting, sorting and pressing scrappaper are common activities,practiced globally by large numbers offormal and informal collectors andtraders.

The production of handmade paper isalso quite common. A more recentand innovative recycling process is theproduction of paper briquettes forfuel. The manufacturing of egg andfruit packaging requires machineryand technical equipment, and henceonly large-scale production will beeconomically feasible.

Production of handmade paper inManshiet Nasser in Cairo, Egypt /52/

49



Processing for ProducingEgg and Fruit Packaging

To produce egg or fruit packaging,scrap paper (preferably fromnewspapers) is turned into paper pulpin a so-called “pulper”. A vacuumgenerated by the machine sucks thepulp into a mould and excess water isdrained off. The remaining still wetproduct is taken from the mould, anddried in the air or in a heated dryingcabinet.

Egg and fruit package production canbe done at different scales. Dependingon the amount to be produced,packaging can be manufacturedintermittently with simple smallmachines or, continuously, bycompletely automated productionlines. Egg and fruit packaging can bemade from relatively low-qualitypaper, and can contain a certainamount of soiled paper and othermaterial.

cardboard packaging, the mostimportant fraction, is usually allowedto contain 20-30% of other papertypes. A certain amount of soiledpaper or other material, such asadhesive tapes, cords, wires or plasticbinding is usually tolerable.

Pressing involves putting cardboardinto the press in layers, and thencompacted it. The resulting bales arethen tied with cords, wires or plasticstrips.

Production of HandmadePaper

The production of handmade paperbasically involves the same steps andprocesses that are used in large-scaleindustrial paper recycling. Theseinvolve:• shredding sorted scrap paper;• soaking;• producing paper fibre pulp in a

pulper and/or a beater;• removing the usable paper

components from the pulp using asieve;

• laying the wet sheets of paper on acloth;

• pressing the paper sheets to drainof the excess of water;

• drying;• possibly dying and further

processing.

Paper press in Manshiet Nasser in Cairo,Egypt /51/

50

Nairobi, KenyaPaper recycling in slumsettlementsThe local NGO, Undungu Society,promotes and supports paperrecycling and the production ofpaper briquettes as alternative fuel invarious slums of Nairobi.

For this purpose, 80 previousscavengers at the Dandora dumpingsite, called the Jumuiya Group, weretrained to operate two presses.

Scrap paper is processed intobriquettes with a simple manualpress. Although theoretically 100%paper could be used, only 30% paperis used together with 70% of otherorganic materials (charcoal dust,sawdust, bark mulch, carpentrychippings, etc.) to avoid generatingtoo much smoke from burning paperonly. The paper and othercomponents are first soaked for 24hours and then thoroughly mixed.The mixture is then slightlycompacted in one of the handpresses; its final stability is achievedonly after air drying. The briquettesare mainly held together by paperfibres which bind to the othercomponents in the same way as inthe original paper.

The briquettes are 15 cm long with adiameter of 10 cm. They are sold for1 KSH (about 0.02 USD) a piece.

Improvement of briquette qualityand wider sales are planned.




The possibilities of recycling wastepaper in an economically feasible wayare primarily determined by qualitystandards and the capacities of localor national markets.

Due to the low specific gravity ofpaper and cardboard, and relativelylow revenue from sales, long transportdistances will usually have a negativeeffect on the economic feasibility ofrecycling.

Paper briquettes have not yet becomecommon as an alternative fuel, andwill normally need special marketingefforts and campaigns. Moreover, theyare highly sensitive to moisture. Whenwet, they begin to swell and to losetheir solidity and stability. Paperbriquettes should therefore be storedin dry places, and, if necessary, packedin water-proof material (e.g. plasticbags).

Production of PaperBriquettes

To produce paper briquettes, shreddedpaper is hydraulically compacted topaper bars that are stable in form andstorable (in dry environments). Bri-quette presses can be operated bothcontinuously or discontinuously, e.g.only for a few hours at a time. Thesmallest production equipment current-ly available on the market can processabout 50 kg of briquettes per hour.

It is possible to press fuel briquettesfrom almost all paper types, and alsofrom extremely soiled sorts of paperthat are otherwise difficult to market.With mechanised pressing, the pro-portion of sand in the paper to bepressed will have to be limited, sincesand can cause considerable wear andtear in the machines. Before pressing,the paper has to be shredded and,depending on the type of press, madeslightly wet. In industrialised countries,dry pressing procedures are used todispose of files and paper records.These kinds of presses are less com-mon in developing countries, wherewet pressing techniques, as describedby the Kenyan case study on this page,will generally be more applicable.

SORTING AND RECYCLING OF PAPER

Manual production of fuel briquettes from 30% scrap paper and 70% charcoal dust inNairobi, Kenya /53/

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Due to the low investment requiredfor collecting, sorting and pressingscrap paper in urban poorsettlements, these activities aretypically taken up by small, mainlyinformal enterprises.

Although the production of egg andfruit packaging does require somebasic investment, it can still be done atthe level of small industries andenterprises.

The manufacturing of paperbriquettes can be useful in situationswhere fuel scarcities can create ademand that self-help initiatives couldcater for.

Assessment of Costs

The costs of recycling waste paperlargely depend on the scale ofproduction and on the type and originof machines and other equipment(e.g. paper recycling machines aregenerally much cheaper in India thanin Europe). For collection, sorting andmarketing, additional costs fortransport and staff wages have to beincluded.

A simple baling press can bepurchased in Egypt for 5-6,000 USD;manually operated paper briquettepresses can be produced locally forroughly 500 USD. In contrast,mechanical briquette presses orproduction equipment for egg andfruit packaging can easily cost up to50,000 EUR.

Hydraulic briquette press /54/

Main FeaturesCollection, sorting and processing of scrap paper into intermediate (e.g. paperbales) or final products (e.g. handmade paper, egg or fruit packaging, fuelbriquettes, etc.)

ApplicationWhen a market for recycled paper exists and appropriate small-scale technologyis accessible

CostsManageable investment costs for collection, sorting and bale pressing; forfurther processing, costs usually increase with volumes and the quality of goodsto be produced

OperationsAt small-scale industrial level, suitable for self-help initiatives and smallenterprises

InterfaceMarketing to wholesale buyers and further processing outside the settlement

AdvantagesMarketable goods from waste with relatively low need for equipment andmachinery; creates income and jobs at small-scale industrial level;environmentally friendly

DisadvantagesDue to the low weight and large volume of paper involved, transport is animportant cost factor

To be ConsideredSeparation of paper at source is recommended to avoid contamination fromother possibly soiled waste components

Locally manufactured mill for grindinghard plastic in Cairo, Egypt /55/

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Application

Plastics are the third importantcomponent of household waste. Inurban poor settlements, its amount, asa percentage of the total wasteproduced, usually increases with thegrowing wealth of residents over time.In older, more consolidatedsettlements, where residents havedeveloped relatively stable sources ofincome, significant volumes of plasticwaste can be generated. Its processingat small-scale industrial level cancreate new income sources andcontribute to the reduction of residualwaste to be disposed of.

Various processes for the recycling ofplastics have existed for a number ofyears at small-scale industrial level, butthey have not yet been applied ortested at a larger scale in urban poorsettlements.

As with other waste components,recycling of plastic waste will onlymake sense when there is a realmarket for recycled products, andwhen the necessary technicalequipment is available or accessible.Nevertheless, practical experience inmany countries, e.g. Egypt, India,Brazil and some African countries, hasshown that recycling plastics cancreate jobs and income in the informalsector.

Technical Solutions

Of the large number of modernsynthetic materials, PE, PP, PET, PVCand PS are the most commonly foundin household waste. Plastic foils, e.g.shopping bags made frompolyethylene (PE), are especiallyappropriate for small-scale industrial

recycling, as are containers andmoulded objects made frompolypropylene (PP), as well as tubesand other moulded items, such as thesoles of shoes etc., made frompolyvinyl chloride (PVC).

In small-scale industrial processing,plastic waste components aremanually separated and sorted, ifpossible, directly at their source inhouseholds, shops or commercialenterprises. In most cases, foilmaterial and moulded items andcontainers are collected separately.When plastics have to be separatedfrom mixed refuse, it will usually haveto be cleaned.

Small-scale industrial recycling usuallyconsists of collection, sorting,cleaning, shredding, agglomerationand granulation. In some cases, it mayalso involve the manufacturing of newproducts.

The descriptions in this section referonly to the production of thefollowing main intermediate productsof plastics recycling:• plastic chippings;• foil agglomerates;• granulate.

These are the results of the first stagesof plastic waste processing, and canbe produced at small-scale industriallevel with relatively little investmentand basic technical skills. All threeintermediate products can be used asraw material to make a number of newplastic goods.

SORTING AND RECYCLING OF PLASTICS



Production of PlasticsChippings

Hard plastic material and parts can betransformed into marketable inter-mediate products with shredding orgrinding mills. This can be done eitheras a dry or wet process. The wet processsimultaneously cleans the material.

Thick plastic chippings (in contrast tothin foils) are further processed eitherdirectly, or following an intermediategranulation stage, in screw extruders(see “Production of Granulate” below).These melt the material and process itfor use in the making of injection orblow-moulded products.

Depending on size and capacity, pricesfor shredder mills generally start at USD3,000. Their operation is rather simpleand does not require special technicalskills.

The wearing parts of shredder mills aretheir knives, which have to be regularlyre-sharpened, and after a given operat-ing time, will need to be replaced.

Agglomerator for foil waste56/

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Production of FoilAgglomerate

Foil agglomerate is produced in socalled “pot agglomerators”, whichwork in a similar way to kitchenmixers. Knives at the bottom of themachines rotate at high speed andshred the inserted foils. The heatgenerated in the process melts theplastic chippings and agglomeratesthem into irregular particles, whichare transported to further processingmachines (extruders) through asimple funnel.

Agglomerators have a high energyconsumption. Their economic feasibili-ty therefore largely depends on localenergy prices. Their operation requiresa certain amount of practical experien-ce in order to decide when the ag-glomerate has reached the correctconsistency to be removed.

Simple agglomerators, e.g. of Indianorigin, can be purchased at pricesstarting at USD 5,000. They are alsoproduced in many other countries.

Production of Granulate

To produce granulate, intermediaterecycled plastic products, e.g. cleanedplastic foils or shredded hard plasticchippings, are melted in a screwextruder and then continuouslyextruded as plastic strings, so-called“spaghettis”. After cooling andhardening, the spaghettis are choppedinto small granular pieces.

Granulation has the advantage that,through melting and mixing in theextruder, it results in a homogeneousproduct that is well-suited for furtherprocessing. Particular qualities ofplastic can be achieved by introducingappropriate additives (colour,stabilisers, other primary plasticgranulate etc.). Operating a granulatorpresupposes some basic technicalskills, which can be acquired relativelyeasily. Prices for complete granulationequipment start at USD 15,000. .

Sizing and Processes

Plastic goods typically have lowweights and large volumes. To extractsufficient plastic material in terms ofweight, significant amounts of plasticbags and other plastic items need tobe separated from other waste. Forsmall-scale industrial recycling, theprocessing capacity of machinesshould therefore correspond to thevolume of plastic that can realisticallybe collected. Machines made inindustrialising countries (e.g. India,Brazil, China) are usually suitable foruse in developing countries with lowcollection and processing capacities.The smallest machines available in themarket can process about 20 - 30 kg ofplastic waste per hour.

As a precondition for recycling,different types of plastics have to beseparated since they generally cannotbe processed jointly. The onlyexceptions are PE and PP plastics inspecific applications. Separation of PE,PP and PVC is not an easy taskbecause they look very similar. The so-called “swim-sink-separationtechnique” makes the separation of PEand PP from PVC easier. To do this,plastic chippings are put into water.Because they have different densities,the PE and PP fractions float upwards,while the PVC sinks to the bottom.

Due to their large surfaces and smallvolume, swim-sink-separation cannotbe applied to plastic foils. They canonly be sorted and separatedaccording to their appearance andmaterial characteristics.

The use of wet grinding mills will beuseful in the recycling plasticcontainers and moulded items, as thematerial gets rinsed and cleaned inthe grinding process; but anadditional drying stage will then be

Granulation equipment manufactured inIndia /57/

Sun drying of plastic chippings in Kisumu, Kenya /58/

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The possibilities of recycling plasticmaterials from household refuse aremainly determined by the degree towhich they are soiled.

In most cases, it will not be useful toprocess extremely soiled plastic foilsor containers since cleaning themwould be too demanding (consumpt-ion of water and detergents) and thequality of the end product would beinferior.


The technical challenges of plasticrecycling generally call for an initialphase of learning and training. Self-help groups or initiatives can play animportant role in facilitating andpromoting plastic recycling byinforming residents on its potentialbenefits and the possibilities ofcontributing at household level(sorting, cleaning, etc.)

SORTING AND RECYCLING OF PLASTICS

Kisumu, KenyaProfitable plastic recycling The Nyalenda Plastic Recycling Project in Kisumu, Kenya was established someyears ago and was based on the initiative of a local Catholic Church and aGerman development worker. Its objective was to work against the increasingenvironmental pollution caused by plastic waste and to create new jobs in theNyalenda neighbourhood.

The project buys hard plastic material from individuals, waste collectiongroups and intermediate traders. The plastic waste is sorted at the project'sown compound by colour and material (LDPE, HDPE, PP) and by type ofproduction (injection or blow moulding). The sorted material is shredded in amill, and then rinsed a couple of times. It is then dried in the sun, filled intobags and sold to enterprises in Nairobi for further processing.

Depending on the type of plastic, the difference between the buying price forraw materials and the selling price for the plastic chippings produced is 300-500% (i.e. EUR 0.075 per kg of material becomes ca. EUR 0.35's worth ofproduct). Although precise cost calculation remains a managerial problem, theproject can survive well with this profit margin. Difficulties are mainly causedby fluctuating prices for the products, which are sometimes changed at will bythe predominantly Indian wholesale buyers and enterprises that furtherprocess the material.

As a next step, the project plans to purchase an agglomerator in order toprocess foil waste as well.

needed. Often foil waste must bewashed manually, and locally madewashing drums can facilitate this task.

Sorting of plastic waste in Kisumu, Kenya/59/

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Assessment of Costs

Simple plastic recycling equipmentand machines produced in manyindustrialising countries (such asIndia, China, Brazil, etc.) areconsiderable less expensive as thosemade in the industrialised countries ofEurope, North America or the FarEast. Their comparatively lowerprocessing capacities and simpleoperations make them potentiallywell-suited for use in urban poorsettlements.

As a rough guide, shredder mills areavailable at prices starting from USD3,000, pot agglomerators from USD5,000, and granulation equipmentfrom USD 15,000.

Main FeaturesRecycling of plastic components from household waste to produce marketableintermediate products (hard plastic chippings, foil agglomerate, granulate) withappropriate technology

ApplicationWhen a market for recycled plastics exists and appropriate small-scaletechnology is accessible

CostsFor small-scale industrial operations: shredder mills, available at prices startingfrom USD 3,000, pot agglomerators from USD 5,000, and granulation equipmentfrom USD 15,000.

OperationsSmall-scale industrial level operations, suitable for self-help initiatives and smallenterprises

InterfacesPossible marketing for further processing in the formal sector outside thesettlement

AdvantagesProduction of marketable goods from waste with relatively low equipment andmachinery requirements; creates income and jobs at small-scale industrial level;environmentally friendly

DisadvantagesRequires a lot of cleaning to achieve acceptable product quality; basicknowledge of materials and machines needed for sorting and processing;production of agglomerate is energy-intensive

To be ConsideredProcessing capacities of machines should correspond to amounts of materialthat can be collected for recycling

Mobile press for scrap drink cans/61/

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Application

In urban poor settlements, manypotentially recyclable metal items (e.g.non-ferrous metals, cast iron parts, orbulky steel objects) are rarelydisposed of in household waste. Therecycling of metal is thereforegenerally of less relevance here thanthe recycling of paper or plastics.Metals that are thrown away mainlyconsist of beverage or food cans,defunct small appliances with metalcomponents, or cooking utensils. Inmost cases, these are thin pieces ofiron, steel or tinplate, of low qualityand little value.

In general, the only items thatpromise worthwhile recyclingrevenues are aluminium drink cans.However, globally only 50% of drinkcans are made from aluminium, whilethe other 50% is made from tinplateof significantly less value. Moreover,due to their high material value,aluminium cans are specially soughtout by all kinds of waste collectorsand recyclers, and rarely end up inhousehold waste.

Against this background, only twotechnical solutions are relevant formetal recycling at settlement level,and these are presented in moredetail in this section. They are:• the sorting and compacting of

scrap metal as a basis for furtherprocessing;

• the recycling of aluminium drinkcans.

Dimensioning and Operations

Baling presses should be selected sothat they have enough pressure toproduce stable and solid bales. Forsmall-scale processing on the spot(see figure 61), bale sizes should bemovable and transportable withoutlifting gear.

Metal separation from householdwaste presents no major technicalchallenges or requirements. However,to achieve a good price, it will beimportant not to mix non-ferrousmetals, e.g. copper, brass or tin, withscrap iron.


Scrap metals commonly found inurban poor settlements are hardlyever recyclable in a profitable andefficient way. Moreover, to do so canrequire further processing in electricalsteel mills, which do not exist in alldeveloping countries. In addition,large transport distances that may beinvolved are usually not economicallyfeasible.

SORTING AND RECYCLING OF METAL

Technical Solutions

Sorting and compacting of metal:Metal can be separated manually fromhousehold waste relatively simply. Theuse of magnets can be an option toseparate iron parts from largervolumes of waste. If, for marketingpurposes, scrap metal has totransported over large distances,compacting with baling presses can beuseful.

Recycling of aluminium: As alu-minium cannot be extracted withmagnets, it is more effective toseparate it out at source (households,restaurants, hotels, etc.). Due to theirlow weight (13g) and bulk (1 ton =77,000 cans), aluminium drink cansmust be collected in large numbersand compacted by baling presses.Scrap from aluminium drink cans iswell-suited for processing into basicconsumer items in small localfoundries.

In many countries, collected cans arealso used directly to produce variousgoods (e.g. oil lamps, containers, rooftiles, toys, etc.). Cans are cut up, andthe pieces assembled and soldered orriveted to make the intended item.

Oil lamps manufactured from cans inCotonou, Benin /60/

Collection of drink cans/62/

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The collection of scrap iron, althoughnot necessarily from household waste,is traditionally a preferred activity ofinformal, small-scale industrialrecycling enterprises, and basicallywell-suited for self-help initiatives.Due to the small volume of metal inhousehold waste and its low value, itwill usually be of little interest orrelevance in urban poor settlements.

Molepolele, BotswanaCollection of drink cansA GTZ project to promote local refusemanagement and recycling supporteda local small entrepreneur in thepurchase of a mobile baling pressintended to improve the collection oftinplate drink cans. The entrepreneurwas not able to provide any capital orcollateral, but it was possible toobtain a loan from a governmentalfund for the promotion of small-scaleindustries. It was, however, necessaryto convince the lending institutionthat recycling was a productiveactivity that could be financed withinthe fund's guidelines.

The entrepreneur collects and buysdrink cans, presses them into balesand sells them to intermediatetraders. The scrap produced is thenbought by a private sector agency(Collect-A-Can) that is financed by theSouth African steel and beveragecanning industry, and is melted andfurther processed in South Africansteel mills.

Using the equipment as collateral, heis now able to get further loans.

Assessment of Costs

To collect and market large amountsof drink cans, a small baling press thatcan be purchased for about USD10,000 will be needed.

Costs for larger presses that canprocess large heavy items, can rangefrom USD 100.000 to 1 million, andcan therefore not be financed by smallenterprises or self-help initiatives.However, compact iron and steelscrap can possibly be marketed inbulk.

Main FeaturesSeparation, sorting and possibly further processing of metal components ofhousehold waste, mainly of non-ferrous metals (e.g. aluminium drink cans);production of goods and consumer items (e.g. oil lamps) from tin cans

ApplicationWhere a market for scrap metal exists and appropriate small-scale technology isaccessible

CostsSmall baling presses for lightweight scrap can be purchased at prices startingfrom USD 10,000.

Operationspossible at small-scale industrial level, suitable for self-help initiatives and smallenterprises

InterfacesPossible marketing for further processing in the formal sector outside thesettlement

AdvantagesProduction of marketable goods from waste with relatively low equipment andmachinery requirements; creates income and jobs at small-scale industrial level;environmentally friendly

DisadvantagesOnly aluminium drink cans are of substantial value; long transport distances formarketing scrap metal are not economically feasible; large-scale processingcapacities (electrical steel mills) required

To be ConsideredSeparation of iron and non-ferrous scrap components is important formarketing.

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Application

Glass recycling is of limitedimportance in urban poor settlementsbecause reusable intact glass bottlesand containers are generally soldrather than thrown away as waste.

Usually only broken glass will befound in household waste in poorresidential areas, and this is difficult tocommercialise.

There will therefore be only two mainoptions for glass recycling atsettlement level:• sorting and conditioning of scrap

glass with the intention of sellingit to glassworks outside thesettlement;

• processing in small localmanufactories, where hand-blownglass goods are produced.

Technical Solutions

Sorting and conditioning: Largerglass pieces and shards are manuallyseparated from waste; smaller piecesare discarded.

Broken glass or deliberately brokenglass bottles or containers are sortedby colour and packaged for transportto glassworks.

Processing in local manufactories:In this form of recycling, scrap glass isprocessed in small local glassworksinto consumer or craft items.

Dimensioning andOperations

Sorting and conditioning: Thecollection and conditioning of glass isusually a small-scale industrial activityin which glass is sorted according tocolours and possibly broken intopieces of similar size. It does notrequire any investments in machines,but only needs protective clothing,like gloves, shoes and safety goggles,and some basic tools, like hammersfor breaking glass into smaller pieces,or shovels for loading. Sorting shouldbe done on a concrete or asphaltedsurface, and appropriate transportcontainers should be made available.

When sorting and breaking glass,protective clothes should be used toavoid injuries to hands, feet and eyes.The sorting area should be walled orfenced to prevent the entry ofunauthorised persons, especiallychildren.

Careful separation by colours will beimportant for later marketing. Evensmall amounts of mixed colouredglass can seriously hamper marketingchances; white glass in particular,should be free of other coloured glasspieces. The presence of certainamounts of paper residuals, plastic ormetal lids or tops is uncritical, as theywill be separated mechanically at theglassworks or be burnt in glassfurnaces. On the other hand, it isimportant that stones and gravel, andin particular earthenware shards, arenot mixed with the glass.

Processing in local manufactories:This requires a melting furnace thatcan be heated up to temperatures of1,200 - 1,400°C. Depending on thekind of processing, other equipment,such as hand-blowing forms, and

SORTING AND RECYCLING OF GLASS

Production of hand-blown glass frommelted glass scrap in La Paz, Bolivia /63/

cutting and grinding tools, will beneeded. Moreover, a reheatingfurnace may be necessary to heat treatthe glass in a final processing step.The broad use of this technology inurban poor settlements will, however,be difficult because of the investment,knowledge and technical skillsrequired.


The use of broken glass as rawmaterial for the production of newglass items is a well-established andtraditional technology. However, dueto economies of scale, most glassrecycling is done nowadays throughlarge-scale industrial processes.

The availability of glassworks not toofar away from a settlement will thus bethe most relevant factor for possibleglass recycling activities. In mostcases, it will not be economicallyfeasible to transport broken glassscrap over large distances, e.g. toneighbouring countries.

Production of beads from glass waste inNairobi, Kenya /64/

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Nairobi, KenyaGlass recycling at settle-ment level

The Imani Glass Recycling Project isan initiative in one of the oldest slumareas of Nairobi, close to the MathareValley. In the context of a Churchsupported development project, asmall workshop was established forthe processing of scrap glass. Themajority of workers are women, whomanufacture beads, which are usedto make craft objects, from brokencoloured glass scrap. A gas-operatedmelting furnace was purchased, inwhich broken glass is melted indifferent ceramic moulds for differentcolours. Beads are made individuallyand by hand: a small amount ofmelted glass is put on the end of aniron stick, and then formed into abead by turning the stick whileapplying some other smallsupplementary tools. When it hascooled down, the iron stick separatesfrom the glass and leaves a hole inthe bead. Beads are produced indifferent colours and sizes, and aresold to craft workers for furtherprocessing.

The experience gained frominstalling and setting up the meltingfurnace enabled the project workersto construct a second furnacethemselves. The production of hand-blown glass items is planned as thenext step. Sometimes there areproblems because of the high costsof gas bottles for operating thefurnaces. The group is thereforelooking for options to replaceexpensive gas by other cheaper fuel.


Glass, in particular intact bottles andcontainers, has always been separatedfrom refuse and recycled. Extendingthis to the collection of broken glass istherefore a logical next step. Glassrecycling would be further facilitated ifglass waste was picked-up and sortedby recyclers directly at the placeswhere it is mainly generated, e.g. bars,restaurants, hotels, etc. Environmentalgroups and self-help initiatives canpossibly support such an approachthrough appropriate information andawareness campaigns.

Assessment of Costs

Sorting and conditioning scrap glassfor selling to glassworks requires littleinvestment. Basically, all the work canbe done manually, so recurring costswill mainly consist of wages. If glasswaste is to be picked-up from where itis generated, suitable vehicles will beneeded, which can entail associatedadditional operational costs.

Main FeaturesSeparation, sorting by colour andpossibly further processing of glasscomponents of household waste

ApplicationWhere a market for recycledproducts exists and appropriatesmall-scale technology is accessible

CostsApart from some containers andprotective clothing, no otherinvestments are needed, so long asrecycling activities are limited tosorting and conditioning

OperationsPossible at small-scale industrial level;suitable for self-help initiatives andsmall enterprises

InterfacesWhen marketing and furtherprocessing takes place in the formalsector outside the settlement

AdvantagesProduction of marketable goods fromwaste with relatively low equipmentand machinery requirements; createsincome and jobs at small-scaleindustrial level; environmentallyfriendly

DisadvantagesDue to the relatively high specificweight of glass, transport costs forcollection and marketing are high;further processing usually requireslarge-scale industrial capacities

To be ConsideredCareful separation of glass by colouris necessary to improve marketingchances

Schematic sketch of a simple trench landfill /65/

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• not in geologically unstableregions;

• not in ecologically sensitive orhistorically important areas;

• not near settlement watercatchment areas or wells;

• not in regions with high groundwater levels or springs;

• not in regions with permeable soil;• not in rocky regions with

insufficient soil cover;• not closer than 500m meters to

inhabited areas;• not in the main wind directions of

settlements;• not in areas crossed by

infrastructure mains (water, gasund electricity).


REFUSE DISPOSAL AND DEPOSITING

SMALL-SCALE LANDFILLS

Application

In most urban poor settlements, thefinal disposal of refuse will only bepossible outside their boundaries. Thiswill generally require connecting refusecollection at settlement level to city-wide refuse disposal systems with acentral landfill .

Where connection or access to a centrallandfill site is not possible or feasible,e.g. in isolated settlements far outsidethe main built-up urban area, or in anurban quarter that is difficult to access,an alternative can be to establish thesettlement's or part of the settlement'sown small refuse dumping site.

To save costs and reduce the effort ofsite development, operation and follow-up care, such small dumping sitesshould only be used for residual waste,i.e. waste from which valuable andrecyclable material has been extracted.This, however, presupposes that thereis a functioning solid waste manage-ment and recycling system at local level,which can be a major challenge inmost urban poor settlements.

Dimensioning

The most appropriate kind of smallrefuse dump at settlement level is atrench landfill. For this, trenches witha width of 2-3 m and a depth of 2mneed to be dug. They should be builtwith a slope to one side to drainrainwater. Ideally they should be builton a site that has a natural slope. Inthese cases, trenches should be dugfrom below to above to avoid wateraccumulating in the trench duringexcavation. The excavated earthshould be piled alongside the trench,to be used later to cover the refuse.The sidewalls should be slanted,instead of vertical, to preventcollapsing.

The follow exclusion criteria shouldbe applied in the selection of possiblesites for small local landfills:• at least 1 km distance from

airports;• not below the highest flood levels

of the previous 50 years; • not closer than 50m to surface

waters (lakes, rivers etc.);

Simple trench landfill in Aqaba, Jordan/66/

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Operations

Depositing of refuse should start atthe higher end of the trench to ensurethat the landfill is not filled with water.In order to work systematically, refuseshould be tipped in one place at atime. Deposited refuse should becovered with previously excavatedearth every day or, if that is notpossible, at least once a week. In thatway, a layer of earth can be graduallybuilt up covering the trench. Becausethe landfill will sink, possiblyunevenly, over time, this avoids thedevelopment of gullies, which mayaccumulate water, or cracks that maygo through to the buried refuse.

It will be useful to fence the landfillsite to prevent paper or plastic wasteblowing away, and to restrict theaccess of unauthorised people. Inaddition, this enables control on thetype of refuse to be deposited byentering vehicles.


The simple construction of a trenchlandfill does little to prevent theseepage of pollutants into the soil andgroundwater. It will therefore beimportant that only household refuse,and no industrial or hazardous wasteis deposited. Sites should be carefullyselected to especially avoid negativeimpacts on groundwater resources.Waste should be sorted to reduce itsorganic content in order to avoid bio-chemical processes, which cangenerate seeping water and gas.


Due to their simple set-up and lowoperational requirements, trenchlandfills can be operated by self-helpgroups at community level.Operational costs can be covered by acombination of user charges for localrefuse collection and possiblerevenues from the sorting andrecycling of valuable wastecomponents.

Assessment of Costs

The costs of trench landfills willinvolve initial investments (possiblyfor purchasing the necessary land, andthen for fencing, buying a frontloader, etc.), and operating expenses(fuel, maintenance, wages).

In most cases, costs will have to becovered by residents when no supportis available from public or govern-mental institutions.

Main FeaturesDisposal of residual waste afterseparating out and recycling valuablefractions; depositing of waste in earthtrenches subsequently covered withearth

ApplicationOutside built-up areas on sites wheregroundwater resources will not beaffected

CostsInvestment and operating costs aremainly defined by the size of thelandfill

OperationsCan be operated by self-helpinitiatives at community level

InterfacesWith increasing landfill size andwaste volume deposited, highercosts, higher operationalrequirements and more need forcontrol and supervision becomesnecessary. This may call foroperations to be taken over bymunicipal services.

AdvantagesSimple and inexpensive wastedisposal that can be done by self-helpinitiatives when disposal at a centrallandfill site is not possible

DisadvantagesNo protection against seepage ofpollutants into soil and groundwater;no provision for disposal of industrialand hazardous waste

To be ConsideredControl over refuse before it isdeposited .

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DISPOSAL OF HAZARDOUS WASTE

Application

Hazardous waste can often be foundin household or commercial waste inurban poor settlements. The mostcommon types of hazardous materialare batteries, as many households areonly connected to unreliable orinformal (i.e. illegal) electricitysupplies, if at all, and thus largelydepend on batteries for all kinds ofappliances.

In quarters with larger numbers ofcommercial enterprises, otherhazardous forms of waste, such asscrap tyres, used oil, solvents, paintresiduals, acids or lye (strong chemicalwashing solutions), may be found.Small restaurants or food stalls maythrow used cooking fats away. Healthstations and doctors' practices aresources of medical waste infected withbacteria.

Moreover, informal recyclingworkshops and activities can producesignificant amounts of highly pollutedwastewater, ashes and cinder, andmetal or non-metallic residuals.

There are no standardised proceduresfor disposing of these highlydangerous materials. Different kindsof substances will therefore needspecialised treatment, according totheir characteristics and pollutantcontent.

Returning problematic material to itsproducer, or handing it over tospecialised enterprises for treatment,as practiced in most industrialisedcountries, is uncommon in mostdeveloping countries, and is seldom arealistic option, particularly in urbanpoor settlements. At settlement level,it will thus generally only be possible

protective clothing.• Used batteries, capacitors, soluble

salts with heavy metalcomponents, soluble cinder,injection needles and used glassphials can be put into plastic ormetal containers and then sealedwith concrete or asphalt. Finaldisposal at a normal landfill site orin a secure refuse pit is thenpossible.

• Paint residuals and small amountsof solvent can be dried by normalevaporation, and then disposed ofwith other solid waste, ordeposited in a secure refuse pitinside the settlement.

• Acids and lye can possibly beneutralised with appropriatechemical additives. If they do notcontain any heavy metals, they canthen be diluted with otherwastewater and discharged intothe sewage system (if there isone).

• Heavy metal salts in solvents canbe concentrated by evaporation orvaporisation. The residual salt canbe sealed with concrete or asphaltas described above, and thendisposed of.

Dimensioning andOperations

Pits for hazardous waste, in particularfor infectious medical waste, shouldbe designed so that they can take insufficient amounts of waste oversuitably long periods of time, and, ifnecessary, allow for the possibility oflater final sustainable disposal.

to try and reduce the hazards result-ing from such waste components, andto look for ways of disposal thatminimise risks to the natural environ-ment and human health. Thefollowing basic options are possible:• separate collection and disposal of

hazardous materials;• depending on the particular risks

of different materials, measures totransform pollutants into lesshazardous waste, or to seal themto avoid or limit their dissipationinto the environment;

• if there are no possibilities oftransport to safe disposal sites orfacilities outside the settlement,the construction of speciallyprotected waste pits for temporaryor permanent disposal.

Technical Solutions

When no other, more environment-friendly options are possible, differentminimum solutions that can possiblybe applied for most commonhazardous waste components, are asfollows:• Waste oil, non-halogenated

solvents, fats and medical refusecan be incinerated in specialfurnaces when no other means ofsafe disposal are available. It willbe important to ensure that thereare high enough temperatures andadequate conditions for oxidationinside the furnace. Moreover,furnaces should have sufficientlyhigh smokestacks, with the mainwind direction leading away fromthe settlement. Operating staffshould be provided with

Schematic sketch for the construction ofa secure refuse pit /67/

63



The pit chamber will need to becovered by a lid, a removable plate ortop section, with a ventilation pipe.The lid should be lockable to preventunauthorised opening, particularly bychildren. The ventilation pipe will notbe necessary in all cases. In hotclimates, where organic wastecomponents decompose quickly, itwill be sensible to consider ways ofavoiding smells when opening the lidfor waste disposal e.g. by wrappinglikely material before depositing it.

Sites for the digging of secure refusepits should be selected according tothe same criteria as for pit latrines*.Soluble waste components that do notorganically decompose easily or at all(such as heavy metal salts, solvents,mineral oil, etc.), should not bedeposited unsealed in such refuse pits.

u *for criteria for the constructionof latrines, see chapter 3


It will not be possible to dispose of allhazardous waste residuals in anenvironment-friendly way atsettlement level. For each particularmaterial, appropriate solutions willhave to be found. This presupposesspecial technical knowledge, which isoften not available in urban poorsettlements. Moreover, the risksresulting from hazardous waste areoften unknown to the residents.


If individual community membershave the necessary technicalknowledge and skills to distinguishand treat hazardous waste, most ofthe settlement internal solutionsdescribed above can be applied in self-help initiatives with relatively littleeffort and at reasonable costs.However, such initiatives will have tobe complemented by informationcampaigns to raise residents'awareness of the risks of hazardouswaste and its handling.

Self-help initiatives can also establishand operate special collection pointsfor hazardous waste to be transportedfor disposal outside the settlement.

Assessment of Costs

All the measures and solutionsdescribed above can be implementedwith limited financial resources. Themain effort will have to focus on theestablishment of appropriatesettlement-wide logistics for collectionand disposal.

Main FeaturesIdentification and separate collectionand disposal of hazardous waste,such as used batteries, oil and fat,solvents and paint residuals, acidsand lye, small-scale industrial refuseand medical waste

ApplicationUrban poor settlements with fewother alternatives for the collectionand treatment of hazardous waste

CostsLow: measures use simple technicalsolutions

OperationsCan be operated by self-helpinitiatives at community level

InterfacesIf possible, hazardous wastecomponents should be handed-overto municipal or authorised privatesector waste enterprises forspecialised treatment and disposal

AdvantagesBetter organised disposal and healthhazard awareness campaigns helpprotect local residents from healthrisks

DisadvantagesLack of specialised know-how andinformation; insufficient wastemanagement structures

To be ConsideredHazardous waste should not bemixed with other waste, butseparated and treated individuallyaccording to characteristics ofspecific materials

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WASTEWATER3

66

3.1 WASTEWATER

PROBLEMS AND CHALLENGES

Problems

Most urban poor settlements havedeveloped in an unplanned waywithout following formal urban layoutstandards. High densities and oftenextremely narrow internal streetsmake it difficult to establish a sewer-age system. Municipal infrastructure,eg. for wastewater treatment plants, isusually completely lacking.

Without functioning municipalsanitation systems, problems ofdischarging wastewater from kitchens,bathrooms and toilets have to besolved individually. Where there issufficient space, it may be possible toconstruct a simple filtration pit forgreywater and a latrine.

However, in densely built metropo-litan areas, e.g. at the fringes of Indianmegacities, there often is no space.The few public open spaces that mayexist (e.g. railway tracks) are thus usedfor defecation, and greywater fromkitchens and bathrooms is simplydischarged onto streets.

In industrialised countries with amplewater supplies, the usual sanitationmethod is water-borne sewerage (so-called flush-and-discharge-systems).

Factors impeding efficientsanitation in urban poorsettlements:

• The usually unplannedpattern of settlement develop-ment renders it difficult toconstruct efficient sewage sys-tems.

• High densities and limitedspace hamper ex-postimprovements of sanitationinfrastructure.

• Municipalities that do notsupport the connection ofpoor areas to existing sewagesystems.

• Sanitation is often left to theindividual initiative of resi-dents.

• Functioning self-helpsanitation systems requirejoint communal efforts withsome degree of participationand a sense of ownership.

Large amounts of fresh water flushrelatively small volumes of wastewaterand faeces through piped systems tocentral treatment plants.

This conventional form of sewerageused in industrialised countries, andwhich is also often applied inwealthier urban neighbourhoods indeveloping countries, is, however,hardly appropriate for urban poorsettlements.

Globally, about 80 countries, withabout 40% of the world's total po-pulation, are affected by regularperiods of water shortages. 95% of allwastewater generated in Third Worldcountries is discharged completelyuntreated into surface waters. Manycities do not have any wastewatertreatment system, and even in citiesthat do have sewage systems, only afew households are actually connectedto it.

Where there is a lack of treatmentcapacities, the mixture of differenttypes of wastewater can seriouslyaggravate hygiene problems, as smallamounts of hazardous wastewater(e.g. faeces) can pollute large volumes

Discharging of wastewater and refuse in canals in Thailand/68/

Discharging wastewater in a floodedseashore area /69/

of less problematic wastewater (i.e.rainwater, surface water and greywater from kitchens and bathrooms).

67

3.1 WASTEWATER


Potentials

Suitable sanitation options for urbanpoor settlements are simple water-saving on-site and off-site systems.Such systems are characterised by:• low investment requirements;• low water consumption with low

(regular) pipe flushingrequirements;

• adequate environmental healthand hygiene standards;

• possibilities for self-helpconstruction and operation;

• feasibility of connection tocitywide municipal sewagesystems.

Community-operated wastewatersystems call for high levels ofparticipation and resident self-help,but this cannot always be mobilised.

Availability of water as adecisive factor for waste-water systems

The availability of water, or rather itsscarcity, is a decisive factor in selectinga sanitation technology.

Water supply is often not sufficient,therefore solutions at household levelor decentralised dry or semi-dry (on-site) systems will be needed. Insteadof systems providing continuousflushing of wastewater and faecesthrough interconnected pipe work, asin conventional sewerage,discontinuous sanitation options atsettlement level will usually bepreferable.

Approaches

The basic principle for the design andselection of sanitation options forurban poor settlements shouldtherefore be:

Limiting and avoiding themixing of wastewater andfaeces (don't mix!)

As far as possible, mixing the followingwastewater components should beavoided:• urine and faeces;• faeces and water;• greywater and sewage• wastewater and rainwater; • household and industrial

wastewater.

Separating urine and faeces canreduce or even eliminate problemssuch as bad smells or the breeding offlies, and storage, treatment andtransport can be facilitated. Separatingfaeces from toilet flush-water alsogreatly reduces the treatment neededfor relatively small volumes of urineand faeces.

Storage systems and local treatmenttechnologies needed for suchseparation will have to comply withthe following requirements:• secure storage that protects both

the environment and theinhabitants;

• the facilitation of aerobic oranaerobic decompositionprocesses;

• the conditioning of wastewater,e.g. the separation of solid andliquid components, of grease etc.;

• easy access for transport anddischarge.

Where the construction of pipedsystems (off-site systems) is possible,“unconventional” systems, known assettled sewage, simplified sewage orcondominial sewage, might offer themost appropriate solutions. They caneither be connected to decentralisedsmall treatment plants or to the city-wide sewage network.

Sanitation systems in urban poor areaswill usually require a high level ofparticipation and self-help.

Shallowly laid sewage pipes with small diameters in Karachi, Pakistan/70/ /71/

68

3.1 WASTEWATER


Since more developed sanitationsystems are communal installationsthat cannot be constructed oroperated individually, they will usuallyrequire a communal approach. Forthis purpose, functioning communityorganisations will be necessary to takeon the construction and operation ofwastewater systems.

In most cases, it will be difficult togenerate direct operating revenue forsuch approaches. Financialcontributions from individualhouseholds will thus have to beorganised and monitored.

Many sanitation services at settlement level can beprivatised

Many services necessary to construct and operate communal sanitation systemsat settlement level can be contracted to small private enterprises, either forindividual works or services, or as more comprehensive packages. These mayconsist of the following:• construction and maintenance of piped sewage systems;• emptying of septic tanks and latrines;• operation of small decentralised wastewater treatment plants;• composting of sludge derived from organic waste generated by refuse

separation;• operation of biogas installations.

Such services will have to be paid for directly by individual users either accordingto their utilisation of the particular service, or, in the case of communalinstallations, by paying a fixed share of the service's costs. Composting and biogasinstallations can possibly cover part of their costs through the marketing of thecompost, biogas or energy produced. The opportunities for jobs and income thatthis might offer may improve residents' acceptance of such solutions.

Self-help laying sewage pipes in Aswan, Egypt/72/

Emptying of septic tanks by privatesmall-scale enterprises /73/

69

3.1 WASTEWATER


The diagram below is an overview of sanitation options and processes. This publication mainly focuses on sanitation optionsat settlement level with a view to the specific problems and conditions in urban poor settlements: city-wide systems andoptions are only dealt with so far as they are relevant to interfaces with local solutions. /74/

70

3.2 WASTEWATER

WASTEWATER GENERATION

Basic Concepts

The generation of wastewater isdirectly related to the water supplyprovided. Usually, the larger thewater supply, the more thewastewater generated. However, inmost urban poor areas, water supplyis scarce. Large parts of the populationhave only limited access to potablepiped water. They get their watereither from public faucets or wells, orbuy it from private water vendors. Fewhouseholds have their own private tapor water connection on their plot.Even for those, water is often rationedor not permanently available.

Wastewater can be classified accordingto its components and concentrations: • surface water: rainwater

discharged into wastewatersystems;

• greywater: wastewater fromkitchens and bathrooms;

• sewage or black water:wastewater from toilets;

• industrial wastewater:hazardous effluent fromcommerce and industry.

Depending on its components, theneeds for cleaning and treating thedifferent types of wastewater can varyconsiderably. Treatment costs can bereduced significantly when lesspolluted wastewater can be reused forother purposes (e.g. use of rainwateror surface water for toilet flushing).

It is generally difficult to reliablyestablish the amounts of wastewatergenerated. In most cases, wastewateris not metered.

A rough indication of wastewatervolumes may be derived from waterconsumption, which is largelydetermined by the economicconditions and life styles of a countryor a region.

Furthermore, it has to be borne inmind that in some countries rainwater

Economic situation /conditions water consumption at household level

High to medium income 200 l/capita and day(Europe/USA, warm climate: connected to public water supply)

High to medium income 165 l/capita and day(Europe: connected to public water supply)

Low income(Europe: connected to public water supply)• small appartment with shower 100 l/capita and day

Low income(low income: public faucet)• urban 70 l/capita and day• rural (incl. laundry) 65 l/capita and day• rural (only drinking water and personal hygiene) 25 l/capita and day

is discharged into sewerage systems.Wastewater generation may thus alsodepend on the volume and seasonaldistribution of rainfall.

Insufficient water supply results in the generation of only small amounts of wastewater:Discharging household wastewater at a central collection point in Cairo /75/

Procedures and Approaches

71

In addition to the absolute volume ofwastewater generated, its hazardouscomponents (e.g.. BOD5 and CODlevels*, sediments, etc.) will have to beconsidered. Of particular importance inthis context is that human faeces indeveloping countries have a greatermass because of their higher fibrecontent, and hence more solidcomponents will be discharged intowastewater. This will have to be con-sidered in determining the needs forflushing water and in dimensioning on-site sanitation facilities, such as latrines,compost toilets, septic tanks andbiogas installations.

An analysis of specific indicator bacteriacan be used to assess the hygienicqualities of wastewater and sludge, andits further treatment or possible use,above all for agricultural purposes.Among the bacteria found in faeces,Escherischia Coli, measured by numberper 100 ml, is an important indicator,as is the number of Helminth eggs perlitre of wastewater or sludge.

* BOD5 - biochemical (or biological) oxygendemand over 5 days; COD - chemical oxygendemand. Comparative tables on fibre content,BOD5 levels and bacteria occurring in stoolscan be found in the annex, together withquality guidelines.

3.2 WASTEWATER

WASTEWATER GENERATION

Factors Determining Volume and Type of Wastewater

Users/use water consumption

individuals 15 to 20 l per capita and day

schools 15 to 30 l per student and day

hospitals (with laundry) 220 to 300 l per bed and day

decentralised ambulant patient: 5 l per capita and dayhealth posts stationary patient: 40 to 60 l

per capita and day

mosques 25 to 40 l per capita and day

pour-flush latrines 1 to 2 l/flush

20 to 30 l/latrine and day

dry latrines 2 l/latrine and day(for cleaning)

Determining factors

• type of water supply provision

• sanitation facilities at household level

• wastewater system

• public infrastructure (community facilities, schools, hospitals,

mosques, commercial enterprises, etc.)

• life style and nutrition pattern

• cultural and religious specifics

• financial resources

A common problem: Mixing of wastewater and refuse /76/ Open sewage canal /77/

72

Schematic sketch: pit latrine /78/ Schematic sketch: VIP-latrine /79/ Schematic sketch: pour-flush-latrine /80/

3.3 WASTEWATER

WASTEWATER DISCHARGING AND TREATMENT

VIP-latrines: The VentilatedImproved Pit latrine is a furtherdevelopment of the pit latrine.

Inclusion of a simple ventilation pipesignificantly reduces bad smells andnuisance from flies, and thusconsiderably improves this simpleform of toilet's hygienic conditions.

Pour-Flush-Latrines: The pour-flush-latrine requires small amounts ofwater (2-3litres per flush) to dischargefaeces and to clean the toilet. Aresidual water seal reduces smellnuisances.

Pit-Latrines: This basic type of latrineis one of the simplest and most cost-efficient methods of dischargingfaeces. When a pit latrine is welldesigned and constructed, and isproperly positioned, it can significant-ly prevent infections caused by faeces.They can be operated without anywater.

SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE-SYSTEMS): LATRINES

Application

Latrines are one of the oldest and best-proven technical solutions for dealing with human excrement. Due to their excellentability to manage human faeces without the need for a water connection, they are the simplest way to dispose of faeces inmany urban poor settlements, and can be installed either as individual toilets or communal toilets. They are especially usefulin areas without functioning water supplies or other sanitation options.

A large variety of solutions and latrine types have been developed for different location-specific conditions and climates.Three of the most common and appropriate forms of latrines are:

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Simple pit latrine /81/

Minimum distance of latrines to different installations

3.3 WASTEWATER


Construction

The design and construction oflatrines will have to take into con-sideration the following aspects:• The latrine should be placed

downhill from, and at least 30 mbelow wells or other water sour-ces. The flow direction of ground-water streams should be takeninto consideration. For convenien-ce of use, the latrine should belocated not closer than 5 m andnot farther than 50 m from thebuilding or dwelling.

• When a concrete platform is used,it should extend at least 15 cmbeyond each side of the pit.

• Platform construction and anchor-ing over the pit: Where soil con-ditions are unstable (e.g. sand),foundations will have to beconstructed to stabilise the pitwalls before the platform is laid.

• Building materials, such as stone,wood or mud can be used toconstruct the latrine hut. Wherepossible, locally available materialsshould be used. The latrine hutshould have a door or apermanently screened offentrance.

• The roof should be slopedtowards the back of the latrine.

Some special considerations will beneeded in the construction of VIP-Latrines:• The ventilation pipe of a VIP

latrine should be placed so that ithas maximum exposure to the sunand it should be painted black (bywarming the pipe, the air within itwill be heated and rise; thepressure of the air in the pit willdrop, and it will be sucked intothe pipe, resulting in betterventilation of the latrine). Toallow for adequate ventilation, thepipe should have a diameter of atleast 15 cm and should project atleast 50 cm over the latrine roof.

• The pipe's opening should becovered by corrosion proof fly net(mesh size smaller than 1,3 mm)to prevent insects entering.

• To ensure continuous ventilation,the lid over the defecation holeshould not be airtight.

• The latrine's interior should bedarkened to reduce the number offlies and insects attracted to thepit by light.

Type of installation distance [m]

Residential dwellings 6

Hospitals, food stores, etc. 10

Wells or other sources of water supply 15-30

For latrines on sandy soil with high filtration capacity, the minimum distances to sources of water supply will have to be applied.

Dimensioning

To determine the pit size requiredand to calculate the latrine's possiblelife span, the following formula can beused:

V = n * s * L

V = aeffective pit volume [m3]n = number of userss = solid feces volume [m3]L = life span [years]

The volume of solid faeces generatedper year is calculated at 0.04 m3 perperson. For a user group of 25(recommended maximum number ofusers per latrine), a pit with a volumeof at least 0.04 x 25 = 1m3 per yearwill therefore be needed. To calculatethe effective pit volume correctly, anair space of at least 0.3 m will have tobe added. When the pit volume isknown or estimated, the equation canbe reformulated to calculate thelatrine's life span, L (i.e. L= V/ n*s).

74


Digging a hole, e.g. for a well or formining, is a common skill in mostsocieties. Normally therefore, it willnot be difficult to find workers for thisin urban poor settlements.

Locally available materials andcommon and/or traditional techniques(wood construction, thatched or stonewalls, etc.) can be used to build latrinehuts. Such techniques will probably besimilar to those used to construct the(often self-built) houses in the area, solatrines can usually be built throughself-help initiatives. Some assistancemay be needed to select appropriatelocations for latrines. In many cases,this may be provided by localenvironmentally involved NGOs.

Assessment of Costs

Apart from manual labour, theconstruction of a latrine will requirethe following tools and materials: • spades and pickaxes;• a squatting platform made out of

concrete (or similar material);• a lid for the defecation opening

(wood, metal or cement); • locally available materials for the

latrine hut and the door.

Most of these tools and materials willusually be available locally at lowcosts.

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): LATRINES


Latrines should not be built in flatareas or depressions affected byseasonally high groundwater levels orflooding. Otherwise, pits could fillwith water and become ideal breedingareas for mosquitoes and otherinsects. An overflowing pit containingexcrement would contaminate theenvironment and cause health hazardsand infections.

Constructing latrines will be difficult inareas with rocky soil or highgroundwater levels. Necessary designadjustments, e.g. to turn it into anaqua privy, are costly and will have tobe considered in an early planningstage.

The construction of latrines is not initself enough to reduce the risk ofinfections from excrement. To do thiseffectively, they must be regularlycleaned and maintained. As a rule,private latrines are normally keptcleaner and are better maintainedthan public facilities.

If the excrement sludge is to be usedwithout any further treatment asfertiliser in agriculture or horticulture,it will have to be stored for at leastone year after the latrine has beenclosed in order to reduce itspathogenic effects on humans to aminimum.

Latrines are not a viable sanitationoptions in areas with residentialdensities above 300 persons/ha, as thenecessary minimum distances tobuildings or wells cannot be assured.


The following rules should be takeninto consideration in operating andmaintaining latrines:• The pits of pit latrines should be

covered to avoid smell nuisancesand insects inside latrine huts andin their direct surroundings.

• The pit's squatting platform and itssurroundings should be cleanedon a daily basis.

• Latrines should be provided withsome form of lighting for nightuse. Facilities for washing handsafter use should also be provided.

• To avoid contamination andhealth hazards, the latrine shouldbe closed, when the pit is filled upto 0,5 m below the platform.

• So that small children can uselatrines safely, i.e. so that theycannot fall into the pit, defecationopenings should not be largerthan 18 cm in diameter.

Latrine huts built with locally available materials /82//83/

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3.3 WASTEWATER


Main FeaturesInexpensive and simple on-site sanitation option without the need for a watersupply; discharge and storage of faeces in a covered pit

ApplicationIn settlements with insufficient or irregular water supply provisions and withsuitable soil conditions

CostsLow, as most materials needed for construction are usually cheaply availablelocally

OperationsSelf-help construction, operations and maintenance is possible

InterfacesAs or when required, emptying of latrines and discharging of sludge carried outby city-wide service providers (e.g. municipalities, private sanitation enterprises)

AdvantagesSimple and cost-efficient system; can be constructed with local buildingmaterials; low need for technical skills and know-how

DisadvantagesRisk of flooding (including seasonal flooding) and environmental contaminationwhen located in low-lying land and/or depressions; inappropriate for areas withrocky subsoil or high groundwater levels

To be ConsideredSuccessful prevention of health hazards will largely depend on social andcultural traditions, and on regular cleaning and maintenance.

Jalalabad, Afghanistan Latrine construction in arefugee campThe Sar-Shahi Refugee Camp nearthe Afghani city of Jalalabad wasestablished in 1994/95 in the wake ofthe Afghan war. It housed up tohundred thousand refugees in in-tolerable hygienic conditions in avery confined area. The prefabri-cated communal toilet blocks in thecamp were totally overloaded by fastgrowing streams of refugees.Moreover, the refugees did not feelresponsible for cleaning or main-taining them.

As a result of this experience, adifferent approach was used when asecond camp was established in NewHadda. Here, support was given toindividual family groups in the self-help construction of improved pitlatrines. Within six months, basicsanitary facilities for about 90,000people were built. The latrines were:

• adapted to local conditions withthe use of local buildingmaterials and techniques (woodand clay construction);

• inexpensive due to the high levelof self-help;

• sufficient, in terms of numbers,to serve the refugee population;

• adequately maintained, as thefamily groups involved in theirconstruction developed a senseof ownership.

Where possible, only private sanitaryfacilities were built, which was morein line with the social and culturalcodes of the Islamic communitythere.

Double chamber dry or compost toilet/85/

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Schematic sketch: options for separating faeces and urine /84/

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): DRY AND COMPOST TOILETS – SEPARATION OF URINE

Construction

In dry toilets, faeces are separatedfrom urine, and their undesirableconstituents are neutralised by drying.In compost toilets, this is donethrough controlled aerobic decom-position processes.

Urine and stool can be separated indifferent ways: usually, separation “atsource”, i.e. before any mixing takesplace, will be the preferred solution.

Separating urine and stools cansignificantly reduce or even totallyeliminate problems such as smellnuisances or breeding flies, and canalso facilitate the storage, treatmentand transportation of faeces. Urineitself is comparatively germ free andcan be directly applied, untreated orin solution, as fertiliser. The solidcomponents of excrement can beeasily composted, and compost toiletstake advantage of this. Some types ofcompost toilets are constructed sothat other organic waste (e.g. fromkitchens) can also be disposed ofthere, which further facilitates thecomposting process.

Dry Toilets - PossibleApplications

Dry toilets and compost toilets thatprovide for the separation of urineand stools are an alternative solutionto simple latrines, which can be in-appropriate in areas with high resi-dential densities, risks to potablewater supplies or groundwater re-sources, or with difficult ground con-ditions (e.g. rocky subsoil). They canalso be a viable alternative to techni-cally and financially more complexsanitation solutions (e.g. septic tanksor conventional sewage systems).

Although the separation of urine andfaeces is a traditional solution in someparts of the world (e.g. in Yemenicities), in most regions, and in parti-cular in densely built-up urban areas,it is an innovative approach, and thereis only limited practical experiencewith it to date.

Dry toilets avoid potential groundwatercontamination and can generatefertiliser for agriculture. Where gardensor agricultural fields are close to urbansettlements, their use enables almostall the faeces, along with the otherorganic waste generated at householdlevel, to be used as fertiliser in anenvironmentally friendly way.

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Toilet bowl for separating urine andfaeces developed in South Africa

/87/

Continuously operating compost toilet/86/

3.3 WASTEWATER


Dimensioning

Dry and compost toilets will have tobe designed according to the numberof users and according to the volumeof stools and organic waste to beprocessed. It has to be ensured thatthe material remains in the compost-ing chamber long enough for the fullcomposting process to occur. Indouble chamber systems, the solidcomponents in the unused chambershould be allowed to dry anddecompose completely.

In a continuous composting toilet,material is regularly added and takenout: material that has already com-posted is removed, making space fornew material. Again, sufficient pro-cessing time should be guaranteed sothat the material can completelydecompose.


Operating compost toilets requires ahigh level of user awareness and care.Determining factors will be: humiditylevels, the amount of organic materialadded, which increases the nitro-carbon content, and the processingtimes. As a rule, discontinuouscompost toilets are easier to operatethan continuous systems, whichcannot completely rule out the risk ofcontaminating already compostedmaterial with raw waste or excrement.

With discontinuously operated drytoilets, it is important to ensure thaturine is properly separated fromfaeces, and that the amount ofadditionally needed water, e.g. forcleaning, is kept as low as possible.In order to minimise smell nuisances,ashes or lime should be added aftereach use. As a chamber fills up, thefaeces material dries out; this occursespecially during the storage phase ofthe other full and unused chamber. Incooler or more humid climates, usingsolar heat can support this process.After a drying period of at least sixmonths, most patho-genic germs arelikely to have died, and the drymaterial can be removed and used,e.g. as fertiliser.

In case of composting, it will beimportant to carefully controlhumidity levels (optimum is 40-60%).

Liquid content usually consists ofurine, cleaning water, the natural fluidcontent of faeces and other material,e.g. organic kitchen waste. Thestorage chambers will thus needdrainage or other possibilities offiltering off excess moisture.

For compost toilets, structuralmaterial like organic garden waste(grass, foliage/leaves, etc.), sawdust orsoil will have to be added regularly toachieve appropriate nitro-carbonlevels. Again, it is recommended thatashes, lime or soil be added after eachuse to avoid smell nui-sances.

When a chamber is 3/4 full, usage willhave to be switched to the secondchamber. The material will thendecompose aerobically over a periodof about one year, after which theresultant compost can be removedand used as fertiliser.

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Compost toilet with plastic storage tank/88/


The technical skills needed to build adry or compost toilet are similar tothose needed for the construction ofstandard pit latrines. However, theiruse and operations requires intensiveadvisory assistance and training. Inthis context, community basedorganisations, environmental groupsor other self-help initiatives can andshould have an important role.

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): DRY AND COMPOST TOILETS – SEPARATION OF URINE


Using dry toilets, and in particularcompost toilets, requires significantcare and discipline. As specificprocesses (drying, composting) willhave to take place in the toilet itself,all users have to be aware of theconsequences or their behaviour andusage patterns. To support theseprocesses, some necessary additives(ashes, soil, lime) will have to beavailable and used in an appropriateway. A good amount of knowledge,sensitivity, discipline and acceptanceis required of all users.

As this cannot always be guaranteed,the resultant dried material and/orcompost should always be handledwith care. It should not be simplydeposited on the surface of theground, but instead worked into thesoil. In this way, possibly incompletedecomposing processes can continuewithout major health risks.

Locally produced toilet bowl for urine separation in Kisumu, Kenya /89/

Assessment of Costs

Similarly, the construction costs of dryand compost toilets differ little fromthose of pit latrines, although it maybe necessary to employ more skilledlabour with higher wages, resulting inslightly higher costs.

On the other hand, cost savings arepossible in locations with solid soilconditions, as compost and dry toiletscan be built with comparativelysmaller pits.

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Compost toilet in South Africa /90/

3.3 WASTEWATER


Main FeaturesCost-efficient inexpensive on-site-sanitation option; based on a directseparation of urine and feces; separate treatment and processing (drying,composting) and use (fertiliser)

ApplicationWhere pit or VIP latrines cannot be used because of difficult soil conditions,high groundwater levels or scarcity of space (particularly in dry climates)

CostsLow, as most material needed is cheaply available locally

OperationsSelf-help initiative possible both for construction and operations

InterfacesEmptying of toilet storage chambers and disposal of processed material can bedone by city-wide service providers (municipalities, private sanitation firms), butin most cases, is not necessary

AdvantagesSimple and inexpensive technical solution; use of local material possible; nosewage permeation, i.e. no soil contamination; production of fertiliser; lowrequirements for technical skills for construction

DisadvantagesRequires high level of user care and discipline, and a basic understanding ofcomposting processes

To be ConsideredHygiene aspects of using processed materials in order to avoid infections andother health hazards

Soweto, South AfricaCompost latrines in aninformal settlement

In the informal settlement EliasMofswaledi in Soweto, the GreaterJohannesburg Transitional Metro-politan Council (GJTMC) and theWater Research Commission built300 compost latrines. Maintenancewas taken on by the GJTMC.

A later evaluation of this projectshowed that compost latrines can bea viable and affordable sanitationoption. In spite of high requirementsfor user care and discipline, whichcalled for user awareness campaigns,this solution can be recommended,in particular for dry (arid or semi-arid) climates.

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3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): AQUA PRIVIES / SEPTIC TANKS

Application

In urban areas without the possibilityof connecting to sewage systems,septic tanks are another viable andenvironmentally friendly sanitationoption. Applied for decades in manydifferent parts of the world, septictanks are a well-proven andestablished technical solution for thedischarge of household sewage.

Septic tanks are usually rectangularwaterproof containers installed belowground, and receive wastewater fromtoilets, kitchens and bathrooms. Theycan serve just one household or build-ing or, when connected with a smallnetwork (or settled sewer), a group ofbuildings or households. They can bedesigned as a one chamber or a multi-chamber system.

Septic tanks are based on the prin-ciple of separating solid components(sludge) and liquid components. Afterseparation, the liquid componentsleave the septic tank and are filteredthrough soakage pits or drainagefields and discharged to the soil or asewer system (e.g. a small boresewer); the solid components remainin the septic tank. Anaerobic decom-posing and fermentation processesreduce the sludge volume. Theresidual sludge has to be removed atregular intervals (e.g. every 2-3 years,depending on the size of the tank).*

*In septic tanks for household wastewater, alayer of scum builds up over time close to theinlet. It consists of floating material, such asgrease, oil, hair, small pieces of wood etc.,and of sludge particles that are carriedupwards by fermentation gases. New scummaterial rises and pushes the old scumupwards above the water level where they dryand loose weight, and thus the scum layercontinues to grow. Although this does notaffect the treatment process, it reduces thetank's capacity. The scum layer has thereforeto be removed from time to time.

Technical Solutions

The following basic technical solutionscan be applied:• Aqua privies are one-chamber-

systems, into which faeces andwastewater are discharged belowthe surface level of the tank. Thisreduces smell nuisances in thetoilet to a minimum.

• A standard septic tank consists oftwo chambers. Solid componentssettle in the first chamber, whilethe second chamber is used totreat the liquid components.Wastewater arriving in the secondchamber produces no turbulence;consequently, small lightweightparticles may be suspended withinit.

• Because the purity of thewastewater improves the longer itremains inside the septic tank,three-chamber-systems are used insome countries. All the wastewatergenerated by household toilets,bathrooms and kitchens aredischarged into the first chamber.All three chambers are then usedfor the sedimentation of solidcomponents and theirdecomposition. In the thirdchamber, a partially anaerobic

process further cleans thewastewater, which is alreadylargely free from sediments. Insome cases, the last chamberdirectly serves as a soakage pit. Todo this, it is fitted with a waterpermeable base. As a rule, theoutlets for treated liquids shouldbe below the scum layers thatbuild up in each chamber.

The advantages of septic tanks aretheir low maintenance requirements,the avoidance or limitation of smellnuisances and the possibility of laterconnecting to a sewer system.

Disadvantages are their relatively highinitial investment costs, the operatingcosts of regular emptying and theneed to use sufficient amounts ofwater from toilets, bathrooms andkitchens for flushing. Septic tanks canusually therefore only be appliedwhen households are connected towater.

Construction of a septic tank /91/

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Construction /92/93/

Minimum distances of septic tanks and soakage pits to buildings, infrastructure and naturalfeatures

3.3 WASTEWATER


Type of installation septic tank (m) soakage pit (m)

buildings 1.5 3.0plot boundaries 1.5 1.5wells 10.0 10.0rivers and creeks 7.5 30.0slopes and valleys 7.5 30.0water supply pipes 3.0 3.0streets and roads 1.5 1.5large trees 3.0 3.0

Dimensioning

The volume of a septic tank has to bedetermined in relation to the amountof wastewater to be discharged. A twochamber septic tank should be de-signed to allow the liquid componentsto remain in the system for 1 to 3days; with 3 chamber systems, theprocessing and treatment time couldbe up to 10 days.

In two chamber systems, the first tankis generally twice as large as the sec-ond. For operations, the accumulationof 0.03 - 0.04 m3 of solid material perperson per year has to be al-lowed for.The layer of sludge built up over timeshould not exceed 1/3 of the tank'stotal height. The number of users andthe planned emptying cycle thusdetermines the necessary tankvolume.

Operations

As wastewater treated in septic tanksgoes into the soil, certain minimumdistances to other buildings, infra-structure or topographic features willhave to be considered. The figurespresented by the table below are validfor soils with normal filtrationcapacity.

side section

plan section

AQUA PRIVY

SICKERGRUBE

Schematic sketch of a communal septic tank for a number of households inBengkulu/Indonesia /94/

82

Bengkulu, IndonesiaImproved septic tanks at settlement level In the context of a GTZ demonstration project, improved septic tanks weredesigned, built and tested in two neighbourhoods of the Indonesian city ofBengkulu on the island of Sumatra. The project's objective was to increase theefficiency of the treatment of effluents from septic tanks from BOD5 reductionsof only 20%, to 60%. In addition to the construction of improved (multi-chamber system) septic tanks, other communal sanitary installations, such astoilets and laundry facilities, were rehabilitated.

To complement those measures, approaches to increase resident's participationin decentralised sanitation projects and appropriate financing instruments weredeveloped.

The main conclusions of the model project were that: • Unclear tenure, unfavourable soil conditions and high groundwater levels

hampered the selection of appropriate locations for septic tankconstruction.

• Due to high groundwater levels, the tanks had to be watertight, whichcalled for high requirements with regard to the technical skills of the firmsand labourers commissioned with the construction works.

• The participation of residents and local institutions presented problems.Hence, accompanying awareness campaigns and training in matters ofsanitation and hygiene were indispensable.

• Most residents had difficulties with the high construction costs.Complementary credit programmes were thus necessary.

• The municipal administration was not sufficiently capable of managing theparticipatory approach for decentralised sanitation and needed substantialadvisory assistance.

• It was possible to achieve the intended reduction of wastewater BOD5content in all the tested septic tank installations.


Septic tanks and soakage pits needsufficient space and permeable soilconditions. In densely built-up urbanareas, the space needed is often notavailable. Moreover, soil absorptioncapacities can already be exhausted bylarge numbers of pit latrines, septictanks and soakage pits.

Since they need water for flushing,septic tanks are usually not a viablesanitation option for settlementswithout water supply provisions.

In addition, septic tanks can only beinstalled in places where road andstreet condition allow for the regularemptying and disposal of sludge.

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): AQUA PRIVIES / SEPTIC TANKS

Operating a septic tank requires theregular discharge of water and otherliquids into them. The tank should beregularly inspected in order to ensurethat solid components from the firstchamber are not entering the secondchamber. Moreover, built-up scumshould be removed regularly. To allowand support bacterial decompositionprocesses, the discharge of anychemicals (particularly cleaningdetergents containing chlorine) intothe septic tank should be prevented.

Septic tanks should never be emptiedcompletely. As a rule, about 1/3 of thesludge volume should be left in thetank. This volume of bio mass (andbacteria) will be needed to ensureappropriate anaerobic decomposition.

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3.3 WASTEWATER


Main FeaturesEnvironment-friendly solution for the disposal of household wastewater insettlements that are not connected to sewer systems; joint use by a group ofneighbouring users is possible

ApplicationTakes wastewater from toilets, kitchens and bathrooms in tanks with separationof liquid and solid components

CostsCosts per household 3-5 times higher than for simple latrines

OperationsConstruction and operations by individuals, small-scale enterprises or by mutualhelp at neighbourhood level; financing through local small credit programmes

InterfacesIf necessary, emptying of tanks and disposal of sludge by providers fromoutside the settlement (municipalities, private operators)

AdvantagesTechnology and construction methods well known in many countries; lowmaintenance requirements; partial decomposing of faeces to less hazardousproducts; connection to sewerage possible at later stages of development

DisadvantageInitial investment costs relatively high; regular emptying against fee paymentnecessary; re-quires a certain amount of wastewater from toilets, bathrooms andkitchens for flushing

To be ConsideredChemical contents of wastewater, in particular disinfectants with chlorinecontents, can impede the bacterial decomposing of sludge


The technology of septic tanks is wellknown in most countries. Septic tanksare constructed both individually inself-help and by small enterprises.However, the provision of advise onsuitable locations, operations andmaintenance, and the final disposal ofliquid and solid products may benecessary.

Septic tanks can be constructed withthe mutual help of neighbours andcan be financed by local small-scalecredit programmes. The emptying ofsludge can also be organised at neigh-bourhood or community level, or canbe commissioned to small localenterprises.

In any case, the installation of septictanks is a viable option for improvinghygienic conditions at settlement leveland can be implemented andoperated through self-help.

Assesssment of Costs

Compared to other simpler sanitationoptions, septic tanks are relatively costintensive. The construction andoperating costs per household are 3-5times higher than those for simple pitor VIP latrines. Households thereforerequire a certain minimum incomelevel. Costs can be reduced when agroup of households jointly operates alarger septic tank.

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Biogas plants: Chinese (above) andIndian (below) type /95 a/b/

Toilet connected to a Chinese type biogasplant /96/

Application

Small biogas plants or “biodigesters”*provide a special form of decentralis-ed wastewater treatment. Since theirconstruction requires high initialinvestments, their application in urbanpoor settlements will generally belimited.

On the other hand, biogas plants canbe a viable option for treating waste-water from households, agricultureand some commercial activities,especially because of their environ-mental benefits. In order that thesanitation options presented in thecontext of this publication are ascomprehensive as possible, they aredescribed here as a possiblealternative in specific situations:• for wastewater management in

urban settlements with lowdensities, where sufficient space isavailable and where biomass isalso generated by agriculture orhorticulture.

• for the treatment of wastewaterfrom larger facilities like schools,hospitals or markets, even ininnercity locations. Such solutionswill focus more on treatingwastewater (e.g. infectiouswastewater from hospitals) thanon biogas production. However,the biogas produced can be usedas energy source, and can thussubsidise the costs of wastewatertreatment.

*Larger-scale municipal plants that are usedmore for wastewater treatment than biogasproduction.

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEME): BIOGAS PLANTS

Technical Procedures

Biogas plants can process both solidand liquid organic waste. They canthus be a comprehensive solution forthe disposal of human and animalexcrement, waste from agriculture andhorticulture, and organic residualsfrom food processing (e.g. slaughter-house waste).

On one hand, a biogas plantneutralises wastewater and otherorganic waste. On the other, itproduces valuable fertiliser and biogasas a source of energy.

Biogas plants are particularly efficientwhen solid and liquid waste com-ponents with low carbon and nitrogencontent (faeces) can be mixed withcomponents with high carbon andnitrogen content (straw, gardenwaste), and when temperatures aresufficiently high (30-35°C). Thematerial is fermented by an anaerobicprocess. Bacterial decompositionproduces mainly methane gas (andsome carbon dioxide), which can beused as energy source. The solid resi-dues built up over time inside theplant are a valuable fertiliser and hasto be removed at certain timeintervals.

Construction

Biogas plants can be operated both atneighbourhood level and as largercommunal installations. Depending onconstruction type and technology,they can have a processing capacityranging from just a few cubic metersof wastewater and biomass to somehundreds of cubic meters.

Generally, a distinction is madebetween two different types of biogasplants: those with a fixed top or vault(Chinese type) and those with amovable top or cap (Indian type).

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Gas demands for different uses

3.3 WASTEWATER


Dimensioning

Urban households do usually not produce sufficient animal and agricultural wasteto operate a biogas plant efficiently. In most cases, biogas plants will thereforeonly be useful for large numbers of households or as large-scale installations.

The necessary size of a biogas plant depends on the amounts of wastewater andsolid organic waste components to be processed. Experience from China showsthat the solid and liquid waste generated by one family, complemented by thewaste produced by 1-2 pigs, can be sufficient to operate a small biogas plant. As ageneral rule, the production of 2 m3 of biogas requires organic waste (manure)from 2-4 cattle or 2-3 pigs.

If biogas production as an energy source is the main purpose of a biogas plant, itsdimensioning will have to relate to the amount of gas to be produced rather thanthe necessity of disposing of wastewater and other organic material.

The basis for the dimensioning of biogas plants for large facilities (schoolcomplexes with kitchens, boarding establishments, hospitals etc.) is the volumeof wastewater and organic waste generated per time unit (day, week or month).The plant should be large enough to guarantee that the wastewater within it hassufficient space and hence time to process, in order that anaerobicdecomposition can be complete, and all pathogenic germs are killed.

Operations

Biogas plants are generally operatedcontinuously, i.e. solid material mixedwith water or wastewater feed into tothe plant at regular intervals. Aminimum amount of water (about 10litres per day per person, whenhuman excrement is being treated)will have to be added to this mixturein order to keep it sufficiently liquidand pumpable.

An anaerobic process that kills allpathogenic germs occurs inside thebiogas container. The necessaryprocessing time inside the plant isdetermined by the container size andthe volume of material to beprocessed. Generally, a processingtime of 40-50 days will be needed. Thesolid residues produced are rich innutrients, and can be used, dried orcomposted or as liquid fertiliser, foragricultural purposes.

The simple Chinese type of con-struction, with a fixed top built ofbricks, is vulnerable to gas leakagesand losses when, as a result ofdiscontinuous operations or theremoval of solid residues, changinggas pressures cause cracks in thebrickwork.

In contrast, the “floating” cap of theIndian type guarantees a constant gaspressure. However, the cap, usuallybuilt from sheet steel, is often subjectto corrosion problems. The Indiantype is technically more sophisticatedand more expensive.

Use type of consumption gas demandequivalent to (cbm/h)

cooking 2 fire places 0.334 fire places 0.476 fire places 0.652-4 fire places 0.20-0.45per capita and day 0.35-0.45

lighting electric lamp with 100 W 0.13single mantle lamp 0.07-0.08

machines modified to gas motors 0.61-0.68per kWh

cooling for 100 litres 0.10

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Practical application of biogas plants

Small-scale biogas plants are most commonly found in Asia. In China alone, it isestimated that there are 7 million biogas plants at household level, which areoperated with excrement from household members and 1-2 cows or pigs, andorganic household and agricultural waste. They produce sufficient gas forhousehold cooking and lighting. Biogas plants are also common in India, whereat least 750,000 small biogas plants are estimated to be used at household level.

In Nepal, the first biogas plants were set up on an experimental basis in 1955:by July 1995, their number had increased to 24,000. Current estimates based onthe total volume of biomass (manure) generated and the average size ofhouseholds using biogas (5.5 persons and 4.7 live-stock), put the possible totalnumber of biogas plants in Nepal at 1.3 million.

Within the framework of the “Community Mobilisation Process” of the “RuralEnergy Programme”, 15 biogas plants were established in the village of Khalte inthe District of Tanahun. All the plants have a tank volume of 6 m3 and aregenerally operated for 4 hours daily - two hours in the morning and two hoursin the evening. They produce sufficient gas to run a stove for four hours. Eachhousehold uses about 36 kg of biomass (manure) per day, mainly from thehousehold's livestock (buffalos, cows, pigs and goats), and roughly the sameamount of water.

Modern biogas use in Europe and the USA mainly involves the collection andprocessing of gas from sanitary landfills and the operation of so called “bio-digesters”. These are large-scale installations with relatively sophisticated technology(tube extruders, heating, electronic control instruments, etc.), and are principallyused to process wastewater and other organic waste. The gas is produced byanaerobic processes similar to those in conventional biogas plants, and is mainlyused as an energy source for the plant itself (for heating, generating electricity etc.).The treated wastewater and sludge produced is valuable as fertiliser..

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): BIOGAS PLANTS


To guarantee the efficiency of a biogasplant, all necessary operations (e.g.the introduction of new material) haveto be done regularly and with a highlevel of discipline. Furthermore, toproduce gas constantly, the materialto be processed will have to beavailable regularly and in similarvolumes and compositions. If this isnot possible, continuity will have tohave to be ensured by using stored,thinned down or acquired additionalwaste material.

The construction of biogas plants alsorequires building workers to havespecial technical skills.

The dealing with human and animalexcrement intensively, as occurs withbiogas plants, is not acceptable in allcultures, and is sometimes onlypermitted to certain social groups.Moreover, the perception of usingproducts from human or animalexcrement (i.e. biogas) for cookingpurposes may be difficult to accept insome cultural contexts.

To facilitate the use of faeces,wastewater and other organic waste,biogas plants should be located closeto residences or animal stables. Inaddition, gas pipes should be as shortas possible to avoid or limit leakages.Sufficient space to construct the plantshould therefore be available in thedirect vicinity of toilets, bathroomsand kitchens, and also be close to therooms where the biogas will be used.

Construction of a Chinese type of biogas plant /97/

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3.3 WASTEWATER


Main FeaturesNeutralisation of solid and liquid organic waste and wastewater; production ofvaluable fertiliser and of biogas as an energy source

ApplicationDisposal of wastewater from households, agriculture and some commercialactivities

CostsHigh, will have to be supported by appropriate financing instruments

OperationsCan be operated by individual households, NGOs, public institutions or privateenterprises

InterfacesIf necessary, emptying and disposal of residues by service providers fromoutside the settlement (municipalities, private operators)

AdvantagesBiogas plants can be operated both at individual household level and ascommunal facilities; they are a comprehensive and environment friendlysolution for the disposal of organic waste and human and animal excrement,whilst simultaneously producing fertiliser and biogas

DisadvantagesConstruction and operations of biogas plants need special technical skills andknow-how; they must be operated with great regularity and discipline

To be ConsideredDealing with human and animal excrement intensively, as is involved, is notsocially acceptable in all cultural contexts


Due to demanding building techni-ques and the technical skills neededfor operations, the introduction ofbiogas plants has to be accompaniedby technical and organisationalsupport and advice. This can beprovided by community organisationand/or NGOs that have the necessaryexperience and expertise.

With adequate support, biogas plantscan be constructed and operated byresidents' self-help groups, or byinitiatives by local schools, hospitals orother public institutions.

Because the construction of biogasplants calls for substantial financialresources, such initiatives will alsohave to be supported financially, e.g.by small loan funds, savingprogrammes or the acquisition ofdonations.

Assessment of Costs

In most cases, the construction costsof biogas plants will be difficult forindividual households to afford.Communal solutions, or joint ini-tiatives by a group of people, familiesor institutions, will usually be lessexpensive than individual plants.

In larger scale biogas installation (e.g.for hospitals), the gas produced canbe used to meet energy demands andthus subsidise the costs of wastewatertreatment.

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Schematic sketch of a grease trap made from metal or plastic parts inside a concreteand/or brickwork tank /99/

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): GREASE TRAPS

Technical Solutions and Dimensioning

Grease traps are devices that separate grease, oil and other lubricants fromgrease-water mixtures.

Simple grease traps can be produced locally without the need for specialmachinery or equipment. They should consist of a simple waterproof tank fittedwith parts welded from metal (preferably high-grade steel) or made from PVCsheets, or cast from glass fibre reinforced synthetic resin.


Grease traps or separators areinstalled in wastewater outlets andoperate continuously without specificmaintenance requirements. Oil andgrease is separated on the principlethat the density of oil or grease isdifferent to that of water (hence oil orgrease floats on water).

Following a rough pre-filtration(which separates out solid items suchas food residues, sand or stones), themixture of water and grease/oil entersinto the trap's main chamber. Themixture remains long enough insidethis chamber to allow the oil andgrease components to rise and settleat the surface. The oil and grease freewater is then discharged from themain chamber via an outlet below itssurface level.

Application

In urban poor settlements, as in otherresidential areas, the oil or greasecontents of wastewater can causeserious environmental pollution wheneffluents are discharged in ground orsurface waters.

Wastewater from kitchens (particularlyfrom the large kitchens of schools,factory canteens, restaurants, andhospitals), as well as cleaning andsurface water from workshops,garages, petrol stations and transportcompanies, can contain significantamounts of grease, oil and otherlubricants.

Grease separators are especially usefuland necessary for environmentalreasons when wastewater can directlyinfiltrate the soil or is dischargedwithout treatment into creeks, riversand other surface waters.

Technically simple forms of greasetraps or grease separators can be usedfor small-scale enterprises or similaractivities in urban poor settlementsthat generate wastewater with highgrease or oil contents.

The only maintenance required isregular cleaning of the pre-filtrationsieve and the removal of the oil andgrease. Depending on the volume ofwastewater and the amount of oil andgrease, this will have to done once aday or every few days. Regularcleaning is important in order tomaintain the trap's efficiency and toavoid smell nuisances fromdecomposing processes.

When the separated grease consistsmainly of cooking fats, it can be fed topigs. Mineral oil or other greaseresidues have to be incinerated inspecial furnaces or deposited in aproper manner at landfills.

Groundwater pollution from a vehicledepot /98/

long section cross sectionA - A

cross sectionB - B

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3.3 WASTEWATER


Main FeaturesSeparation of oil and grease from wastewater of canteen kitchens andworkshops based on the difference in density between water and oil / grease

ApplicationWhere large amounts of oil or grease are discharged into wastewater; greasetraps are installed in wastewater outlets, close to the wastewater source

CostsCan be manufactured at low costs; operations involve little or no costs

OperationsCan be produced and installed locally through self-help

InterfacesLarge amounts of oil and/or grease residues will have to be disposed of outsidethe settlement (landfills, incineration, recycling)

AdvantagesSmall, simple and inexpensive; continuous mode of operation without specificmaintenance requirements; where residues consist only of cooking fats, theycan be fed to pigs

DisadvantagesGrease dissolved by detergents cannot be separated; proper disposal of oiland/or grease residues can be problematic

To be ConsideredRegular cleaning necessary to maintain efficiency and to avoid decompositionand associated smell nuisances


Large amounts of detergent inwastewater can dissolve its greasecontent so that it cannot be separated.In order that the maximum amount ofgrease fractions can be separated, thedetergent content of kitchen waste-water should be kept as low aspossible.

Appropriate disposal of greaseresidues can be another problemwhen access to landfills orincineration facilities is difficult.


Grease traps are small, simple andinexpensive devices. Theirdeployment depends less oninvestment costs or operationsrequirements than on potential usersbeing convinced about their benefits.This may have to be supported byawareness campaigns, which can beundertaken by local environmentalinitiatives or community associations.Where local businesses or other usersare convinced and willing to use them,simple grease traps can be producedand installed locally through self-help.

Assessment of Costs

Technically simple grease traps can bemanufactured at reasonable costs andcan be installed without the need forlarge investment.

Their operation involves little or nocosts; some time needs to bededicated to cleaning and the removalof oil and grease deposits.

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Schematic sketch of a drainage field /100/ Schematic sketch of soakage pits /101/

3.3 WASTEWATER


SOLUTIONS AT SETTLEMENT LEVEL (ON-SITE SYSTEMS): SOAKAGE PITS • DRAINAGE FIELDS

Application

In urban poor settlements, a soakagepit or drainage field can be analternative to a connection to a sewersystem under the followingconditions: • When the solid components of

toilet effluent are separated fromthe liquids (e.g. in septic tanks,aqua privies or dry toilets), theremaining wastewater is largelyfree of hazardous components andcan be discharged together withgrey water from kitchens andbathrooms.

• Where space is available and thesoil is permeable enough toabsorb discharged wastewater.

• Where there is no risk of nearbywater sources (e.g. wells) beingcontaminated by infiltratingwastewater.

Soakage pits and drainage fields areclassical approaches to wastewaterdisposal, and can be found in manycountries and regions.

Technical Solutions

Infiltrating wastewater into the soil is a well-proven method of disposing of lesshazardous wastewater and grey water. It is based on the filtering and cleaningcapacity of soils and vegetation. Two basic solutions are possible:• Where sufficient space is available, wastewater can be infiltrated into drainage

fields.• Where space is scarce, soakage pits built of brickwork or filled with coarse

gravel and stones can be used.

Small sand filters can be used to treat grey water on its own for irrigationpurposes. /102/

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3.3 WASTEWATER


wastewater and the amount ofmaterial suspended in it, a film ofalgae builds up and the filtration poresbecome clogged. When this happens,the drainage field has to be relocatedor closed for a certain time to allowthe algae film to dry and degrade.


The possible usage of soakage pitsand drainage fields is largelydetermined by the space available andthe soil's filtration capacity. Negativeimpacts on drinking water sourcesand installations have to be avoided.In densely built-up urban settlements,infiltration and soakage are thus oftennot viable sanitation options.


The technology is simple and can beused by private households and localcraftsmen. Assistance may be requiredin selecting appropriate locations andsoils. Design and construction can becoordinated and carried out throughself-help.

Assessment of Costs

The main costs of constructingsoakage pits or drainage fields will belabour costs. It may be necessary topurchase or at least transportappropriate filtration gravel. Indrainage fields, drainage pipes will bea major investment item. Generally,costs will be reasonable and locallyaffordable.

Dimensioning

The size of soakage pits and thenecessary lengths of drainage pipesdepends on the volume of wastewaterto be filtered and on the filtrationcapacity and permeability of the soil.As soil conditions can differconsiderably even in small areas,general recommendations are difficultto be made. In most cases, an analysisof soil conditions and/or practicaltests will be necessary.

The same applies to the dimensioningof grey water filters, which is also besttested in practice. It depends on thevolume of water and the type of filterto be used (surface, thickness oflayers, gravel and sand grain sizesetc.). As a rule, 10-20 m of drainagepipe will be needed per inhabitantconnected to the filter.

Soakage pits or drainage fields shouldnot be located where they might havea negative affect on potable waterinstallations, water intakes, surfacewaters or other infrastructure facilities.Necessary minimum distances to suchinstallations are similar to those forseptic tanks (see section on septictanks).


Wastewater should be dischargedcontinuously to soakage pits anddrainage fields; sudden large intakesof wastewater should be avoided.Flooding of filtration installations byheavy rainfalls should be prevented, asthe resulting possible dispersion ofpathogenic germs risks exposing thepopulation to infections.

The filtration capacity of drainagefields normally decreases over time.Depending on the salinity of the

Main FeaturesFiltration of sewage and greywaterfree of solid components, based onthe filtration and cleaning capacity ofsoil and vegetation

ApplicationFor low-density settlements withoutpossibilities of connecting to a sewersystem

CostsMainly labour costs; limitedinvestment costs (drainage pipes)that can generally be financed locally

OperationsConstruction and operations in self-help possible

InterfacesNone

AdvantagesTraditional approach to wastewaterdisposal; well-known in manycountries; simple technology, can beapplied by individual privatehouseholds and local craftsmen;inexpensive

DisadvantagesApplication limited in densely built-up areas and by filtration capacity ofsoils

To be ConsideredLocations should be selected in waysthat do not negatively affect drinkingwater resources or surface waters.

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Bucket latrines /104/


There may still be pathogenic germsin the solid, paste-like or liquidresidues that are being emptied andtransported. Basic precaution willtherefore need to be taken in thehandling of tools and equipment(workers should avoid contact withresidues), in transport (leakages are tobe avoided) and in final disposal(groundwater pollution andcontamination of agricultural fields isto be avoided). Moreover, cleanlinessand hygiene should be observed(protective clothing should be worn,personnel should wash and avoideating at work).

The selection of further processingand final disposal methods shouldtake environmental aspects intoaccount and protect the populationfrom health hazards.


Due to the usually large volumes ofmaterial to be removed and disposedof, the option of transportingmanually in buckets, tubs or barrelswill generally be limited.

3.4 WASTEWATER

WASTEWATER DISPOSAL

OFF-SITE-SYSTEMS: TRANSPORT CONTAINERS • VEHICLES

Application

Almost all on-site sanitation options(different types of latrine, composttoilets, septic tanks and aqua privies,biogas plants etc.) need to be emptiedregularly and sludge and otherresidues have to be disposed of.

For this purpose, various methodsusing containers and vehicles can beapplied.

In urban poor settlements, most ofthese methods are well-known andproven solutions. They can be tailoredto meet the specific conditions andsituations of the different types ofsettlement that need off-site disposalof sludge and other wastewaterresiduals.

Technical Solutions

Depending on the type of on-sitesanitation installation, two basicsolutions for disposing of wastewaterresidues are possible:• The decomposed paste-like

residues (sludge) of pit, VIP andpour-flush latrines, of septic tanksand, in particular, of biogas plantsare liquified by adding water,pumped out and removed bytanker trucks.

• The more solid residues producedby compost and dry toilets, or thedried-up material in latrines, septictanks and biogas plants, areshovelled out and loaded ontocarts or trucks for transport.

The selection and dimensioning ofcontainers and vehicles depends onthe type of sanitation option, theconsistency of the residues and, inparticular, the possibilities of access(street conditions and width).

It will be important to leave part ofthe residue in the sanitation pit as a“bacterial start-up” to facilitate a newdecomposition cycle.

Emptying a septic tank with a small suction tanker /103/

Bucket latrines are aspecial type ofsanitationinstallation that isstill found in someparts of Asia andAfrica. Excrement iscollected in bucketsand removed daily.

Their acceptance,however, is rapidlydecreasing, even inurban poorsettlements.

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Barrel cart for emptying latrines in Asia/105/

3.4 WASTEWATER

WASTEWATER DISPOSAL

Suitable end processing and disposalfacilities are needed to prevent localsanitation and hygiene problemsbeing simply exported outside thesettlement. Furthermore, householdshave to be willing and able to payappropriate fees for emptying andtransportation services.

In addition to the technical andfinancial aspects, cultural or religiousreservations may have also to be takeninto consideration in some countries.


The emptying of latrines and septictanks can be carried out through self-help. If this is organised as mutualhelp at community level, labour costscan be reduced and individualhouseholds would just have to pay forthe tanker truck's fuel and possibly itsrental.

The service can also be provided bylocal small-scale enterprises. In thiscase, service fees will have to be paid.

Assessment of Costs

The main cost item will usually be theservice fees to be paid to local small-scale private enterprises. Whenemptying is undertaken with self-help,a financial share of the purchase (orrent) and operational costs of vehicleswill have to be paid in addition to thein-kind contribution of labour.

The initial investment costs of large,communally operated tanker truckswill be a major item. In addition,operational (diesel fuel, lubricants)and maintenance costs (spare parts,regular servicing) will have to becovered.

Main FeaturesEmptying of on-site systems (e.g.latrines, septic tanks, etc.) andtransportation of residues

ApplicationManual or mechanical emptying andtransportation, depending on(vehicle) access and the compositionof the residues; selection of types ofcontainer and modes of transportdepends on the consistencies andtypes of residue

CostsLabour costs, and investment andoperating costs of equipment

OperationsCan be carried out in self-help ormutual help, or as service of localsmall-scale operators

InterfacesWhere necessary or possible,emptying of pits and disposal ofresidues by outside service providers(municipalities, private enterprises)

AdvantagesRegular emptying ensures on-sitesanitary facilities are continuouslyavailable for use; possible job andincome creation; self-help possible

DisadvantagesTransportion by vehicles oftenrestricted due to difficult access;manual transport in buckets, barrels,etc. only possible for smallervolumes

To be ConsideredHygiene, technical and economicaspects; cultural or religiousreservations in some countries

Dar es Salaam, TanzaniaManual Emptying ofLatrines The “Manual Pit Latrine EmptyingTechnology (MAPET)” is a methodthat combines traditional and modernapproaches. The Dar es SalaamSewerage and Sanitation Department(DSSD) uses it in settlements thatcannot be accessed by large suctiontrucks. Emptying is done using asimple pump and a drum system,which is transported on speciallydeveloped push carts with bicycletires.

The simple pumping and storagetechnology has replaced unhygienicmanual emptying with buckets. Theequipment is inexpensive and can belocally manufactured by smallworkshops.

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3.4 WASTEWATER

WASTEWATER DISPOSAL

OFF-SITE-SYSTEMS:CONVENTIONAL AND UNCONVENTIONAL SEWER SYSTEMS

Application

In most cities, especially in moredensely built-up areas, waterbornesewerage is the most common andwidespread form of dealing with non-industrial effluents. Wastewater iscollected in pipe systems andsubsequently discharged at treatmentplants, or in watercourses (rivers,canals, etc.) or the sea.

Piped sewerage will also often be themost appropriate and efficientsolution for improving sanitary andhygiene conditions in many urbanpoor settlements, most of which havevery high residential densities.

However, conventional seweragesystems may not be feasible becauseof the high costs of initial investmentsin installations and construction, andof operations and maintenance.Alternative low-cost solutions withreduced technical standards willtherefore be the preferred option.

Technical Solutions

There are several distinctions between conventional and unconventional pipedsewerage systems, but as there are smooth transitions between both types, onlytheir major differences and characteristic features are described in the following:

Condominial sewer systems: Incondominial systems, wastewaterpipes with small diameters (100-150mm) are laid with small gradientsrelatively close to the surface. Incontrast to conventional systems,there are no collector mains. Instead,sewage pipes are laid house to house(across the private plots). Connectiondistances are kept as short as possiblebecause a large number of householdsdischarge into the same pipe. Formaintenance, small inspectionchambers are installed instead of largemanholes.

Simplified sewer systems operateon the principle of conventionalwaterborne sewerage, but for smallervolumes of wastewater and with pipesof small diameter laid close to thesurface. They are designed in a way

Conventional sewer systems, functioning on the principle of waterborne andregularly flushed piped networks, are characterised by large collector mains,which are usually laid with relatively large gradients in the middle of streets. Eachbuilding or plot connects to the mains through smaller connection pipes. Toallow for inspection and maintenance, the mains have manholes at regulardistances. In addition to sewage, the mains are often also sized to receiverainwater and other surface water. Flow through the pipe network is usuallyachieved through gravity. The collected wastewater is carried through the pipesystem to a central treatment plant, or to watercourses or the sea, where it isdischarged.

Uncontional sewer systems do without collector mains in streets. Thewastewater generated in a neighbourhood or settlement is collected andtransported in smaller and more shallowly laid pipes to small decentralisedtreatment plants or to larger sewer mains outside the area.

The most important types of unconventional sewer systems are:

that all household wastewater isconducted to larger mains directly, i.e.without any intermediate interceptortanks for separating out solidcomponents.

Settled sewer systems are based onseparating solid components fromwastewater. They are particularlyappropriate where septic tanks havealready been established, but wherethe amount of wastewater exceeds theabsorption capacity of the soil. Sewagefrom one or more households is firstcollected in an interceptor tank (aone-chamber pit), where solid com-ponents are separated out throughsedimentation. The wastewater is thendischarged from the pit into smalldiameter pipes (so-called small boresewers).

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3.4 WASTEWATER

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Dimensioning

Conventional, simplified and settledsewer systems all need a certainamount of water to move thewastewater through the pipes.Therefore a water connection and aflush toilet is usually required. Toensure the proper transport of faecesand sufficient self-cleaning, pipes willrequire a gradient of about 1:120, anda flow velocity of at least 0.5 m/s.

In settled sewer systems, wastewaterfree of solid components can movewith a lower flow velocity (ca. 0.3 m/s,equivalent to a gradient of 1:220).Since only liquids are beingconducted, pipes can, in certain cases,even be laid uphill (i.e. with negativegradients), so long as the finaldischarge outlet is lower than thelowest inlet (on the principle thatflowing water in an interconnectedsystem will fall to the lowest point). Settled sewer systems consist of thefollowing components:• A house connection to the inlet of

the interceptor tank, from which allhousehold wastewater (excludingrainwater) is discharged into thesewage system.

• An interceptor tank, an under-ground waterproof tank with aninlet and outlet, which should havethe capacity to contain the effluentgenerated over 12 to 24 hours toallow for the sedimentation of itssolid components. Generally, suchtanks are designed as one-chamberpits

• Small sewer pipes made of plasticsor ceramics, laid underground.

In extremely flat areas, it may also benecessary to install pumping stations.

Type water consumption pipe diameters solid components gradient

conventional high large exist highsystems

unconventionalsystems• simplified sewer low small exist high

systems• settled sewer low small separated not

systems necessary• small-bore low small separated low

sewer systems• condominial moderate small possible low

sewer systems

Sewers can either be laid as a con-dominial system inside housing

blocks, or outside of them, beneaththe sidewalks or streets.

/106/

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3.4 WASTEWATER

WASTEWATER DISPOSAL

OFF-SITE-SYSTEMS:CONVENTIONAL AND UNCONVENTIONAL SEWER SYSTEMS

• Reduced water consumption:In contrast to conventionalsystems, sewer pipes need not bedimensioned to carry largeamounts of solid material, andtherefore need less water forflushing. Settled sewer systems arethus particularly appropriate fordischarging small amounts ofhousehold wastewater (as is thecase in many urban poorsettlements).

• Lower pipe laying costs: Due tothe prior separation andsedimentation of solids, pipes canbe laid with low gradients and canbetter follow the ground contoursand topography of a settlement.

• Lower material costs: Variationsin discharge flows are easier tohandle: interceptor tanks even-outtemporary high dischargevolumes, so pipes can have lowertechnical standards and arecheaper than those in othersystems.

• Reduced need for treatment:Some treatment stages, such asscreening, removal of sludge orfermentation in an anaerobicbasin, are not necessary as theseprocesses already take place insideinterceptor tanks.

Consideration should be given toincorporating inspection chambers insettled sewer systems to facilitatemaintenance and cleaning.


In condominial sewer systems, largeparts of the network run throughprivate property. Municipal or otheroperators will therefore have to agreeto take on the responsibility foroperating and maintaining sewers onprivate land in housing areas, inparticular for repair works and theremoval of possible blockages.

If the operator is not willing toassume this function, self-help and theparticipation of users will be necessaryto maintain the system. As wastewateris discharged to sewers in sequence, alack of maintenance in just onehousehold (resulting, for example, ina blockage) can affect a whole block ofbuildings or the entire settlementnetwork.

The main disadvantage of settledsewer systems is the need to regularlyempty and dispose of the sludge inthe interceptor tanks.


A high level of user participation willbe necessary, at least duringconstruction, but also, where possible,in subsequent operations andmaintenance. As most pipes in acondominial sewer systems go acrossprivate property, the support andparticipation of each individualhousehold will be essential.

In general, the success and efficiencyof these kinds of unconventionalsewer systems largely depends on thecollaborative efforts of operators(municipal or private), localcommunity associations or politicalbodies, and individual households.

The required pipe diameters (as ageneral rule, 100 mm or 150 mm areneeded for simplified and settled sewersystems) are determined by thewastewater volume, which in turndepends on the number of householdinlets and on the connectedhouseholds' living standards. For houseconnections, pipes with diameters of75 mm would be sufficient in mostcases. The necessary underground pipedepth and earth cover is defined by thepipe material used and by the expectedweight loading (e.g. the weight ofvehicles when pipes are laid in streetsor roads). For small bore pipesnormally used in simplified and settledsewer systems, a cover of 50 cm will inmost cases be sufficient.

Operations

In spite of small diameters and lowgradients, simplified sewer systemscan conduct large volumes ofwastewater. System blockages occuronly rarely. Even in the upper parts ofa network, where discharges usuallytend to bunch together, wastewater(including solid components) flowswill be sufficient, as the sequence offlow-sedimentation-flow is moreefficient in small pipes.

Wastewater from simplified sewersystems need subsequent anaerobictreatment. This also applies to settledsewer systems, although partialanaerobic cleaning already takes placein the interceptor tanks.

The collection of wastewater free ofsolid components in settled sewersystems has four major advantages:

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3.4 WASTEWATER

WASTEWATER DISPOSAL

Karachi, PakistanOrangi Pilot ProjectIn Orangi, the largest informalsettlement in the city of Karachi,sewage was discharged into opencanals causing serious health hazardsto the residents.

In a participatory approach, the NGOOrangi Pilot Project Research andTraining Institute (OPP-RTI) planneda new sewage system for the wholesettlement in close cooperation withresidents, represented by lanemanagers, and the municipaladministration. Between 1981 and2000 approximately 90% of the ca.104.000 households were connectedto the new sewer system.

The settlement was connected toexternal sewer mains using settledsewers and simplified sewers laidshallowly in streets and lanes. Theresidents paid for house connectionsand pipes to the sewer mains, whichwere extended and refurbished withmunicipality financing.

Through mobilisation, training andadvisory assistance, OPP-RTI enabledresident groups, each from about 30-40 households, to execute thenecessary works in theirneighbourhood (lane). The self-helpapproach reduced construction costssignificantly. Users' financialcontributions were facilitated by aprevious savings plan combined witha small-scale loan programme.

u More details on the Orangi PilotProject can be found in Volume1, “Basic Concepts”, of thispublication series.

Main FeaturesAccording to the type of sewersystem: shallow laying of pipes withlow gradients; prior separation ofsolid components; small pipediameters; pipes laid on private plots

ApplicationCost efficient and water savingalternatives to conventionalsewerage; appropriate for urbanpoor settlements

CostsBecause of the previous features,construction and operation costs canbe significantly reduced (to about30-80% of conventional systems)

OperationsCan be constructed and operatedthrough community self-help

InterfacesIn most cases, wastewater dischargesinto municipal sewer systems or tosmall decentralised treatment plants

AdvantagesRelatively low costs due to simplesewer pipe-work

DisadvantagesHigh level of organisation andparticipation of residents requiredwhen systems have to be operatedand maintained through self-help

To be ConsideredRegular emptying of interceptortanks in settled sewer systems

The system will only function with theactive support of all stakeholders. Inthis context, local self-help groups willplay an important role in raising theawareness and motivation ofresidents, and in coordinating thecooperation of all those involved.

Assessment of Costs

Compared to conventional systems,condominial sewer systems will beconsiderably less expensive chieflydue to the use of small bore pipes andshallow pipe trenches. Using smallinspection chambers instead of largemanholes also saves costs. Theconstruction costs of settled sewersystems largely depend on whetherthe households to be connectedalready have septic tanks.

As a rule, simplified sewer systems willbe 60-80 % less expensive thanconventional systems, while settledsewer systems will be 30-50 %cheaper. However, actual costs mayvary considerably according to localconditions (topography, soil, etc.).

Schematic sketch of a decentralised treatment plant with different ponds and treatmentstages /107/

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3.5 WASTEWATER

WASTEWATER TREATMENT AND PURIFICATION

DECENTRALISED WASTEWATER TREATMENT PLANTS AT SETTLEMENT LEVEL

Technical Solutions

In decentralised wastewater treatmentplants in settlements, wastewater fromone or more settlement is collectedand treated in a number of stages.Treatment is usually done in variousbasins or ponds: • anaerobic basins (separation of

solid components, anaerobicfermentation);

• facultative basins (sedimentationof residual solids, aerobicdecomposition);

• oxidation basins (aerobicdecomposition, also often in theform of fish ponds);

• plant (i.e. vegetation) treatmentbasin (optional).

This type of wastewater treatmentdoes not involve mechanicalequipment. In larger plants, revolvingplates, spirals or injectors are used toaccelerate aerobic decomposition *.

For small decentralised plants,traditional treatment in three stages,

using three basins, will usually besufficient. If wastewater is collected ina settled sewer system, the anaerobicbasin will not be necessary becauseseparation of solid components andanaerobic fermentation has alreadytaken place in septic tanks orinterceptor tanks.

In settlements at the urban fringe orin peri-urban settlements withsufficient space, oxidation basins canbe designed as fish ponds, or (insteadof oxidation basins) as plant treatmentlagoons, with or without infiltration.

* The most modern wastewater treatmenttechniques involve numerous other more complexand technically challenging procedures. As theywould not be applicable or relevant in the context ofurban poor settlements, they are therefore beyondthe scope of this publication.

Application

Small decentralised wastewatertreatment plants at settlement levelcan be a viable disposal option whereno central treatment facilities exist, orwhere a connection to centraltreatment is too expensive andtechnically difficult.

Decentralised plants have been usedfor many years, mainly in the contextof pilot projects, for the treatment ofwastewater from smaller urban orrural settlements, predominantly inindustrialised countries.

In developing countries, such plantsare mainly used by commercialfacilities, such as factories,slaughterhouses or paper mills. Insome cases, the wastewater of largehospitals is also treated decentrally.

Small decentralised installations canalso be appropriate in principle forurban areas in developing countriesthat have no connections to municipalsewage systems. For urban poorsettlements, they can be a technicallysimple and cost efficient alternativefor wastewater treatment when thereis sufficient space near to thesettlement.

99

Results of a three-stage treatment

3.5 WASTEWATER


Dimensioning

A decentralised treatment plant and itsdifferent basins will have to designedand dimensioned according to thefollowing parameters: • the volume of wastewater to be

treated;• the amount of solid components,

BOD5 and COD in the wastewater;• the average ambient temperature;• the oxygen supply (to

anaerobic/aerobic basins).

As little data based on practicalexperience is available it will usuallybe necessary to use empiricalapproaches for the design anddimensioning of basins (e.g. theexpected quality of wastewater aftertreatment).

Anaerobic basin: Due the anaerobicprocesses inside the basin, the volumeof wastewater will be the major factor.

Facultative basin: The basin'ssurface area will be important foraerobic processes.

Oxidation basin: The main designcriterion is usually to ensure thedecomposition of faecal coliforms.

Treatment basins usually have arectangular form with a length towidth of 2 or 3:1. To avoid potentialerosion from effluent washing upagainst the basins' rims, these shouldbe slanted at an angle of about30°.The bottom should be waterproof,which can be achieved by using a layerof natural clay or a suitable plastic foil. According to EU environmentaldirectives, effluent from planttreatment ponds with a treatmentcapacity of >8m3/d will have tocomply with the following minimumstandards:

BOD5 <40 mg/l; COD<150mg/l

In most developing countries, suchenvironmental standards do not exist.Even where they have been intro-duced, they are rarely controlled ormonitored.

u Further design details andparameters can be found inspecialised technical literature.


Organic substances (BOD5) inanaerobic basins should not exceed400 g/m3 in order to avoid majorsmell nuisances. The pH-value shouldnot be acidic and, if necessary, beregulated to a value of 7-8 by addinglime water. Sludge should be removedwhen it has reached half the totaldepth of the basin.

Sludge should be emptied fromfacultative basins when it has reached2/3 of their total depth. In facultativebasins fed from an anaerobic basin ora settled sewer system, sedimentationof solid components will normally bevery limited.

Processing time is 5-10 days inoxidation ponds, which are usuallyarranged as 2-3 basins in a row. Aftertreatment, the number of faecalcoliforms should have been reducedto <30 pro 100 ml.

Sample treatment time BOD5 suspended faecal intestinalsolid components coliforms nematode eggs

(days) (mg/l) (mg/l) (no) (no/l)

Raw wastewater - 240 305 4.6 x 107

804Wastewater quality:•stabilisation basin 6.8 63 56 2.9 x 106 29•facultative basin 5.5 45 74 3.2 x 105 1•oxidation basin 1 5.5 25 61 2.4 x 104 0•oxidation basin 2 5.5 19 43 450 0•oxidation basin 3 5.8 17 45 30 0

100

Obregon, MexicoCombined Wastewater Treatment: Sunwater WastewaterTreatment Project The private enterprise Sunwater Systems Inc. of San Diego, California, hasembarked on a joint venture with other San Diego firms and a Mexican partnerto construct and operate a wastewater treatment plant, based on the “SunwaterSystem”, for 300.000 inhabitants in the city of Obregon, Mexico.

Wastewater is treated as a “living stream” in a sequence of ponds, lagoons andcanals, in which sunlight and fast growing organisms are used as catalysts. Thesystem is designed to specific local conditions and comprises a series of“aquacells”. Each cell contains various living organisms that ferment andbiologically decompose wastewater in different stages.

Wastewater flows through the “Sunwater System” by gravity, and various typesand combinations of bacteriae, algae and water plants raise its level of purity ateach stage. Wastewater can can be processed to different qualities and standardsby altering the number of aquacells and adjusting the processing time, and canalmost reach the quality of potable water, if required.

In more detail, the Sunwater System consists of the following components: • covered anaerobic ponds or tanks;• a two-stage ventilated facultative lagoon; • a high-rate algae system;• treatment by duckweed and the biomass of other water plants; • a system of fish ponds using biomass from algae, duckweed and other plants

as fish feed;• a system to clean fish for marketing;• cultivated marshland for the infiltration of treated wastewater.


The main limitation of decentralisedtreatment plants in urban poorsettlements will usually be the scarcityof space, particularly when a largenumber of ponds or basins arenecessary.

More compact, less space consumingalternatives, such as biodigesters orfermentation towers, are considerablymore expensive. They cannottherefore be used in urban poorsettlements without major financialsubsidies.

To achieve sufficient treatment andpurification effects, some basicoperational parameters (wastewatervolume, treatment time, ventilationand oxygen supply) will have to becarefully considered. This requiresskilled personnel, and disciplinedoperations and maintenance. Theoperating staff will also have toconsider seasonal climatic conditions(heat, drought, heavy rainfall, frost).


Decentralised wastewater treatmentplants are complex installations thatcannot be operated by individualhouseholds or small self-help groups.

If public sector or municipalinstitutions, or private enterprises arenot willing or interested in taking onthe operations of such plants, theycould possibly be carried out bysuitably stable communityorganisations that are sufficientlycapable and willing to acquire thenecessary skills. The financing ofoperating costs will, in any case, haveto be secured by user fees and othercontributions from the community.

3.5 WASTEWATER


DECENTRALISED WASTEWATER TREATMENT PLANTS AT SETTLEMENT LEVEL

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3.5 WASTEWATER


Main FeaturesTreatment and purification of urban wastewater before discharge into surfacewaters; phased treatment process consisting of separation of solid components,anaerobic fermentation and aerobic decomposition

ApplicationFor whole settlements; depending on design and the availability of space, alsoapplicable in urban poor settlements

CostsHigh, due to substantial investment and operating costs

OperationsGenerally by municipal or private operators; in exceptional cases, operations bystable community organisations

InterfacesDischarging of pre-treated wastewater into a city-wide sewerage system possible

AdvantagesProtection of surface waters

DisadvantagesHigh investment and operating cost; high level of organisation required; largespace requirement

To be ConsideredRegular control and monitoring of effluent quality facilitates efficient operationsand protects against unforeseen discharges of under-purified effluents insurface waters

Assessment of Costs

The necessary investment costs forsetting up a non-mechanisedtreatment plant will include thepurchase or long-term lease of land,the labour costs for constructing theponds and the costs of materials(pipes, foils, etc.)

Operating costs are normally forregular maintenance and to theremoval of sludge at regular intervals.

It will generally be useful to checkwhether several decentralised plantsare more cost-efficient than just onelarger installation.

A particularly cost-efficient option canbe when a settled sewer system feedsinto a biological treatment plant,which uses soil infiltration.

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3.5 WASTEWATER


BIOLOGICAL TREATMENT PLANTS

operational and maintenancerequirements, it can be a viablealternative to other forms ofwastewater treatment.

The versatility of biological treatmentallows its application even in extremeclimates: it can be used in deserts, intropical areas, and also in highlands ormountainous areas with extreme frost.In addition, it is suitable for thetreatment of both lightly and highlycontaminated wastewater, and istolerant to the discharge of toxicsubstances and physical impacts orshocks (e.g. earth tremors).

The operations of biological treatmentplants do not require highly skilledpersonnel, or machinery, equipmentor energy.

A broad range of technical solutions isavailable for a wide variety of possibleuses. The basic prerequisites are forappropriately selected filteringmaterials and plants adjusted to thespecific climatic and otherenvironmental conditions of theirlocation. In addition, a sufficientsupply of water and nutrients will benecessary, as will pre-treatment toseparate and sediment solidwastewater components.

Application

Biological treatment plants can beapplied for various purposes. Theycan be used to treat both householdand commercial wastewater. Evenindustrial wastewater and effluentfrom landfill sites can be treated withthis technology.

Biological treatment is used to purifywastewater from one-family houses,housing estates and even whole cities.In the past, biological treatment wasmainly applied in industrialisedcountries. Currently, it is beingincreasingly used in countries of theSouth.

In urban poor settlements, biologicalwastewater treatment is still anexception. However, due to itsflexibility and relatively modest

Biological treatment plant for a housing estate (200 PE*) in Berlin (International Building Exhibition Block 6); the effluent is used forflushing toilets /108/

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3.5 WASTEWATER


Technical Solutions

The most important form of biologicaltreatment plants are installationsthrough which wastewater flows invertical and horizontal streams. Thewater flows through a 0.3 m - 1.0 mthick body of filtering substances thatcan consist of different materialsplanted with macrophytes (e.g.Phragmites Australis / reed).

The organic wastewater componentsare decomposed by both anaerobicand aerobic micro organisms, whichare supplied with oxygen and othermetabolic plant products through theplant roots. For pre-treatment inlarger systems, a multichamber pit,such as an “Emscher Well” (or Imhofftank) can be used. Treatment plantscan be constructed with just one basinor a number of basins in a row.

The basins should be sealed withconcrete, foil or clay. The inflowingwastewater should be distributedevenly at the inlet(s) in order to bestuse the filter volume and to avoidlocalised short-circuit currents.

The size of the plant determines thequality of treated water it produces.The technology is capable ofpurifying household wastewater to thestandard of the EU directive forwashing water, recycled irrigationwater or toilet flushing water. In thebody of the filtering material, allpathogenic germs (viruses, bacteriaand worm eggs) are permanentlyeliminated - a level of efficiency thatno conventional treatmenttechnology, with the exception ofmembrane (or fine mesh) technology,can achieve.

Dimensioning

In moderate climates, minimum require-ments for the discharge of householdwastewater with a specific surface of 5m2/PE* and a maximum hydraulic loadof 40 l/m2d can even be met in winter.In warmer climates, the maximum loadcan be significantly higher (in India,horizontally layered installations aredesigned on the basis of 1-2 m2/PE).

In installations with horizontal flows, awater gradient of about 1 % should beconsidered.

Filter materials should have a permeabi-lity of kf = 10-4 m/s. Filtering materialand layering should be selectedaccording to the type of wastewater tobe treated.

* PE - population equivalent: a unit of measurementreferring to a contaminated wastewater load of 60mg/l BOD

5per person per day

Biological treatment plant with a pre-treatment “Emscher well” and sludge separation for 60 PE in Grace, Auroville, Tamil Nadu inIndia; the effluent is used for irrigation purposes /109/

104

Operations

Installations based on vertical flowshave to be operated in a discontin-uous way; if colmation* occurs,operations will have to be suspendedfor some time. Treatment ponds withhorizontal flows can operate con-tinuously and can be more efficient.

In temperate climates, plants have tobe removed once a year, in springafter flowering. In tropical climates,this needs to be done twice a year,again after flowering. In addition tothe regular maintenance of pre-treatment installations, all thewastewater inlets, and treated wateroutlets should be checked andcleaned, as necessary, from time totime.

Colmation occurs only when pre-treatment does not function properly,or when inappropriate filteringmaterials have been selected.

The ponds should not be built inshady locations and should always besupplied with sufficient water. Macro-phytes have a high transpiration rate,a fact that will have to be considered,especially in hot and dry climates.

3.5 WASTEWATER


BIOLOGICAL TREATMENT PLANTS


Horizontally layered installations, inwhich wastewater is kept under thefilter material's surface, operate freefrom insects and bad smells. They cantherefore be established close toresidential buildings. Theirapplicability basically depends on theavailability of space and appropriatefilter materials. In steeply slopingterrain, terracing may be necessary toprovide the needed space. Construct-ion costs will thus be higher and maylimit their application in such cases.

When the amount of wastewater fallsoff seasonally, supplying the plantswith water during downtime will be adetermining factor in operations.

* Colmation - Clogging or blocking of the upper

layers of filter material resulting in blockages and a

slowdown of the purification processes and a

reduction of its permeability.

Auroville / IndiaWastewater Recycling

The city of Auroville is a new town,established 200 km South of Madras.In the first phase of development,reforestation and measures to preventsoil erosion were implemented. Asurban infrastructure was still missing,the new settlements neededautonomous water supplies andsanitation. To overcome watershortages during dry seasons, wellswere drilled, with depths of up to 100m, which were soon threatened withsalinisation. Protecting the mainaquifer, rainwater harvesting andwastewater recycling thus becameimportant priorities for securingsustainable water supply.

As early as 1994, a decentralisedtreatment plant for 85 PE, consistingof an “Emscher well” and a biologicaltreatment system, was planned andconstructed for the settlement ofGrace. After fermentation, sludge ismixed and composted with organichorticultural waste and used forlandscaping projects. The wastewatertreated is largely free of toxiccomponents, and is either used forirrigation directly, or is infiltrated intothe soil through “French drains”(rigoles).

Based on the same principle, foursmaller treatment plants were builtlater in Auroville. Pre-treatment isdone in 3-chamber fermentation pits,followed by biological treatment inbasins with a specific surface area of2 m2/PE. They were designed to beextendable in line with futuresettlement growth, with, in the firstphase, 12 - 35 PE.

Biological treatment plant in Grace, Auroville, Tamil Nadu, India: Filter basin /110/

105

Main FeaturesEnvironment-friendly and biological treatment of household, urban or industrialwastewater, with subsequent soil infiltration or discharge into surface waters.Multi-staged process comprising: pre-treatment to separate and ferment solidcomponents; absorption and adsorption of non-depositable wastewatercomponents in planted soil filters; almost complete elimination of pathogenicgerms

ApplicationFor individual housing areas, whole urban districts, urban poor settlement,commercial areas and factories

OperationsConstruction and operations by individuals, small-scale contractors orcommunity self-help possible; financing through small-scale loan programmespossible

InterfacesEmptying and disposal of sludge residues from pre-treatment pits bycommunity or private disposal companies

AdvantagesSimple technology, low maintenance requirements, free from smell nuisances,elimination of pathogenic germs, high levels of purification, versatility andflexibility; few restrictions with regard to the type of wastewater to be treated

DisadvantagesRelatively high investment costs, large space requirements, minimum watersupply necessary, high evaporation levels

To be ConsideredNeeds locations exposed to maximum sunshine, requires a high quality of pre-treatment and sealing of plants

3.5 WASTEWATER



Individuals and local craftsmen canuse the simple technology. Technicalassistance may be necessary inselecting appropriate locations andsoils. Smaller plants can be designed,constructed, coordinated andoperated through self-help. Localcraftsmen, supported by substantialcommunity self-help, can evenconstruct larger installations.

Biological treatment plants for wholeurban districts are communal facilitiesbut cannot be operated by individualsor self-help groups.

If public sector or municipal insti-tutions, or private enterprises are notwilling or interested in taking onoperations, they could possibly bedone by suitably stable communityorganisations that are sufficientlycapable and willing to acquire thenecessary skills. The financing ofoperating costs will, in any case, haveto be secured by user fees and othercontributions from the community.

Assessment of Costs

In Germany, construction costs forbiological treatment plants, dependingon their size, range from EUR 35 toEUR 200 /m2. In India, they cost USD30-130 US/m2. The main cost factorsare the availability of appropriate filtermaterial (e.g. sand or gravel); thecosts of sealing material, plants andother construction items are lesssignificant.

Operation costs are very low, as suchinstallations need very little energyand limited maintenance.

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RAINWATER4

108

Danger of flooding/111/

4.1 RAINWATER


Problems

Rainwater can pose problems whenthere is too much or too little of it.This is particularly true in urban poorsettlements, which are often inclimatically or topographically hazard-ous locations, e.g. on steep slopesthreatened by landslides, on loamysoil, in marshland with high ground-water levels, or in arid or desert areaswith inadequate water supply.

Too much rainwater

Rainwater can be a particular problemwhen it occurs seasonally in heavydownpours. If this is aggravated byadverse topographical conditions,such as steep slopes, low soil absorpt-ion capacities or high groundwaterlevels, it may have the followinghazardous impacts:• erosion of roads, public open

spaces or cultivable land;• undermining of roads, bank

reinforcements, bridges or houses;• landslides or mudslides; • local or extensive area flooding;• overflowing latrines, septic tanks

and treatment ponds;• increase of water-breeding insects; • increase of infections caused by

polluted water.

Too little rainwater

However, rainwater need not be ahazard: in dry and arid climates, it canbe a highly valuable asset. Inparticular, in peri-urban areas, whichoften suffer from inadequate watersupplies, rainwater can be used topartially cover household waterdemand. When rainwater is collectedbefore it can be contaminated bycontact with the ground, it can bereasonably clean. With some pre-treatment, it can be used for differentpurposes: • as potable water (when boiled for

sterilisation);• for washing, cleaning, dishwashing

and laundry;• for irrigation in horticulture and

agriculture.

Hazardous slopes and soilerosion

Due to hazardous locations of manyurban poor settlements, problems arenot only caused by too much or toolittle rainwater. Often, geologicalconditions can pose serious risks oflandslides and erosion:• steep or overhanging cliffs;• rifts or cracks in the ground,

particularly in earthquake-proneregions;

• loose rock or stone.

Landslide at a site adjacent to a steepslope /112/

Vulnerable housing beneath overhangingcliffs /113/

109

4.1 RAINWATER


Potentials

The main considerations for avoidinghazards from too much rainwater are:• controlled drainage of excess

water;• stabilisation of soil, buildings and

slopes against undermining water.

Where rainwater is scarce, possiblemeasures to conserve it can include:• using rainwater from roofs and

courtyard surfaces;• provision of rainwater collection

and storage containers.

Precautions can be taken to deal withthe potential problems of both ex-cesses and scarcities of rainwater atindividual household level, or bycommunity initiatives at neighbour-hood level, involving participation andself-help.

Possible Approaches

In the case of excessive rainwater,controlled drainage reduces soilerosion and avoids the occurrence ofstagnating water. Rainwater can bedrained in open or covered culverts.In addition, streets and roads can bedesigned in a way that drains off water(e.g. in form of so-called trough roads.Measures, such as terracing, erosionprotection trenches or ditches, slopestabilisation and planting trees andshrubs can also reduce erosion risks.Well-targeted residents' self-helpinitiatives can be promoted toimplement rainwater risk reductionmeasures.

Rainwater harvesting involves theselection and introduction of suitableapproaches to collecting, storing andcleaning rainwater, if possible incombination with greywater recycling.Traditionally, rainwater is harvestedfrom roofs of buildings, but it can also

Threat from loose rocks/114/

Main elements of rainwater management:• controlled drainage of rainwater from buildings and other

installations;• construction and maintenance of drainage canals;• road and street design enables temporary excess rainwater to drain

off;• connection of drains and culverts at settlement level to citywide or

regional drainage systems

Main elements of rainwater harvesting:• using available roofs and other suitable surfaces (e.g. paved

courtyards) for rainwater collection ;• construction of rainwater conduits or pipes (possibly with

intermediate interceptor tanks for sedimentation of solids) to waterstorage tanks or containers;

• construction or installation of appropriate rainwater storagecontainers above or beneath the ground

be collected from impermeableground surfaces (paved public spaces,rocky soil, arroyos or wadis, etc.).Collected rainwater can be storedabove ground and underground.Depending on its intended use,suitable filters may be needed.

Many rainwater harvesting techniquesare well suited for self-helpapplication. When accompanied byawareness campaigns and training inwater saving methods, rainwater

harvesting can make a significantcontribution to satisfying the waterneeds of residents of urban poorsettlements.

110

Different types of drainage channels/116

4.2 RAINWATER

DRAINAGE SYSTEMS

Technical Solutions

Depending on climatic conditions, amounts of rainwater and soil absorptioncapacities, different drainage solutions can be applied:

Drainage channels, gutters and culverts can be constructed parallel tostreets, or along their middle, or by profiling the street itself. They can also beindependent of roads and streets and run through open terrain. There are a largenumber of technical and engineering options for their design:• Simple, open or covered channels with different profiles for smaller streets

and pathways. These normally discharge into local sewer systems or largerainwater collector mains that carry rainwater from whole urban districts.

• “In channel channels”, which enable drainage of different amounts of wateraccording to seasonal variations of rainfall. During dry seasons, such channelscan also be used to discharge household greywater.

• Underground pipes and culverts, similar to sewer systems. • Covered culverts running underneath footpaths and stairways, which are

particularly suitable where space is scarce. The cover can be designed to bewalked on.

OPEN AND COVERED CULVERTS • TROUGH ROADS • RAINWATER RETENTION PONDS

Application

There is a broad range of well-provensolutions for rainwater and othersurface water drainage in urban poorsettlements.

In simple, but effective ways, thesesolutions provide efficient drainage forrainwater from often sudden heavytropical and sub-tropical downpours,and hence protect against potentiallymajor damage.

Effective rainwater drainage isessential to avoid uncontrolled waterdischarges, flooding and erosion,particularly in urban settlements,where large parts of the groundsurface are sealed by buildings,pavements or asphalting.

Functioning drainage will also beimportant in suburban and peri-urbanareas with fewer sealed surfaces, forkeeping streets and roads passableafter heavy rainfalls, and for limitinghygiene problems.

Simple rainwater culvert in Mali/115/

111

4.2 RAINWATER

DRAINAGE SYSTEMS

Dimensioning

The following factors will determinethe design and dimensioning ofrainwater and surface water drainagesystems:• the maximum amount of rainfall

per time interval;• the absorption capacity of soils;• the type of drain channel, culvert

or pipe (its material, bore smooth-ness, diameter, profile and form);

• the gradient and the resulting flowvelocity.

As a general rule, rainwater drainageand retention systems should not bedesigned for the maximum amount ofpossible rainfall, since, in most cases,this would lead to over-dimensioning.For drain profiles and diameters insystems with retention ponds, 3-6times the average water volume to bedrained during dry seasons is general-ly used as a basis for dimensioning.

Often, sewage canals are also used forrainwater drainage. They are frequent-ly designed for the maximum expect-ed amount of rainwater, and so theytend to fall dry over large parts of theyear. The average water and sewagevolumes to be carried can be wellbelow the capacities of the channels,and therefore insufficient flowvelocities are generated. As a con-sequence, deposits and sediment willbuild up over time, and this is oftenaggravated by residents using thechannels for refuse disposal. Whenrainfalls begin, the sediment andgarbage are washed through, but canblock lower parts of the system ortreatment plants, or can pollute therivers or lakes into which therainwater discharges.

Improved types of channels have beendeveloped especially to improve thefunctioning of these combinedwastewater and rainwater systems. Byincorporating smaller “in channelchannels”, sufficient flow velocitiescan be achieved, even for smallamounts of water.

An over-sized drainage canal during thedry season /118/

Staircase with culverts in Medellín,Colombia /117/

The drains can be cast from concrete,constructed from bricks or naturalstone, or assembled from ceramic (orsometimes plastic) half-pipes.

Trough roads are designed to serveas drainage canals for heavy rainfalls.Either the whole street (edged by highcurbs) or parts of it (with built-indrainage profiles) can be used. Withextremely heavy rainfall, high flowvelocities can occur. To avoid erosion,trough roads will have to be madewith solid surfaces of asphalt, concreteor stone.

Rainwater retention ponds are analternative to the big drains thatwould otherwise be needed to take inlarge amounts of rainwater. To dothis, ponds (sometimes in the form ofinfiltration basins with permeablebottoms) are built at appropriatelocations. The rest of the rainwaterdrainage system can therefore besmaller (and less expensive), withoutthe risk of flooding that small drainscan entail. This solution can beespecially appropriate for denselybuilt-up settlements, where sufficientspace to install such ponds is availablein areas above the settlement.

Depending on their type and usage(i.e. with or without infiltration to thesoil), retention ponds are constructedeither with waterproof (concrete orbrickwork) materials, or permeable(gravel) bottoms.

112

4.2 RAINWATER

DRAINAGE SYSTEMS

OPEN AND COVERED CULVERTS • TROUGH ROADS • RAINWATER RETENTION PONDS

Operations

Requirements for operations andmaintenance will differ according tothe type and construction of theinstalltions:

Drainage channels, gutters andculverts: To avoid blockages causedby garbage or sand sediments, it willbe useful to cover channels with, forexample, concrete slabs. In denselybuilt-up areas, covered channels canthen also be used as footpaths. Thecovering slabs should be heavyenough to prevent children moving orlifting them. On the other hand, theyshould be light enough to be removedwithout machinery by adults formaintenance, repair or clearingblockages.

To avoid refuse or other debris beingwashed into the system, all inletsshould be covered by a grille. Thisalso facilitates the removal of suchmaterial with a rake. Both open andcovered channels will have to becleaned at least once a year. In orderto make sure that the systemfunctions properly when rainfallsbegin, this should preferably be donebefore rainy seasons.

In tropical regions, drain trenches canfill up quickly with organic and othermaterial. In settlements at urbanfringes or in peri-urban areas, whereroads and streets are often unpaved,they can also silt up much faster thanin more consolidated inner urbanareas. Cleaning intervals will thus haveto be much shorter. For hygienereasons and to limit water-breedinginsects, accumulations of stagnatingwater should be avoided by providingchannels with adequate gradients.

Bulawayo, ZimbabweStreets as rainwater drains

In semi-arid south-westernZimbabwe, rainfall occurs only duringthe rainy seasons, when it can beextremely heavy. In the city ofBulawayo, all streets going downhillare constructed with W shapedprofiles. Their highest point is in themiddle, and they slope down towardsboth sides with a large gradient. Thestreet then tilts upwards to its edges.

In heavy downpours, the water flowsoutwards from the middle to bothsides. Water from sidewalks and curbsdischarges inwards. Both rainwaterstreams merge in the right and leftlow points and then flow downhill.Both the street and the sidewalksthus remain passable even duringheavy torrential rains. A particularadvantage of this solution is its lowcost, since no additional rainwaterdrainage is needed.

The disadvantages are at inter-sections, where crossing traffic mustsometimes go through up to 20 cmdeep rainwater streams. The arrange-ment also requires substantial space.

Trough roads are primarily for trafficand basically will have to be operatedand maintained like other roads. Toensure their drainage capabilities,road surfaces should be kept intact.The disposal of refuse, gravel or soilon them should be avoided, as shouldthe long-term parking of vehicles.

Rainwater retention ponds tend tosilt up. Large amounts of sand, treebranches or garbage can accumulateinside the pond, particularly afterheavy rainfalls. They will thereforehave to be cleaned after every majordownpour, in order to maintain theircapacities.


Because all rainwater drainage andretention installations should not besized to take maximum amounts ofpossible rainwater, extremely heavyrainfalls may lead to short-termflooding.

In mixed sewage and rainwatersystems, contaminated wastewater canflood adjacent areas during shortphases of overload. But as this willusually occur during periods ofabundant rainfall, i.e. water supply,the wastewater will be quickly dilutedand cleaned by new water: such short-term adverse effects can be acceptablein many cases.

113

A small culvert running alongside a profiled street /119/

4.2 RAINWATER

DRAINAGE SYSTEMS

Main FeaturesControlled drainage of surface waterby culverts, larger channels ortrough roads; possibly complement-ed by retention ponds

ApplicationSettlements with sealed groundsurfaces and protection againsterosion

CostsLimited construction and materialcosts, if carried out throughcommunity self-help

OperationsBy individual self-help on privateproperty only; otherwise throughcommunity self-help at settlement orneighbourhood level

Interfaces Discharge of collected rainwater intomunicipal systems

AdvantagesControlled drainage prevents majorflooding and erosion damage

DisadvantagesBlocking of channels and retentionponds by refuse and sand; regularmaintenance and cleaning isindispensable

To be ConsideredBecause systems should not be sizedfor the maximum amount of possiblerainwater, heavy rainfalls may lead toshort-term flooding.


In most cases, all settlement residentswill benefit from improved rainwaterdrainage, and their living conditionscan improve considerably. Theconstruction of such systems does notpose any major technological orfinancial challenges, and is thereforewell suited for community initiatives.If it is well organised at settlement orneighbourhood level, most necessaryworks can be done through self-help.However, it may be necessary tocontract specialised construction firmswhen there are difficult soilconditions, e.g. rocky subsoil.

Most maintenance and repair workcan also be organised and executedthrough self-help at settlement orneighbourhood level.

Assessment of Costs

Construction costs will largely dependon the type of drainage systemselected, and on the kind of materialrequired.

Depending on soil and subsoilconditions, expected rainwatervolumes and other local specifics,system components and constructioncan either be relatively simple orrequire more sophisticated (andcostly) technical solutions.

If construction is done through self-help, the main costs will be formaterials.

114

Slopes threatened by erosion inHonduras /120/

Building drainage/121/

Terracing in Medellín, Columbia/122/

4.3 RAINWATER

EROSION PROTECTION

EROSION PROTECTION AND SLOPE STABILISATION

Application

Urban poor settlements often developin disadvantageous locations, such assteep mountainsides, slopesthreatened by landslides or flood-prone areas, and so they are oftenseriously affected by erosionproblems.

Preventing and repairing erosiondamage is often a major challenge forwaste management projects. In manycases, erosion prevention measurescomplements rainwater drainage, andare indispensable.

Technical Solutions

As a general rule, such measures protect against soil slippage or erosion causedby climatic effects (above all, from water and solar radiation), and help preventdamage to built works (houses, streets and roads, community facilities etc.) fromlandslides, subsidence, flooding or undermining. The following mainly preventivesolutions can be applied in urban poor settlements:

• Building drainage: Drainage canprotect buildings from beingundermined by water. Trenchesfilled with coarse gravel and withan outlet to the ground, are dugalongside the building's walls.Water spilling off roofs, or ac-cumulating close to the building,is thus effectively carried away. Itwill be important to preventdrainage trenches becomingclogged with debris over time,reducing drainage efficiency.Inserting a horizontal barrier (e.g.a layer of tar paper) can preventdrainage trenches silting up. Often, it will be sufficient to simplypave the ground alongside thebuilding (e.g. with stone or con-crete slabs), sloping away from thewalls. Water spilling from the roofwill be diverted from the base ofthe walls and thus be preventedfrom undermining the building.

• Terracing: Terracing risk-proneslopes is one of the most effectiveways to reduce the flow velocitiesof rainwater and other surfacewater. For this purpose, low wallsare constructed along the contourlines of the terrain and back filledwith earth. Where sufficient spaceis available, terraces can beplanted with grass, shrubs andtrees to prevent the earth washingaway and to further reduce watervelocities.During the initial stages, whenterraces are not yet protected byvegetation, mesh-like wattle, madefrom twigs and branches, canprevent soil washing away. Indensely built-up areas, it may bedifficult to build the terracingsurfaces flatly enough to preventlandslides.

115

Retaining walls erected in the context ofa slum upgrading project /124/

Slope stabilisation in Inner Mongolia,China /125/

4.3 RAINWATER

EROSION PROTECTION

Rehabilitation after erosion damage/123/

• Stabilizing erosion gullies:Erosion gullies often form ineroding soils. Rainwater flows areconfined within them, resulting inhigh flow velocities. Erosiongullies are thus extended anddeepened. When they cannot becompletely filled in, small barragesshould be built across them toreduce flow velocities and topromote sedimentation. These canbe made from wattle, earth or wirepackages filled with stones.

• Bank reinforcement: Manyurban poor settlements are inflood-prone waterfront areas. Theyare therefore exposed to highrisks from flooding and erosion,particularly during rainy seasons.Water banks can be protected byconstructing jetty walls, river damsor weirs (to slow water flows) orby stabilizing or reinforcing thebanks themselves. Bankreinforcements mainly prevent soilwashing away or the bank beingundermined. In many cases, thiscan be achieved by tree planting.Trees with deep roots that grow inwater or marshland or mangrovesare usually appropriate. Speciesshould be selected according toregion and climate.

• Retaining walls: The construct-ion of retaining walls will often bethe only viable, but usually verycost-intensive, option for protect-ing slopes against landslides,particularly in densely built-upareas in mountainous or hillyareas.It will be important to allow forsufficient openings in the walls forthe discharge of built-up waterand to avoid erosion andundermining.Retaining walls can either be madeof concrete or bricks orstonework. Building materials,machinery and labour can makeretaining walls expensive.However, they may be the onlypossibility for protection againstlandslides, particularly in denselypopulated settlements.

116


The success of erosion protectionmeasures in urban poor settlementslargely depends on the motivation andinitiative of residents and localadministrations. Protection measuresshould not be beyond the technical,financial and spatial resources of bothresidents and local administrations.

But in settlements affected by erosionproblems, the effort needed toimplement protection measures willoften be too high and, in addition,may not be financially feasible.

Operations and maintenance oferosion protection installationsrequire a high level of organisationand community ownership, whichcannot always be guaranteed in urbanpoor settlements.

Medellin, ColombiaErosion Protection Measuresin the Context of an UrbanUpgrading Programme(PRIMED)*In Medellin, the second largest city ofColombia, about 250,000 people, orroughly 14% of the city's total popu-lation, live in about 104 informalsettlements, so-called barrios sub-normales, which have developed onthe steep slopes of the mountainssurrounding the city. Most of theseslopes are highly threatened byerosion; heavy rainfalls usually causelandslides and avalanches of fallingrocks, endangering the lives andproperty of residents.

Within the framework of an integrat-ed urban upgrading programme,financially supported by GermanFinancial Assistance (KfW) since thebeginning of the 1990s, compre-hensive measures were implementedto stabilise eroding slopes. Thesemeasures included the paving ofstreets (either with concrete orasphalt, depending on the loadbearing capacities of the ground), theconstruction of footpaths and stair-ways (where street building was notpossible without implementing ex-pensive slope stabilisation measures),building retaining walls, reforestationmeasures and regulating small creeks.

With the active participation of resi-dents, numerous smaller stairwaysand drainage channels were built, andresidential areas were made greenerby planting trees and shrubs. In orderto ensure proper maintenance of theerosion protection structures, com-prehensive awareness campaigns andtraining activities were put into effect.

* Programa Integral de Mejoramiento deBarrios Subnormales en Medellín

4.3 RAINWATER

EROSION PROTECTION

EROSION PROTECTION AND SLOPE STABILISATION

Dimensioning

The type and scope of necessaryerosion protection measures willdepend on the volume and intensityof rainfall, soil conditions and ontopographical and geological specifics(slope gradients, rock stratificationetc.).

The design of technically moresophisticated solutions (such as slopestabilisation or bank reinforcement)requires special engineering know-how, and in cases, detailedinvestigations and calculations.

Less complicated small-scale solutions(e.g. building drainage or terracing)can often be based on experiencegained from local “trial-and-error”undertakings.

Operations

Erosion protection is an ongoingprocess, requiring all year roundattention. All installations will have tobe regularly maintained and lookedafter. Potential dangers will have to beavoided and improvements should bemade continually (e.g. planting oftrees, repair works).

Slope stabilisation in Medellín, Columbia/126/

117

4.3 RAINWATER

EROSION PROTECTION

Main FeaturesWell-targeted construction measures or solid structures to slow down waterflows in order to prevent soil washing away or being undermined, and toprevent landslides and soil erosion

ApplicationFor topographically disadvantaged locations on steep slopes, river banks, etc.

CostsDepending on type of construction measures necessary: often low costs forconstruction, materials and labour; more complex slope stabilisation or bankreinforcement measures can be very expensive

OperationsIndividual self-help initiatives possible for smaller measures on private land;larger-scale measures can be undertaken by community groups or associations;more complex and technically challenging measures require specialisedconstruction firms and external financing will be necessary

InterfacesFor larger construction measures, support from municipal or other publicinstitutions will be needed, since collected water will usually have to bedischarged into municipal or other public networks

AdvantagesErosion protection measures can, in the main, be implemented by residentswhen they receive adequate financial support

DisadvantagesSuccessful measures need a high level of community organisation andownership, and regular year-round maintenance and care

To be ConsideredRecurring necessities:• All structures must be well-maintained.• Adverse risks resulting from clearing of trees and shrubs, or from building

activities should be avoided.• Erosion control structures should be improved by planting trees, terracing

and drainage


Most of the measures described hererequire only limited external resourcesfor their implementation; they are,however, labour-intensive. Givensufficient resident mobilisation andorganisation, they are well suited tobe undertaken through self-helpinitiatives. As most of the requiredwork is beyond the scope of individualinitiatives, a functioning community,which could organise self-help orneighbourhood groups, will beneeded. Imparting technical know-how and raising awareness of theadvantages of erosion protectioncould possibly be another function ofsuch groups.

Residents of urban poor settlements,who are more concerned withsecuring their livelihood, often givelittle attention to erosion protection.Therefore the allocation of energy,time and money needed for it isfrequently not forthcoming.

Assessment of Costs

As mentioned before, many erosionprotection measures can be realisedthrough self-help. However, larger-scale construction measures will oftenrequire the acquisition of specialbuilding materials. This can possiblybe financed by communitycontributions, small-scale loans ormunicipal subsidies.

The more risk-prone the location, themore expensive the erosionprotection measures will be.

118

Application

In many cases, households in urbanpoor settlements are not connected tocentralised (municipal) water supplynetworks. Residents must thereforeget water from faraway wells or publicfaucets, or buy it at high cost fromwater tanker trucks or other privateproviders.

In regions with sufficient rainfall,collecting and storing rainwater can bea simple, relatively cheap way to pro-vide for at least part of a household'swater demands (e.g. for washinglaundry, toilet flushing, cleaning,irrigation of gardens). Collected water,if it is sufficiently clean, can even beused for drinking when properlyboiled.

RAINWATER HARVESTING AT HOUSEHOLD LEVEL • STORAGE CONTAINERS ABOVE AND BELOWGROUND

4.4 RAINWATER

RAINWATER HARVESTING

Technical Solutions

Roofs and paved or water resistantground surfaces (asphalt, concrete,tiles or stone slabs, stamped clay etc.)can be used for harvestingrainwater at household level.

Rainwater is commonly harvestedfrom roofs, where water will generallybe cleaner. Depending on the shapeof the roof, water can be collected anddischarged from one or more of itssides.

When rainwater is harvested fromcourtyards or other ground surfaces, itwill be necessary to ensure that:• the collecting surface is

impermeable; • the surface is sufficiently sloped in

one direction;• a collecting pipe or channel is

installed at the lower end;• the collecting pipes or channels

have sufficient falls to storagetanks or containers;

• if necessary a sieve or interceptorshould be installed for debris andmaterial such as sand.

Storage tanks or containers will beneeded for collecting and storingrainwater. These are normallyinstalled aboveground, but can also bebuilt underground. In some countries,underground rainwater cisterns havebeen a traditional solution forcenturies.

Rainwater storage tanks can be madein many forms and materials, and canrange from the inexpensive andsimple to the sophisticated andexpensive. The simplest are well-cleaned used oil barrels. Common andtraditional materials for manufacturingwater storage tanks are corrugatediron sheets, reinforced concrete andreinforced brickwork. In industrialisedcountries, they are injection mouldedfrom plastics or assembled fromprefabricated concrete segments.

Harvesting rainwater from roofs /127/

Brickwork rainwater storage tank /129/

Rainwater storage in barrels/128/

119

4.4 RAINWATER


Dimensioning

Roofs with one or more slopingsurfaces are best-suited for rainwaterharvesting. As a general rule, eavesgutters should have a minimumgradient of 1% (3% is better).

Flat roofs can also be used for rain-water harvesting when they are builtwith perimeter upstands and acontrolled water outlet, or outlets.

Not all roofing materials are equallysuited for rainwater harvesting. Claytiles, corrugated iron and aluminiumsheets are particularly appropriatematerials. Grass roofs can also beused, but collecting and discharging ofwater will be more difficult because oftheir irregularities.

The selection of constructionmaterials and the sizes of rainwaterstorage containers or tanks will haveto take account of the followingdetermining factors:• volume, distribution and seasonal

variation of annual rainfall; • duration of dry periods, in

particular in years of drought;• area of available collection

surfaces;• number of persons using the

collected water; • intended use of collected water

(for drinking water, laundry andcleaning, washing, irrigation, etc.);

• locally available technical skills formanufacturing water tanks;

• available construction materials;• necessary investment costs and

their affordability;• life span of tanks;• maintenance requirements;

• pollution avoidance measures (e.g.for reservoirs used for potentialdrinking water);

• safety aspects (e.g. for accessibleabove ground storage tanks).

In arid regions where water isharvestable from only a few rainfalls,storage tanks should be large enoughto take in the total annualprecipitation.

In tropical or sub-tropical regionswhere a single heavy downpourproduces more water than can besensibly stored, tanks or containersizes should be determined byhouseholds' annual waterconsumption.

In regions with regular and reliablerainfall, storage capacity can be basedon either monthly water demands ormonthly precipitation volumes.

Depending on how full they are,substantial water pressure can occurin large storage tanks, and this shouldbe taken into consideration in theirfabrication. Above ground tanksshould therefore only be designedand built by experienced skilledpersons.

Water tanks built of brickwork orconcrete will never be totally leak-proof. Their insides will thereforehave to be coated with sealant, suchas waterproof plastic paint (e.g.swimming pool coating). Tanksaboveground should have an outletnear their lowest point for theremoval of sediments from time totime. The outlet for usable watershould be about 10-15cm above thelowest level, in order to avoid possiblesoiling with sludge.

Water pressure is less of a problem inunderground water tanks, since thesurrounding earth absorbs most of itsforce: they will therefore need lessreinforcement. A sufficiently largemanhole will be required for cleaningand inspection. Water is usually takenout with a hand operated ormotorised pump.

Operations

In order to harvest the cleanestpossible rainwater, the followingprecautions should be taken:• Branches of close by trees should

not reach over roof surfaces fromwhich water is taken.

• Before the beginning of the rainyseason, all collection surfaces,gutters and storage containersshould be thoroughly cleaned.

• The water collecting during thefirst moments of rainfalls containsthe most dirt and should not beharvested, but be diverted fromcontainers for about one minute.For this purpose, so-called“rainwater separators” can beused. Incoming water has to passacross a gap in the pipe or chan-nel leading from the collectionsurface to the container inlet:water will only be able to bridgethis gap when it flows sufficientlyfast. The first water that arriveshere during a rainfall will bemoving too slowly to cross thegap; therefore it will not be able toreach the storage container, andinstead will discharge, togetherwith the dirt it is carrying, throughthe gap to the ground.

120


Collecting and storing rainwater doesnot usually require major investmentsand is well-known and traditional inmany regions of the world. Mostcomponents of rainwater harvestingsystems can be installed through self-help.

In urban poor settlements, wherespace for large individual storagecontainers is often scarce andindividual solutions may not beaffordable to residents, community

Water storage tank from reinforced sythetic resin in Botswana /130/


Rainwater can be harvested effectivelywhen rainfalls occur not only duringshort seasons, but over the wholeyear. When there are only a few heavydownpours per year, they must betaken advantage of to the maximumpossible extent. Large collectionsurface areas, collecting pipes andstorage containers will therefore beneeded. The investments required forthem may not be affordable for poortarget groups.

4.4 RAINWATER


RAINWATER HARVESTING AT HOUSEHOLD LEVEL • STORAGE CONTAINERS ABOVE AND BELOWGROUND

BotswanaLocally manufactured rainwater storage tanks

In Botswana, a local firm markets a special type of rainwater storage tank. The firmrecycles waste from another local enterprise that produces large water pipes fromfibre-glass reinforced synthetic resin. Reject pipes (with diameters up to 2 m and wallthicknesses of up to 3 cm) that have not passed pressure tests, are cut intosegments, and openings for manholes are made in them. They are then closed atboth ends with plates, also made from fibre-glass reinforced synthetic resin.

They are used, vertically or horizontally, to store rainwater from private orcommercial roof surfaces in single tank or joint tank systems. Due to their thickwalls, the tanks are very stable and solid, and free from corrosion. They can beinstalled without foundations or further reinforcement. One disadvantage is theirweight, and equipment is needed to transport and install them.

For collecting rainwater from groundsurfaces, an interceptor basin forseparating sediments should beinstalled above the (usuallyunderground) storage tank. The basinshould be large enough to allow theincoming water to settle and its solidcomponents to sediment. Collectionsurfaces should be kept clean of oil(e.g. motor oil from vehicles) and anychemical residuals (e.g. fertiliser,herbicides, fungicides, detergents,etc.). Other possible watercontaminants (e.g. bird or otheranimal droppings) should also betaken into account.

To avoid leakages, tanks should bechecked for the early signs of cracks atleast once per year, preferably beforethe beginning of the rainy season.Sediment sludge should be removedfrom the tank before this is done, andin any case, from time to time, asmentioned earlier. This will maintainthe tank's storage capacity and hinderfermentation processes.

121

4.4 RAINWATER


Main FeaturesHarvesting of rainwater from roofs and ground surfaces; storage in tanks orreservoirs for use as drinking water (boiled), for laundry, cleaning and/orirrigation

ApplicationFor all buildings with impermeable slopping roofs and paved ground surfaces;possible application at household level and for small-scale enterprises.

CostsReasonable; mainly depends on the required sizes of containers or tanks; wherewater supply is expensive, significant water cost savings are possible

OperationsIndividual self-help initiatives on private land; larger installations by communityor neighbourhood groups

InterfacesNone

AdvantagesGenerally technically simple and low-cost solution

DisadvantagesIf rainfall is limited to short seasons with only a few heavy downpours per year,large collection installations and containers will be needed for storing waterover longer periods of time. The required investments may not be affordablefor individual households in poor areas

To be ConsideredTo obtain the cleanest possible water, collection surfaces and storage tanksmust be regularly cleaned; limited usage as drinking water is possible (but onlyafter boiling).

Due to high water pressure that can occur in tanks, above ground tanks shouldonly be designed and built by technically skilled persons.

In order to avoid fermentation processes, sediment sludge has to be regularlyremoved from tanks, e.g. before each rainy season.

installations can be a viable alternative.In such systems, rainwater collectedby a number of households is storedin a large joint reservoir. However,this requires a high level of com-munity organisation and ownership,and will need to be promoted andsupported by community associationsor local governments.

Assessment of Costs

Compared to the total constructioncosts of a house, the additionalinvestments needed for collecting andstoring rainwater from roofs orgroundwater surfaces will not be veryhigh. The construction of anappropriate storage tank will usuallythe main cost item. The volume ofwater to be stored will therefore bethe main factor in determininginvestment costs. On the other hand,when water supply is expensive, e.g.when water has to be purchased fromtanker trucks, rainwater harvesting canprovide significant cost savings.

123

ANNEX

• Solid Waste- Checklists- Tables- Design Criteria and References

• Wastewater- Checklists- Tables- Design Criteria and References

• Literature

• Photo and Illustration Credits

124

ANNEX

SOLID WASTE

Transport Option Individual Manual Push-cart Donkey Cart Collector Truck / Municipal Operator

Important Factors

1. Requirements:

- procurement - not necessary - necessary - necessary - necessary

- street network - foot paths sufficient, - foot paths sufficient, - foot paths necessary - street networkstairways possible no stairways necessary

- topography - low relevance - difficult in areas - application difficult - not applicable inwith steep slopes in areas with steep areas with steep

slopes slopes

2. System features:

- procurement / - - locally possible - locally possible - must be imported in manufacturing / simple (carts) most cases

- material - - locally available - locally available - must be imported

- operations and - - low requirements - animal husbandry - medium requirementsmaintenance must be possible

- procurement costs - - very low - low - medium to high

- operating costs - possibly wages - possibly wages; - wages and costs - high (fuel /otherwise low for fodder; repairs)

otherwise low

3. Risks of - low to medium - low to medium - low to medium - low to mediumcontamination

4. Down times: - none - low - low - medium

5. Other: - well suited for - allows transport - improvement on - requires operations byareas with difficult of larger waste manual pushcarts professional topographical volumes in as larger transport (municipal)conditions densely built-up distances are possible service providers

- appropriate - intermediate - intermediate - intermediatefor densely storage or transfer storage or transfer storage or transferbuilt-up areas stations necessary stations necessary not necessary

- intermediate storage or transferstations necessary

ASSESSMENT OF SOLID WASTE TRANSPORT OPTIONS

125

Storage option Unorganised Storage Organised Storage ContainersArea (Dumping) Area (walled or fenced)

Important Factors

1. Requirements:- space - needs sufficient space - needs sufficient space - needs sufficient space

needed (>100m2) (>30m2)

- accessibility - must be accessible - must be accessible - must be accessiblefor collector trucks for collector trucks for collector trucks

2. System features:- construction - - locally possible - often must be imported

/ manufacturing

- material - - locally available - often must be imported

- operations and - regular - regular - regular cleaning ofmaintenance cleaning necessary cleaning necessary container site necessary

- investment costs - none - low - medium

- operating costs - none - very low - very low

3. Risk of contamination: - very high; breeding ground - very high; breeding ground - high, when not adequatelyfor vermin (rats, flies, etc.) for vermin (rats, flies, etc.) covered and irregularly

emptied

- contents scattered - contents scattered - soiling of site in whenby animals and the wind by animals and the wind container has insufficent

capacity and when childrenor smaller people cannnot reach up to the container

4. Down times: - none - none - only in the case of irregularor insufficient emptying

5. Other - should be avoided, - significant improvement - containers should be as nuisance to residents on unorganised designed so that childrenin the vicinity is high storage and dumping and smaller people can

also use them

- very precarious hygiene - regular collection and - regular collection andaspects, transport needed in transport needed to

order to avoid avoid nuisance and hazardscontamination similar to those of

unorganised collection- risks of flooding and areas

dispersion of waste during rainy seasons

ANNEX

SOLID WASTE

ASSESSMENT OF INTERMEDIATE STORAGE AREAS AND TRANSFER STATIONS

126

A. Raw material

• What types of waste material will be collected?

For each type:• From which places is the waste material collected or purchased?• What will be the monthly amount of collected waste?• What is the average distance to drive for collection or purchase?• What means of transport are required?• What is the waste material quality?• Is the material free of charge or must something be paid for the material?• Do people bring the waste? For what price?

B. Waste handling technologies and administration

General set-up:• Where will the waste be accumulated/stored?• What type of premises are needed?• What type of infrastructure is required at the premises?• What will be the total investment for establishing the infrastructure?• How many people will be employed and what organisational structure will be

needed?

For each type of waste:• What is the quality of the entering material?• What type of up-grading process will be applied?• What type of machinery is necessary?• How many labourers are needed for up-grading?• What will be their productivity?• What is consumed during processing (energy, fuel, lubricants, water, ets.)?• What investment will be required to buy the required machinery, means of transport,

office equipment, etc.?• What will be the quality of the products to be marketed?• What will be the operational costs?

C. Marketing of products

For each product:• Who are the customers for the product?• Where are the customers located?• What is the market price of the product?• What is the transport distance and what are the transport costs?• What will be the monthly amount to be shipped and sold?• What means of transport are needed?• What will be the operational net profit of the total operation?

CHECKLIST TO ASSIST IN THE LAYOUT OF PROJECTS IN THE RECYCLING SECTOR

ANNEX

SOLID WASTE

127

ANNEX

SOLID WASTE

A. Production Process

• Application of processes- Feed preparation?- Main process?- Final handling, e.g. canning, packaging, storage, etc.?- Auxiliary machinery?

• Location of manufacturers/suppliers of the machinery- Locally?- In neighbouring countries?- Overseas?- Do they provide service, maintenance and spare parts?

• Purchase conditions of equipment- Price of equipment?- Transport costs to premises?- Import taxes?- Price of spare parts including tax and transport?- Lifetime of machinery and guarantees?

• Operation characteristics- Manual, semi-mechanised or automatic operation?- Batchwise or continuous operation?- Is operation of low or high productivity?- Energy intensive?- Noisy and polluting?- Risky for the worker’s health?- Generates reasonable amounts of waste and residues?- Generally environmental friendly or unfriendly?

B. Economic factors

• Labour market- Availability of skilled labour?- Level of wages aud related labour costs?- Availability of technical assistance by local reseach and tenchnology institutions?

• Capital market- Level of self-financing by the entrepreneur?- Level of interest rates?- Availability of favourable investment loans?- Existence of government support schemes?

CHECKLIST TO ASSIST IN THE SELECTION OF APPROPRIATE PROCESSES AND MACHINERY

128

• Description and history of company- How and what the company is?- Status of project/company?- Key goals and objectives?

• Product and Services- What the product or service is?- How it works?- What it is for?- Proprietary advantages?

• Markets- Who the prospective customers are?- How many customers there are?- Market growth rate?- Competitors? - Industry trends?- Estimated market share?

• Operations- How the product or service will be manufactured/provided?- Facilities/equipment?- Special processes?- Labour skills needed?

• Channels of distribution- How the product or service will be distributed?- Means of transport?- Advertising and marketing?

• Management- Who will do what?- Staff qualifications?- Availability of skilled labour?

• Financial prospects- Investment costs?- Capital costs?- Operational costs?- Monthly turnover?- Prospected yearly revenues?- Tax, social and legal costs?- Cash flow analysis (one year)?- Feasibility study?

• Sources and application of funds- Present needs? - Future needs?- Own funds?- Required loans or grants?

ANNEX

SOLID WASTE

EXAMPLE OF A BUSINESS PLAN FOR REFUSE RECYCLING

129

OVERVIEW AND ASSESSMENT OF DIFFERENT SANITATION OPTIONS

ANNEX

WASTEWATER

Total Construction Operating Land O & M Degree of PossibleInitial Labour Costs Requirements Skill Treatment ParticipationCosts Required as Level

Fraction ofTotal cost

On-Site Ssystems

VIP Latrines low high low moderate (if low low users,superstructure is (unsuitable community,moved when pit with high governmentis full) water table)

Double low to high low low low moderate users,

Vault Above moderate community,Ground governmentLatrines

Batch low high low low low moderate users,

Composting (unsuitable community,Latrines with high government

water table)

Continuous moderate moderate low low low moderate users,

Composting (unsuitable community,Latrines with high government

water table)

On-Site Liquid Disposal with Offsite Solids Disposal

Pour Flush low to moderate low moderate low low users,

Toilet with moderate (unsuitable community,Soakaway with high government

water table)

Pour Flush moderate moderate low moderate low moderate community,

Toilet with governmentSeptic Tank

Cistern moderate to moderate high high low moderate community,

Flush Toilet high governmentwith SepticTank

Off-Site Disposal

Vault or Pit low to high moderate low low Depends on users,

Toilet with moderate final community,Cartage disposal government

Bucket low high moderate low low Depends on users,Latrine final community,

disposal government

Water Borne Sewage Collection

Simplified moderate moderate low moderate low none government

Solids Free moderate moderate moderate moderate low none community,government

Condominial low to high low low low none users,moderate community,

government

Conventional high moderate high moderate high none government

130

ANNEX

WASTEWATER

ASSESSMENT OF DRAINAGE OPTIONS (SURFACE WATER)

Drainage Option Simple Earth Trench Reinforced Trench Covered Paved Road or Canal or Canal Culvert / Canal (Trough Road)

1. Requirements:

- topography - low slopes - low slopes - low slopes - low slopes(<1%) (<2%) (<2%)

2. System Features:

- construction - simple - with - advisory assistance - requires - advisory assistanceadvisory assistance necessary skilled labour necessary

- material - locally available - importing - generally, has to bematerial (e.g. cement) may be be importedcan be used necessary

- operations and - high effort for - high effort for - medium effort for - low effort formaintenance cleaning cleaning cleaning cleaning

- construction costs - low - medium to high - very high - included inroad constructioncosts

- operating costs - high, when contracted - high, when contracted - medium - included inout (payment of out (payment of road maintenancewages) wages) costs

131

ANNEX

WASTEWATER

COSTS OF SANITATION OPTIONS PER HOUSEHOLD (1990 PRICES)

Sanitation Option Costs(USD)

Twin-pit pour-flush latrine 75-150

VIP-latrine 68-175

Shallow sewerage 100-325

Small-bore sewerage 150-500

Conventional septic tank 200-600

Conventional sewerage 600-1,200

132

ANNEX

WASTEWATER

Faeces components Europe and North Developing Countries Developing CountriesAmerica (rural) (urban)

Assumed weight 150 250 350of adult faeces [g/d]

Assumed weight 1.2 1,2 1,2of adult urine [kg/d]

Estimate water components 75 80 85of faeces [%]

In wet faeces [mg/g]a 96 77 58

Faeces per adult [g/d] 14.4 19.3 20.3

Urine per adult [g/d] 10.3 10.3 10.3

Total excrements per adult 24.7 29.6 30.6[g/d]

Anal cleaning material per 3.5c 3.0d 2.0dadult [Cg/d]

BOD5-concentration [mg/l]b 18.8 21.7 21.7

Note: This table provides general orientation only. The data in it should be verified against concrete evidence and analysis. a. Calculated on the assumption that the BOD5 per weighed dry faeces unit is constant.b. Based on the assumption, that 1.5 litres per adult per day are produced.c. Von Laak (1974).

Components of Human Excrements in Different Regions

CONTAMINATED LOAD OF WASTEWATER

Country or Region BOD5 per-capita-Concentration in wastewater (g/d)

Brazil (Sao Paulo) 50France (rural) 24-34India 30-55Kenya 23-40Nigeria 54Southeast Asia 43UK 50-59US 45-78Zambia 36

Note: These data were calculated by measuring BOD5-concentrations in raw sewage and multiplying it by daily water consumption perinhabitant. The results only provide a rough orientation, since urban wastewater con contain considerable amounts of commercial andindustrial waste.

BOD5 Concentration in Wastewater in Different Countries

133

ANNEX

WASTEWATER

Type of Wastewater maximum contamination with:

COD NH4-N Helminth eggs Faecal coliforms(mg/l) (mg/l) (No./l) (No./100ml)

Liquid Wastewater

Quality of effluent for discharging into receiving water:

• into to seasonally flowing < 300-600 10-30 <2-5 <104

watercourses (wadis, arroyos)• into always flowing rivers <600-1.200 20-50 <10 <105

or the sea

Quality of effluentfor recycling1, 2:

• limited irrigation n.c. 1) <1 <105

• irrigation for growing vegetables n.c. 1) <1 <103

Sludge3

Use in agriculture n.c. n.k. <3-8/g TS low risk when, max. no. of Helminth-eggsis not exceeded

n.c. = not critical

1) Nitrogen load should not exceed 100-200 kg per/ha per year.2) WHO 19893) Xenthoulis and Strauss 1991

PROPOSED QUALITY STANDARDS FOR WASTEWATER EFFLUENT AND SLUDGE

134

ANNEX

WASTEWATER

SCHEMATIC SKETCH OF A WASTEWATER TREATMENT PLANT AT SETTLEMENT LEVEL

135

ANNEX

LITERATURE

(1) Jaradat I.S.Y.: Municipal SolidWaste Management in Jordan,Aqaba: International Institute forInfrastructural, Hydraulic andEnvironmental Engineering,University of Delft, TheNetherlands, 1999

(2) Vest H., Jantsch F.:Untersuchung des Aufkommensfester Abfälle in Koulikoro, Mali;GTZ, 1999

(3) Seghezzo L., Galdeano R.,Montiel E., Schindler M.:Integrated Waste Management inArgentina; Warmer Bulletin No.71; March 2000, p. 18-19

(4) Warmer Bulletin No. 69

(5) Constantinou D.: Municipal SolidWaste Management in Cyprus;Warmer Bulletin No. 53, March1997, p. 20-21

(6) Hassan M.N.: Waste Managementin Malaysia;Warmer Bulletin No. 51,November 1996, p. 18-19

(7) N.N.: MSW in The USA; WarmerBulletin No. 67; Novemver 1999, p.8-9

(8) Gupta S, Kansal A.: Solid WasteManagement in Indian Cities;Warmer Bulletin No. 60, May 1998,p. 4-6

Austin L.M., van Vuuren S.J.: CaseStudy: Urine Diversion Technology 25th WEDC Conference, Addis Ababa,Ethiopia 1999

Austin L.M., van Vuuren S.J.:Technical Aspects of EcologicalSanitation. Department of CivilEngineering, University of Pretoria,South Africa 1998

Baumann W., Karpe H.J.:Wastewater Treatment and ExcretaDisposal in Developing Countries.Institute of Environmental Protection(INFU) Dortmund, March 1980

Bark K. et al. (Gutachterteam):Modellhafte nachhaltige Sanitär-systeme für Mali – Mission/Vorstudiezur Erarbeitung eines nachhaltigenSanitärkonzepts am Beispiel derStädte Koulikoro und Kati, BerichtPhase A. CD-ROM, April 2000 (Fa.OtterWasser GmbH on behalf of theGTZ)

Black M.: Mega-Slums. The ComingCrisis. WaterAid, 1994

Brikké F.: Management of Operationand Maintenance in Rural DrinkingWater Supply and Sanitation. WHO,Geneva, August 1993

Cairncross S., Feachem R. G.:Environmental Health Engineering inthe Tropics. John Wiley and Sons 1983

Chleq J.-L., Dupriez H.: VanishingLand and Water. Macmillan Publishers,Hong Kong, 1988

Coad A.: Lessons from India in SolidWaste Management. WEDC UK

Cointreau-Levine S.: Urban Manage-ment Programme – Participation inMunicipal Solid Waste Services inDeveloping Countries, Volume 1UNDP/UNCHS/World Bank 1994

Cotton A., Franceys R., Pickford J.,Saywell D.: On-Plot Sanitation inLow-Income Urban Countries. WEDC,UK, September 1995

Cotton A., Saywell D.: On-PlotSanitation in Low-Income UrbanCommunities – Guidelines forSelection. WEDC, 1998

Feachem R.G., Bradley D.J.,Garelick H.; Mara D.D.: Sanitationand Disease Health Aspects of Excretaand Wastewater Management. JohnWiley & Sons 1983

GFA-Umwelt: Utilisation of OrganicWaste in (Peri-) Urban Centres – Supraregional Sectoral Project.Bonn/Eschborn, 1999 (on behalf ofthe GTZ)

Hasse R.: Rainwater Reservoirs aboveGround Structures of Roof CatchmentBotswana 1987

Hogrewe W., Joyce S.D., Perez E. A.:The Unique Challenges of ImprovingPeri-Urban Sanitation. WASHTechnical Report No.86, July 1993

Holmes John R.: Managing SolidWastes in Developing Countries. J.Wiley and Sons, 1984

Kalbermatten J.M., Julius DeAnneS., Mara D, Gunnerson C. G.:Appropriate Technology for WaterSupply and Sanitation – A Planner'sGuide. Transportation, Water andTelecommunication Department; TheWorld Bank, December 1980

Kalbermatten J.M., Julius DeAnneS., Gunnerson C.G.: AppropriateSanitation Alternatives – A Technicaland Economical Appraisal. The JohnsHopkins University Press Baltimoreand London1982

Kerr C.: Community Health andSanitation. Intermediate TechnologyPublications, UK 1990

Mara M., Cairncross S.: Guidelinesfor the Safe Use of Wastewater andExcreta in Agriculture. WHO, Geneva,1989

LITERATURE QUOTED IN THETEXT

OTHER LITERATURE

136

ANNEX

LITERATURE

Muguti E., Everts S., Schulte B.,Smallegange L.: Energy Efficiency forMedium and Small Enterprises; Intermediate Technology Publications,London, 1999

Nill, D., et al: Soil Erosion by Water inAfrica. GTZ, TZ-Verlag Roßdorf, 1996

N.N.: Abfallwirtschaft mit Bevölke-rungsbeteiligung, Ein Beispiel ausNepal. GTZ, Eschborn 1988

N.N.: Conversion of Wastewater intoSafe, Clean Water using Low-CostNatural Methods. Biogas Forum No.62, 1995

N.N.: Drainage. GTZ, Eschborn 1992

N.N.: Environmental and HealthAspects of Planning Urban AreasWHO, Geneva 1993

N.N.: Fact Sheets on EnvironmentalSanitation. WHO, Geneva 1996

N.N.: Technical Brief No.52: Water.Quality or Quantity? Waterlines Vol.15No.4 April 1997

N.N.: Urban EnvironmentalManagement Guidelines Thailand;Solid Waste Management. GTZ,Eschborn 1994

N.N.: Urban EnvironmentalManagement Guidelines Thailand;Environmental Health. GTZ, Eschborn1994

N.N.:Technical Brief No. 54: EmptyingLatrine Pits. Waterlines, Vol. 16, No. 2,Oct. 1997

N.N.: Conversion of Wastewater intoSafe, Clean Water using Low-CostNatural Methods; Biogasforum1995/III No.62, BORDA, Bremen

N.N.: Public Health Engineering inEmergency Situation. Médecins SansFrontières, Paris, 1994

N.N.: La Lutte Anti-Erosive.Republique du Burundi, 1990

N.N.: The Soil – How to Conserve theSoil. FAO, Rom, 1976

N.N.: Erosion Control in the Tropics;Agrodok 11. Agromisa, Wageningen,1987

N.N.: Simple Soil and Water Conser-vation Methods for Upland Farms;Maguugmag Foundation, Inc.; Cebu,Philippines,

N.N.:Utilisation of Organic Waste in(Peri-)Urban Centres. GTZ/GFA-Umwelt, Eschborn 1999

N.N.: Sanitation Promotion Kit, DryToilets in El Salvador; WHO, Geneva 1997

N.N.: Decentralised Disposal ofCommunal Waste Water. BWSS-ISP,GTZ, Eschborn/Bengkulu, 1996

N.N.: Cholera and other EpidemicDiarrhoeal Diseases – Fact Sheets onEnvironmental Sanitation; WHO, Genf,1996

Otis R.J., Mara D.: The Design ofSmall Bore Sewer SystemsUNDP, World Bank, May 1985

Pfammatter R., Schertenleib R.:Non-Governmental Refuse Collectionin Low-Income Urban Areas – LessonsLearned from Selected Schemes inAsia, Africa and Latin America.SANDEC Report No. SwitzerlandMarch 1996

Pickford J., Barker P., Coad A., InceM., Shaw R., Skinner B., Smith M.:Water, Sanitation, Environment andDevelopment. Selected Papers of the19th WEDC Conference Accra, Ghana1993

Proyecto Atención Primaria deSalud – APS (GTZ): Microempresasde Recolección Manual y Transportede Basuras Domésticas. Bogotá

Reed R.A.: Sustainable SewerageWEDC, 1995

Reed, R.A.: Sustainable Sewage.Intermediate Technology Publications,London, 1995

Sasse, L.: DEWATS – DezentraleAbwassserreinigung inEntwicklungsländern; BORDA,Bremen, 1998

Schweizer F., Collins K. A.: ThePrivatisation of Solid WasteManagement in Ghana. Trialog 48,1996

Simpson-Hebert M., Wood S.:Sanitation Promotion Kit. WHO,Geneva 1997

Sobral M., Florencio L., Kato M.T.:Abwassernachbarschaften – einewirksame und billige Alternative fürEntwicklungsländer. Diskussions-forum, TU-International 34/35November 1996

Strauss M., Heinss U., Larmie S. A.:Solids Separation and Pond Systemsfor the Treatment of Faecal Sludges inthe Tropics. EAWAG, SANDEC,Switzerland1998

Vest H., Jantsch F.: Management ofSolid and Liquid Waste at SmallHealthcare Facilities in DevelopingCountriesGTZ, Eschborn 1999

Vest H., Jantsch F.: Umweltkatalog:Abfälle aus medizinischenEinrichtungen. BMZ/GTZ, 1999

Wehenpohl G.: Abfallbeseitigung inMarginalsiedlungen vonEntwicklungsländern. Darmstadt 1987

Wehenpohl G.: Selbsthilfe undPartizipation bei siedlungswasser-wirtschaftlichen Maßnahmen inEntwicklungsländern – Grenzen undMöglichkeiten in städtischen Gebietenunterer Einkommensschichten;Schriftenreihe WAR 30. Darmstadt1987

Winblad U., Kilama W.: Sanitationwithout Water. SIDA, Stockholm 1985

OTHER LITERATURE

137

Fig. 1-4: B.U.S. photo archiveFig. 5-7: Frank SamolFig. 8-9: B.U.S. photo archiveFig. 10-11: Photo archive Dr. Heino VestFig. 12: GTZFig. 13: Photo archive Dr. Heino VestFig. 14: KfW Annual Report 1997Fig. 15: Prof. Peter HerrleFig. 16: Photo archive Dr. Heino VestFig. 17-20: Frank SamolFig. 21: B.U.S. photo archiveFig. 22: Photo archive Dr. Heino VestFig. 23: B.U.S. photo archiveFig. 24-26: Photo archive Dr. Heino VestFig. 27-29: Frank SamolFig. 30-32: Photo archive Dr. Heino VestFig. 33: Frank SamolFig. 34-36: Photo archive Dr. Heino VestFig. 37-38: Frank SamolFig. 39-43: Photo archive Dr. Heino VestFig. 44: Environmental Health Engineering in the Tropics;

John Wiley and Sons, 1983, S.199, 201Fig. 45-48: Photo archive Dr. Heino VestFig. 49: Frank SamolFig. 50-53: Photo archive Dr. Heino VestFig. 54: Business brochure Gross Apparatebau GmbH, HeilbronnFig. 55-64: Photo archive Dr. Heino VestFig. 65: Public Health Engineering in Emergency Situation;

Médecins Sans Frontières, Paris, 1994, S. II-32, II-33Fig. 66-67: Photo archive Dr. Heino VestFig. 68-70: B.U.S. photo archiveFig. 71: Prof. Peter HerrleFig. 72-73: GTZFig. 74: Frank SamolFig. 75 Prof. Peter HerrleFig. 76: Photo archive Dr. Heino VestFig. 77: Photo archive Dr. Heino VestFig. 78: Wastewater Treatment and Excreta Disposal in

Developing Countries; gate/INFU, Eschborn/Dortmund, 1980, S. 6

Fig. 79: Wastewater Treatment and Excreta Disposal in Developing Countries; gate/INFU, Eschborn/Dortmund, 1980, S. 9


ANNEX

ILLUSTRATION CREDITS

LIST OF PHOTOS AND ILLUSTRATIONS

138

ANNEX


Fig. 81: B.U.S. photo archiveFig. 82: Wastewater Treatment and Excreta Disposal in


Fig. 83: Wastewater Treatment and Excreta Disposal in Developing Countries;gate/INFU, Eschborn/Dortmund, 1980, S. 7

Fig. 84: Ecological Sanitation; SIDA, Stockholm 1998, S. 51Fig. 85: Sanitation Promotion Kit, Dry Toilets in El Salvador; WHO,

Geneva 1997, S. 2Fig. 86: Sanitation without Water; The Macmillan Press Ltd.,

Hong Kong 1992, S. 33Fig. 87: EcoSan Center; www.cepp.cc/ecosan/ecosanphotos.htmlFig. 88: Frank SamolFig. 89: Photo archive Dr. Heino VestFig. 90: EcoSan Center; www.cepp.cc/ecosan/ecosanphotos.htmlFig. 91: B.U.S. photo archiveFig. 92-93: Wastewater Treatment and Excreta Disposal in


Fig. 94: Decentralised Disposal of Communal Waste Water; BWSS-ISP, GTZ, Eschborn/Bengkulu, 1996, Annex 2.1

Fig. 95a/b: Energy Efficiency for Medium and Small Enterprises; Intermediate Technology Publications, London, 1999, S. 47

Fig. 96: Wastewater Treatment and Excreta Disposal in Developing Countries;gate/INFU, Eschborn/Dortmund,1980, S. 36

Fig. 97: Wastewater Treatment and Excreta Disposal in Developing Countries;gate/INFU, Eschborn/Dortmund, 1980, S. 38

Fig. 98: GTZ, Klaus WeistrofferFig. 99: DEWATS – Dezentrale Abwassserreinigung in

Entwicklungsländern; BORDA, Bremen, 1998, S. 74Fig. 100: Wastewater Treatment and Excreta Disposal in


Fig. 101: Cholera and other Epidemic Diarrhoeal Diseases; Fact Sheets on Environmental Sanitation; WHO, Genf, 1996

Fig. 102: Sim Van der Ryn; The Toilet Papers Recycling Waste and Conserving Water;Ecological Design Press, 1995

Fig. 103: Emptying Pit Latrines; Technical Brief No. 54; Waterlines Vol. 16, No. 2, October 1997



Fig. 106: Mega-Slums – The Coming Crisis; WaterAid, 1994, S. 22

LIST OF PHOTOS AND ILLUSTRATIONS

139

Fig. 107: John M. Kalbermann, DeAnne S. Julius, D. Duncan Mara, Charles G. Gunnerson;Appropriate Technology for Water Supply and Sanitation;A Planner´s Guide, World Bank, 1980

Fig. 108-110: Photo archive Kraft EngineeringFig. 111-112: PRIMED – Programa Integral de Mejoramiento de Barrios Subnormales en Medellin:

Una Experiencia Exitosa en la Intervención, Medellin 1996Fig. 113: Frank SamolFig. 114: PRIMED – Programa Integral de Mejoramiento de Barrios Subnormales en Medellin:

Una Experiencia Exitosa en la Intervención, Medellin 1996Fig. 115: GTZ sectoral project “Ecological Sanitation” and

GTZ project “Verbesserung des kommunalen Managementsder Wasser- und Abfallwirtschaft Koulikoro, Mali”;Modellhafte nachhaltige Sanitärsysteme für Mali, Mission/Vorstudie zur Erarbeitung eines nachhaltigen Sanitärkonzeptesam Beispiel der Städte Koulikoro und Kati; Bericht Phase A,April 2000

Fig. 116: John M. Kalbermann, DeAnne S. Julius, D. Duncan Mara, Charles G. Gunnerson;Appropriate Technology for Water Supply and Sanitation;A Planner´s Guide, World Bank, 1980

Fig. 117: PRIMED – Programa Integral de Mejoramiento de Barrios Subnormales en Medellin:Una Experiencia Exitosa en la Intervención, Medellin 1996

Fig. 118-119: GTZ sectoral project “Ecological Sanitation” andGTZ project “Verbesserung des kommunalen Managementsder Wasser- und Abfallwirtschaft Koulikoro, Mali”;Modellhafte nachhaltige Sanitärsysteme für Mali, Mission/Vorstudie zur Erarbeitung eines nachhaltigen Sanitärkonzeptesam Beispiel der Städte Koulikoro und Kati; Bericht Phase A,April 2000

Fig. 120 B.U.S. photo archiveFig. 121: La Lutte Anti-Erosive; Republique du Burundi, 1990Fig. 122: PRIMED – Programa Integral de Mejoramiento de Barrios Subnormales en Medellin:

Una Experiencia Exitosa en la Intervención, Medellin 1996Fig. 123: La Lutte Anti-Erosive; Republique du Burundi, 1990Fig. 124: Frank SamolFig. 125: Photo archive Dr. Heino VestFig. 126: PRIMED – Programa Integral de Mejoramiento de Barrios Subnormales en Medellin:

Una Experiencia Exitosa en la Intervención, Medellin 1996Fig. 127: Compilation from:

Management of Operation and Maintenance in Rural Drinking Water Supply and Sanitation, WHO, Geneva August 1993; S. 3Rainwater Reservoirs above Ground Structures of Roof Catchment, Botswana 1987, S. 23

Fig. 128: Rainwater Reservoirs above Ground Structures of Roof Catchment, Botswana 1987, S. 24

Fig. 129: Rainwater Reservoirs above Ground Structures of RoofCatchment, Botswana 1987, S. 74

Fig. 130: Photo archive Dr. Heino Vest

ANNEX


Dag-Hammarskjöld-Weg 1-5Postfach 518065726 EschbornTelefon: ++49 (0)61 96 79-0Telefax: ++49 (0)61 96 79-11 15Internet: http://www.gtz.de

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