AT-SWM-unit(5&6)
description
Transcript of AT-SWM-unit(5&6)
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SOLID WASTE MANAGEMENT
M.Sc Environmental Design
ALLAMA IQBAL OPEN UNIVERSITY ISLAMABAD
January 25, 2014
Muhammad Abid
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Solid Waste Management - History
Waste treatment and disposal has been motivated by concern for
Public Health.
Migration of People started due to Industrial Revolution between
1750 and 1850.
Massive expansion of the population living in towns and cities,created high volume of domestic, commercial and industrial
waste i.e. broken glass, rusty metal, food residue and human
waste, which was dangerous to human health.
Waste attracted flies, rats and other vermin, which in turn posedpotential threats through the transfer of disease. This led to an
increasing awareness of the link between public health and the
environment.
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Solid Waste Management - History
SWM is potential threat to human health, legislation wasintroduced on a local and national basis in many countries.
Waste treatment and disposal has been motivated by
concern for public health.
Introduction of Acts (UK 1875/1936) - Removal andDisposal of Waste and into Water
In USA Acts were introduced in 1795, 1856
Purpose built municipal waste Incinerators were introducedin the UK in the late 1870s and by 1912 there were over 300
waste incinerators in the UK, of which 76 had some form of
power generation
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Solid Waste Management - History
Incineration plants reached the end of their operationallifetime, they tended to become scrapped in favor of
landfill.
Environmental implications of merely dumping the waste
in open sites and later with increase waste began to beburied.
Burying the waste had the health advantages of reducing
odours, and discouraging rats and other vermin. Series of incidents in the late 1960s and 1970s highlighted
waste as a potential major source of environmental
pollution.
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Solid Waste Management - Pakistan
In Pakistan SWM, need increased for using disposableitems i.e. plastic bags etc., which cause drainage
problems.
In Karachi - 50% of the citys daily generation of 7,000
tons of rubbish - Collected by the Municipal service,
while the rest remains at collection points and on Dump
sites
Urban environment in Pakistan continues to deteriorate,there is growing recognition of the need for a Sanitation
policy with sound operational strategies.
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Solid Waste Management - Pakistan
Informal Recycling of Domestic WasteTwoCategories:
Waste picking in streets, communal bins, transfer
points and disposal sites.
Waste separation at the household stage and selling
onto itinerant waste buyers.
Above waste passes through a #of dealers in trading
and recycling, before it reaches the recycling industry.
The SWM system starts from the Households and ends
with the disposal or reuse of the materials
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Solid Waste Management - Pakistan
Informal Sector
There are independent operators dealing in waste collection,
purchase, separation, restoration, and resale and recycling
Kabaris are large-scale waste dealers who operate from
shops and warehouses. There are approximately 1,000 inKarachi and most specialize in just one type of waste, which
they buy at auctions or from middle dealers and resell to
recycling plants, or recycle themselves.
Waste Busters collect rubbish from households and charge
about PKR 200 a month
Few Local NGOsCrush vegetables to produce liquid
concentrate for pesticides, fertilizer and Bin designs
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Solid Waste Management - Pakistan
Recycling Waste Materials
Waste Material Common Reuse and RecyclingBroken glass Glass bottlesBottles Washed and used againBread Livestock feedNewspapers Various types of packingFerrous metal Recycled in re-rolling millsPaper Cardboard etc.Aluminium Re-melt in moulds for various industriesPlastics Uses/recycling depends upon type: toys, shoe soles, shopping bags, sandals
etc.Plastic bags Buckets and other household containersMagazines, books Sold again at reduced prices
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Cleaner Production Opportunity for
the Industrial Sector of Pakistan Industrial Sector in Pakistan accounts for 18% of GDP
Environmental Degradation due to the uncontrolled and
inefficient use of natural resources, low industrial
productivity, excessive generation of hazardous waste and
the uncontrolled release of solid wastes, air pollutants anduntreated wastewater into the natural environment has
become a major problem in Pakistan.
The major Polluting Industries are tanneries, textile,
petroleum, pesticides, fertilizer etc.
Majority of the multinational companies in Pakistan are also
now going for certification due to their corporate policy.
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Cleaner Production Opportunity for
the Industrial Sector of Pakistan Till now 20 to 25 companies have achieved ISO 14000
certification, mostly multinationals, whereas remaining are
exportbased industries.
Most of the Local Companies are still reluctant towards due
to wrong perception that environmental solutions cannot beeconomically viable.
Lack of expertise available locally, there is a critical need
for capacity building program for pollution control,
promotion of environmentally sustainable development and
creation of awareness
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Cleaner Production Opportunities
for Industries Cleaner Production Opportunities for Industries
Cleaner production (CP) is a strategy for enhancing productivity and
environmental performance for socio-economic development.
Application of Appropriate Techniques, Technologies and
Management Systems to produce environmentally compatible goodsand services.
Improvements in productivity and environmental performance
achieved through CP bring bottom line savings, profit/efficiency.
In-house improvements and CP technologies will not only result inthe improvement of economic and environmental performance of the
unit, but will also reduce the cost of end-of-pipe treatment.
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Cleaner Production Opportunities
for Industries Cleaner Production Opportunities for Industries
Cleaner Production technologies already used in the country
Scrubbers
Dust Filters
Economizer
Vacuum Cleaners
High Pressure Cleaning Devices
Condenser
Grease Trap
Incinerators
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Cleaner Production Opportunities
for Industries Waste
The definition of waste can be very subjective; what represents waste to one person
may represent a valuable resource to another
Definition of 'Waste' Production or consumption residues not otherwise specified below.
Off-specification products.
Products whose date for appropriate use has expired. Materials spilled, lost or having undergone other mishap, including any materials, equipment etc. contaminated as a
result of the mishap.
Materials contaminated or soiled as a result of planned actions (e.g. residues from cleaning operations, packing
materials, containers etc.).
Unusable parts (e.g. reject batteries, exhausted catalysts etc.).
Substances which no longer perform satisfactorily (e.g. contaminated acids, contaminated solvents, exhausted tempering
salts etc.).
Residues of industrial processes (e.g. slags, still bottoms etc.).
Residues from pollution abatement processes (e.g. scrubber sludges, baghouse dusts, spent filters etc.).
Machining or finishing residues (e.g. lathe turnings, mill scales etc.).
Residues from raw materials extraction and processing (e.g. mining residues, oil field slops etc.).
Adulterated materials (e.g. oils contaminated with PCBs etc.).
Any materials, substances or products whose use has been banned by law. Products for which the holder has no further use (e.g. agricultural, household, office, commercial and shop discards etc.).
Cl P d i O i i
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Cleaner Production Opportunities
for Industries Types of Waste
Controlled Waste
Household Waste
Industrial Waste
Commercial Waste Clinical Waste
Special Waste
Un-Controlled Waste
Inert Waste
Hazardous Waste
Municipal Solid Waste
Cl P d ti O t iti
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Cleaner Production Opportunities
for Industries Waste Classification Systems
Origin, e.g., clinical wastes, household or urban solid wastes, industrial wastes,
nuclear wastes, agriculture;
Form, e.g., liquid, solid, gaseous, slurries,
powders;
Properties, e.g., toxic, reactive, acidic,alkaline, inert, volatile, carcinogenic;
Legal definition, e.g., special, controlled,
household, industrial, commercial.
Properties of Waste
Series of descriptors for different types of
wastes:
Code DescriptionHI ExplosiveH2 OxidizingH3A Highly flammable
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Cleaner Production Opportunities
for Industries Subdivisions of General HHs, Commercial and Industrial Waste Category:
General household, commercial and industrial waste
Separate components of general waste
Vegetable matter
Animal matter
Animal or vegetable oil, fat, wax, grease Sewage
Subdivisions of the Organic Chemical Wastes Category:
Paints, resins and adhesives
Inks and dyestuffs
Cosmetics, Surfactants and Chelating Agents
Monomers and Precursors, Tarry wastes
Pharmaceuticals , Pesticides
Organic Chemical Process Wastes, Additional Codes
Cl P d ti O t iti
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Cleaner Production Opportunities
for Industries Typical Composition and Properties of Sewage Sludge
PropertyTypical value
Calorific value 21.3
MJ/kg (dry, ash free)Ash content
37%Composition of combustible fraction (dry, ash free)Carbon
53.0%Hydrogen
7.7%Oxygen
33.5%Nitrogen
5.0%Sulphur
0.8%Organic composition (dry, ash free)Crude protein
30.0
Crude fat
13.0Crude fiber
33.0Non-fibrous carbohydrate 24.0
Cl P d ti O t iti
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Cleaner Production Opportunities
for Industries Physical form of the Waste
Physical form of the waste i.e solid, liquid or sludge etc:
F1 Solid - composite of materials
F2 Solid - mixed materials
F3 Solid - bulky
F4 Liquid - containerized F5 Liquid - bulk
F6 Sludge/slurry - in a solid container
F7 Sludge/slurry - bulk
For Textiles
F8 Clean textiles F9 Dry textiles
For Metals
FI0 Metal rod F11 Metal swarf F12 Metal wire
For Plastic
F 13 Plastic bottles F14 Plastic film F15 Plastic - rigid
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Cleaner Production Opportunities
Waste Containers and Collection System
Type of container used to store the waste generated from households, commercial and
industrial premises depends on i.e. frequency, efficiency of collection, amount of waste,
type of housing, density of collected wastes, collection vehicle type, vehicle usage and
manpower and economics relating to container and the collection system.
The correct size of waste container is important, since it has been shown that the use of
non-standard containers is the greatest cause of litter. Household waste containersinclude traditional metal or plastic dustbins, wheeled bins and plastic sacks. The capacity
of the household waste storage container depends on how many collections are made per
week.
With a general increase in the amount of waste generated, there has been a response to
use bigger or more containers, which also has the potential to reduce manning costs byless frequent waste collections.
Another factor dictating size of container and frequency of collection is climate; in
cooler areas such as Northern Europe, where odour from the degradation of the waste
occurs more slowly, the frequency of collection may be once or twice per week.
Consequently the container must be able to store a full week's volume of waste.
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Cleaner Production Opportunities
Waste is dumped un-segregated and collected by three methods:
Hauled Container System,
Stationary Container System and Bull Carts,
The containers are mostly transported from one place to another with help of a truck or
tractor, which is overflowing and not covered properly. The waste spills out of the
container and a lot of it falls in the streets before reaching the landfill site. Similarly, in
certain areas bull and donkey carts are used to collect the MSW. The cart goes from
street to street picking up the waste and is again not a proper system for waste collection.
A fact sheet on Municipal Solid Waste Management (MSWM) has been developed by
WWF-P with a viewpoint to facilitate the readers on efficient practices of SWM.
The government has initiated a plan to privatize the MSWM in the country. This could
be done using the present network of recyclers and scavengers to collect and processgarbage. It would be in their interest to make arrangements with individual households
and industries to segregate different recyclable at the source. This interest of the private
collector in segregated garbage could be translated in payment in terms of free garbage
collection or cash payment for the segregated material.
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Cleaner Production Opportunities
Land-Fills
Landfilling is the technical term used to Fill large holes in the ground with waste.
This process is also known as land-raising. Landfill sites produce landfill gas (55%
methane and 45% carbon dioxide) which can be partly captured for energy production.
Impacts
Friends of the Earth opposes landfill for the 80% of municipal solid waste that can berecycled or composted for the following reasons:
It wastes valuable resources.
It exacerbates climate change because when materials are buried, more fossil fuel energy
is used to replace the products through mining, manufacturing, and transportation around
the world. It produces methane, a potent greenhouse gas that contributes to climate change.
It creates water pollution through leaching.
It can lead to the contamination of land.
It gives rise to various nuisances including increased traffic, noise, odours, smoke, dust,
litter and pests.
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Cleaner Production Opportunities
Major Advantageswith Landfillingof wastes are the low costs of landfill
compared to other disposal options and the fact that a wide variety of wastes aresuitable for landfill. It should also be remembered that ultimately, many other waste
treatment and disposal options require that the final disposal route for the residues
requires landfill.
Disadvantages with Landfill. Older sites, which in some cases are still in use or
have long been disused, were constructed before the environmental impacts ofleachate and landfill gas were realized.
Landfill gas, in particular, can be hazardous, since the largest component, methane,
can reach explosive concentrations.
All Landfill sites are required to be monitored for landfill gas, and the gas from
operational sites must be controlled via proper venting. Landfill methane gas is alsoa 'greenhouse gas', leading to the problems of global warming but with about 30
times the effect of carbon dioxide.
Selection of a site for a waste landfill depends on a wide range of criteria, including
the proximity of the site to the source of waste generation, suitability of access
roads, the impact on the local environment of site operations, and the geological andh dro eolo ical stabilit of the site.
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Cleaner Production Opportunities
Main aim of the landfill site assessment investigation is the identification of the
possible pathways and receptors of landfill gas and leachate in the surroundingenvironment and the environmental impact of site operations Site assessment
involves appraisal of geological and hydrogeological conditions at the site.
This may include the use of existing surveys, aerial photography, boreholes,
geophysical investigations, geological mapping and sampling etc. The information
allows an assessment of soil and bedrock grain sizes, mineralogy and permeabilitys,and ground water levels.
Inaddition, the previous use of the site, meteorological data, transport infra-structure
and planning use designations, and the planning strategy of the area would also be
assessed.
For large landfill sites an environmental assessment is also required to determine theimpact on the environment. Environmental assessment involves a description and
assessment of the direct and indirect effects of the project on human beings, fauna,
flora, soil, water, air, climate and landscape, material assets and the cultural heritage
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Cleaner Production Opportunities
Considerations for Landfills
A waste landfill is a major design and engineering project and there are a number ofpoints to be considered as part of the process.
Final Landform Profi le
Site capacity
Settlement
Waste density
Mater ials requirements
Drainage
Operational Practice
The typical modern landfill site consists of a secure, fenced, landscaped site with
access routes for waste transport vehicles. The sequence of operations for an
incoming waste vehicle may include the weighing of the lorry on a weighbridge
document inspection and waste inspection. Once cleaned, the lorry would move to
the waste disposal area where the waste is tipped, the wheels of the lorry are cleaned
and the lorry is weighed out if the site to determine the weight of waste deposited.
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Cleaner Production Opportunities
Types of Waste Land Filled
Inert wastes
Bio-reactive wastes
Hazardous/industrial or special waste
Factors Influencing Waste Degradation in Landfills
Site characteristics
Waste characteristic
Moisture content of the waste
Temperature
Acidity
Major Stages of Waste Degradation
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Major Stages of Waste Degradation
in Landfills
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Landfill Design Types
Attenuate and disperse landf i l ls
Containment landfi l ls
Schematic diagram of water balance for an attenuate and disperse landfill site.
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Landfill Gas
Gases arising from Bio-degradation landfills consist of hydrogen and carbon dioxide
in the early stages, followed mainly by methane and carbon dioxide in the laterstages. What is known as 'landfill gas' is a product mainly of the methanogen stage
of degradation of biodegradable wastes.
Landfill gas is produced from household and commercial wastes, which contain a
significant proportion of biodegradable materials however, certain industrial and
commercial wastes, which have been estimated to contain 62% and 66%biodegradable components.
The major constituents of landfill gas, methane and carbon dioxide are odorless, and
it is the minor components such as hydrogen sulphide, organic esters and the
organosulphur compounds, which give landfill gas a malodorous smell. Landfill gas
contains components, which are flammable, and when mixed with air can reachexplosive concentrations in confined spaces.
Some of the trace components of landfill gas have a toxic effect and may be
hazardous if high enough concentrations are reached; for example, hydrogen
sulphide Aromatic hydrocarbons are in low concentration but may potentially have
an adverse effect on the workforce of the landfill site.
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Landfill Gas
The major components of landfill gas, methane and carbon
dioxide, are 'greenhouse gases'. The greenhouse effect is
produced by certain gases in the atmosphere, which allow
transmission of short wave radiation from the sun but are
opaque to long wave radiation reflected from the earth'ssurface, thereby causing warming of the earth's atmosphere.
A molecule of methane has approximately 30 times the
greenhouse effect of a molecule of carbon dioxide.
The quantities of gas produced from waste depend on the
biodegradable fraction of the waste, the presence of
microorganisms, and suitable aerobic and anaerobic
conditions
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Landfill Gas Migration
Gases generated in the landfill will move throughout the mass of waste in
addition to movement or migration out of the site. The mechanism of gasmovement is via gaseous diffusion and advection or pressure gradient.
That is, the gas moves from high to low gas concentration regions or
from high to low gas pressure regions.
Movement of gas within the mass of waste is governed by thepermeability of the waste, overlying daily or intermittent cover, and the
degree of compaction of the waste. Lateral movement of the gases is
caused by overlying low permeability layers such as the daily cover and
surface and sub-surface accumulations of water.
Vertical movement of gas may occur through natural settlement of the
waste, between bales of waste if a baling system is used to compact and
bale the waste, or through layers of low permeability inert wastes such as
construction waste rubble. Where landfill gas extraction is practiced to
recover the gas for energy use, the gas is collected in gas wells, and
Possible Landfill Gas Migration
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Possible Landfill Gas Migration
Pathways for a Closed Site
Management and Monitoring of
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Management and Monitoring of
Landfill Gas
With the recognition of formation of landfill gas and its associatedhazards, and the potential to utilize the energy content of the gas,
the modern landfill site is designed to trap the gases for flaring or
use in energy recovery systems.
However, the priority is for control of the gases to protect theenvironment and prevent unacceptable risk to human health rather
than utilization, and therefore where energy recovery is practiced,
there would also be a control system alongside.
Three types of system used to control landfill gas migration: Passive venting;
Physical barriers;
Pumping extraction systems.
Management and Monitoring of
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Management and Monitoring of
Landfill Gas
Passive Venting Systemsare only recommended for oldsites in the late stages of gas generation where gas
generation rates are low, or where inert wastes are landfilled
and similarly low, or where negligible rates of gas
generation are found.
The passive venting pit consists of a highly permeable vent
of gravel material encased in a geotextile fabric to prevent
ingress of fine material and reduction of permeability. Construction of the passive venting system may be as
emplacement of the waste proceeds or afterwards by drilling
or excavation into the mass of waste. Typically the vents are
placed at intervals of between 20 and 50 m.
Management and Monitoring of
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Management and Monitoring of
Landfill Gas
Physical barr iersuse low-permeability barriers of, for example, flexible polymericgeomembranes, bentonite cement or clay, to contain and restrict the gas migration.
Whilst these barriers might form part of a leachate containment system, they are less
effective in containing gas. Coefficients of permeability for gas containment are required
to be lower than 10-9 m/s. Efficiencies of barriers are improved if they are combined
with a means of removing the gas by either passive venting or pumped extraction.
Pumping extraction systemspump the gas out of the landfill. The gas migrates to gas
pits or wells within the waste, which consists of highly permeable gravel, stones or
rubble with a central perforated plastic pipe. The gases pass through the high-
permeability vent to a plain unperforated pipe, which draws the gases through to the
pump. Leachate vapour may also be pumped out with the gas, and because this vapour
has a high moisture content a leachate condensation trap is required. Figure shows atypical pumping extraction well. The gas pumped to the surface is either flared by self-
sustaining combustion or the use of a support fuel, utilized in an energy recovery system,
or if the gas concentrations are sufficiently low it is discharged to the atmosphere. Where
flaring is used to dispose of the gas minimum flame temperatures between 850 and 1100
C are recommended to destroy any hazardous trace components.
Typical combined Leachate and
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Typical combined Leachate and
Landfill Gas Collection Well
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Landfill Leachate Leachate represents the water, which passes through the waste, and water
generated within the landfill site, resulting in a liquid containing suspendedsolids, soluble components of the waste and products from the degradation
of the waste by various microorganisms. The composition of the leachate
will depend on the heterogeneity and composition of the waste and whether
there is any industrial/hazardous waste co-disposal, the stage of
biodegradation reached by the waste, moisture content and operationalprocedures.
The decomposition rate of the waste also depends on aspects such as pH,
temperature, aerobic or anaerobic conditions, and the associated types of
microorganisms. Associated with leachate is a malodorous smell, due mainly
to the presence of organic acids.
The characteristics of the leachate are influenced by the waste material
deposited in the site. For example, inert wastes will produce a leachate with
low concentrations of components, whereas a hazardous waste leachate
tends to have a wide range of components with highly variableconcentrations.
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Landfill Capping Final cover or capping of the landfill site is required after the final waste has been
deposited. The purpose of the cap is to contain and protect the waste, prevent
rainwater and surface water from percolating into the site and influencing the
generation of leachate, control the release of landfill gas, and prevent ingress of air
and disruption of the anaerobic biodegradation process. In addition, the final cover is
landscaped and provides a soil for the establishment of the restored site plant
materials. The design of the cover system of lining materials used to cap the site
depends on the nature of the waste, for example, whether they are inert orbiodegradable.
Overlying the main body of waste may be the gas collection layer, depending on the
nature of the waste. The gas collection layer is a porous material such as geotextile,
geonet or coarse sand through which the gas can easily permeate to the gas
collection and control system.
A barrier layer is a low permeability layer such as a plastic polymer geomembrane, a
geosynthetic clay liner of bentonite/geotextile fabric, or compacted natural clay. The
barrier layer serves a two-fold purpose: to prevent ingress of water and the egress of
landfill gas. The barrier layer may have a protective geotextile layer above and
below.
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Components of Landfill Capping System
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Landfill Site Completion and Restoration
At the end of the life of a landfill, the landfill operator must
demonstrate that the site has physically, chemically and biologicallystabilized and no longer poses a risk to the public or the local
environment. When a site is deemed complete, post-closure pollution
controls and leachate and landfill gas control systems would no longer
be required. Stabilisation is defined in terms of the quantity andcomposition of the leachate and landfill gas produced at the site.
Assessment of completion depends on the type of landfill site. For
example, sites, which have taken only inert wastes, pose a low risk to
human health and the environment since, only low or zero levels of
leachate and landfill gas are likely to be generated. For biodegradable
wastes such as municipal solid waste, then a full assessment of the
leachate composition and gas volume and the potential future
generation rates, together with an assessment of the waste settlement,
would be required
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Energy Recovery
The development of larger and larger landfill sites throughout many countries has
provided for economies of scale and the economic viability of utilization of landfillgas. The modem site is seen in this context as a 'bio-reactor', used to stabilize waste
and produce landfill gas for energy recovery. Therefore, whilst landfill sites exist
which are used for disposal without energy recovery, the modem purpose-built site
would normally incorporate a landfill gas extraction system for the recovery of
energy.
Estimates of the amount of landfill gas generated throughout the lifetime of a
landfill site are highly variable, with estimates of between 39 and 500 m3/tonne.
Annual rates of gas production have been estimated for a typical municipal solid
waste landfill at between 6 and 8 m3/tonne/year, but much higher rates of over 20
m3/tonne/year have been recorded.
The energy recovery technology is based around the gas collection system and the
pre-treatment and power generation technology. Gas collection is via either vertical
gas wells or horizontal well collection systems, depending on the type of site, site-
filling techniques, depth of waste and leachate level. The gas is collected in a series
of perforated gas pipelines connected to a central pipeline.
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Waste Treatment Technologies
Recycling
Recycling is the collection and separation of materials from waste and subsequentprocessing to produce marketable products.
Benefits
Recycling basic materials in order to make new products has several benefits:
It reduces the demand for raw materials by extending their life and maximising the
value extracted from them.
It reduces the habitat damage, pollution and waste associated with the extraction of
raw materials.
It reduces transport costs and pollution from transporting raw materials and
manufacturing new products.
It saves energy in the production process when compared with the energy consumed
in using raw materials.
It reduces emissions to air and water in the production process.
It reduces disposal impact (if more waste is recycled, less waste goes to landfill or
incinerators).
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Waste Treatment Technologies
Composting
The process of composting is one of biological decomposition under aerobic (openair) and thermophilic (at or above 70C) conditions, which breaks down organic
material to leave a humus rich residue, the compost. Compost is a valuable soil
conditioner for both agriculture, gardening and forestry.
Benefits
Composting is an excellent method of managing solid waste with a high organiccontent (i.e. biodegradable waste) such as garden waste, kitchen waste, park waste,
and even scrap paper and cardboard. 60% of municipal solid waste can be
composted.
Composting techniques
Home composting Compost can be made at home using a traditional compost heap,
a purpose designed container or a wormery.
Community composting
Open/Open air windrow
Enclosed/Covered windrow
In-vessel
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Waste Treatment Technologies
Incineration Ration
Incineration is the combustion of waste at high temperatures. It uses a wide variety ofcombustion systems developed from boiler plant technology and also more novel techniques
such as molten salt and fluidized bed incinerators.
Incineration of waste has a number of advantages over landfill
Incineration can usually be carried out near the point of collection. The number of landfill
sites close to the point. of waste generation are becoming scarcer, resulting in transport of
waste over long distances.
The waste is reduced into a biologically sterile ash product, which for municipal solid waste
is approximately one-tenth of its pre-burnt volume and one-third of its pre-burnt weight.
Incineration produces no methane, unlike landfill. Methane is a 'greenhouse gas' and is a
significant contributor to global warming.
Waste incineration can be used as a low cost source of energy to produce steam for electricpower generation, industrial process heating, or hot water for district heating, thereby
conserving valuable primary fuel resources.
The bottom ash residues can be used for materials recovery or as secondary aggregates in
construction.
Incineration is the best practicable environmental option for many hazardous wastes such ashighly flammable, volatile, toxic and infectious waste.
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Incineration - Disadvantages
It generally entails much higher costs and longer pay back periods due to the high capital investment
The incinerator is designed on the basis of a certain calorific value for the waste. Removal of materials such as
paper and plastics for recycling may reduce the overall calorific value of the waste and consequently may affectincinerator performance.
The incineration process still produces a solid waste residue which requires management.
It destroys valuable resources.
It exacerbates climate change because when materials are burned, more fossil fuel energy is used to replace the
products through mining, manufacturing, and transportation around the world. Energy from burning waste is not
renewable. It undermines councils recycling schemes by demanding long-term waste delivery - Because it takes 15-25
years for a waste management company to make a return on their capital investment, the contract between a
council and a waste management company requires the council to provide an agreed amount of waste for at least
25 years.
It produces emissions of nitrogen oxides, particulates, heavy metals and dioxins, all of which are potentially
dangerous to human health.
It produces bottom ash, which may contain heavy metals and dioxins present in the waste burnt, such as
batteries. Bottom ash represents one-third by weight of the original waste and still has to be land filled.
It also produces fly ash (the fine particles and gases caught in the chimney by filter systems), which is
undisputedly toxic, containing pollutants such as heavy metals and dioxins. Fly ash is classified as special waste
(i.e. hazardous waste) and has to be landfilled in very careful circumstances.
It creates very few jobs. The recycling industry however offers enormous potential for substantial job creation.
It is a much more capital-intensive and costly approach than recycling. It creates more noise and traffic. Incinerators can also be re arded as e esores.
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Incineration - Disadvantages
The modern incinerator is an efficient combustion system with
sophisticated gas clean-up which produces energy and reduces the wasteto an inert residue with minimum pollution. Incineration plants may be
classified on a variety of criteria, for example, their capacity, the nature
of the waste to be combusted, the type of system etc. However, a broad
division can be made between mass burn incineration and other types.
Mass burn incineration:Large scale incineration of municipal solid
waste in single-stage chamber unit in which complete combustion or
oxidation occur Typical throughputs of waste are between 10 and 50
tonnes per hour.
Other types of incineration:Other types of incineration involve smallerscale throughputs of between 1 and 2 tonnes per hour of wastes such as
clinical waste sewage sludge and hazardous waste. Typical examples of
such systems include fluidized bed, cyclonic, starved air or pyrolytic,
rotary kiln, rocking kiln, cement kiln, and liquid and gaseous
incinerators.
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Incineration - Disadvantages
Incineration in Pakistan
June 12 was the first World Incineration Day that was observed in Pakistan - whose record onenvironment, solid waste management, health and hygiene of its citizens, is dismal and
pathetic, with the added dilemma that, since its coffers are depleted, whether to invest in such
a contentious technology!
Currently, the majority of hospitals in Pakistan are dumping their waste, which includes both
hazardous and non-hazardous waste, in open grounds just like the municipal waste. This
allows the scavengers to take advantage of anything they may deem valuable, such assyringes, blood bags, catheters, scalpels etc, which they may sell or recycle/ re-use to
deleterious effect. To compound our problem, Pakistan does not have a single sanitary
engineer and in general has been unable to dispose of even the municipal waste with any
worthwhile success. In the light of such an alarming situation, the practice of dumping
hospital waste in open fields is extremely dangerous and hazardous for the health and life of
human beings and nature. Currently, the landfills in Pakistan are just open dumpsites whereanimals graze or scavenge for food and the poor earn their livelihood.
There are 24 incinerators in Pakistan. Only six are operating and that too not according to the
international standards. Resultantly, the process of incineration is not being carried out
properly and the waste is not being detoxified. At the same time, poisonous fumes, like
dioxins, are being emitted into the atmosphere through the chimneys of these incinerators,
which only adds to the plight of people of Pakistan.
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Incineration - Disadvantages
Incinerators, when operating properly burn at extremely high temperatures - in access of
1100 degrees Celsius, thereby only emitting carbon dioxide and water vapor into the
atmosphere. Conversely, the incinerators in Pakistan also emit a lot of smokea direct
indicator of low temperature burning and pose a direct threat to human life. Therefore, it
is essential to address the technology of incineration and the management aspect of it in
Pakistan. Whereas, the very same technology has been a success and is widely used in
the developed countries, where landfills are now discouraged due to the scarcity of
barren lands. Pakistan's case is not all that different. We have an agro-based economyand our land is extremely precious to waste it on dumpsites, which would ultimately
contaminate our other scarce commodity - water!!
The chimneys of incinerators should only emit carbon dioxide and water, and planting
more trees - nature's filtering agents - may solve this rise in 'green house' gases
Furthermore, the heat generated from incinerators may be used to produce steam, whichin turn could be used to drive turbines and generate electricity and at least supply a small
community with the much-needed resource to enhance development. In a country like
Pakistan where such resources are scarce, large-scale industrial incinerators could help
address the use of renewable energy and help in solving the crisis besieged in the rural
areas. Such endeavors have been successfully implemented throughout the developed
world.
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Anaerobic Digestion
Anaerobic digestion is a biological process in which organic
material is broken down by the action of microorganisms.Unlike composting, the process takes place in the absence of
air. The residue remaining after digestion can be used as a
soil conditioner and the process generates a gas, which can
be used as a fuel for domestic or industrial use. The
anaerobic digestion process is very similar to anaerobic
breakdown of organic waste in landfill sites but under
controlled conditions. Friends of the Earth supportsanaerobic digestion for sorted organic waste.
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Gasification
Gasification is where carbon based wastes are heated in the
presence of air or steam to produce fuel-rich gases. Thetechnology is based on the reforming process to produce
town gas from coal, and requires industrial scale facilities.
From the end of 1998, the dumping of sewage sludge at sea
has been prohibited. Friends of the Earth opposes
gasification for the 80% of municipal solid waste that can
be recycled or composted because it wastes valuable
resources, contributes to climate change and provides veryfew jobs.
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Pyrolysis
In this treatment, carbon based wastes are heated in the
absence of air to produce a mixture of gaseous and liquidfuels and a solid inert residue (mainly carbon). Pyrolysis
generally requires a consistent waste stream such as tyres or
plastics to produce a usable fuel product. Currently, there is
only one facility established in the UKtaking in tyres .
This has been shut because of operational problems. Friends
of the Earth opposes pyrolysis for the 80% of municipal
solid waste that can be recycled or composted for the samereasons that it opposes gasification.
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