Water Filtration For Developing Nations

Derek Humenny Dimitra Panagiotoglou

A thesis submitted in partial fulfilment of the requirements for the degree of

BACHELOR OF APPLIED SCIENCE

Supervisors: Professors W.L. Cleghorn and J.K. Mills Industrial Partner: Richie Singh, Creative Engineering Services Inc.

Abstract

Clean, safe drinking water remains unavailable to a large portion of the global population. This most basic of human rights, and requirement for healthy living should not be a commodity exclusive to the economic elite. While several technologically sophisticated solutions improve water quality in affluent regions equipped with adequate infrastructure, these solutions are not appropriate for more rural, rudimentary, low-cost demands.

This paper discusses eight common filtration technologies, analyzing them in context of their application in the developing world. The best solution must be compatible with the economical, technological and educational limitations of the large, target populace, while still achieving appropriate sanitation standards (as set out by the World Health Organization, WHO) and water consumption demands. To that end, Slow Sand Filtration has been selected as appropriately meeting these goals. The Slow Sand filter used for the Life Cycle Analysis is estimated to cost $5.59 (2008 USD) to produce and run, require minimal infrastructure to produce and run, while meeting WHO standards and has an estimated lifespan of 100 years. Experimentation was used to verify the capabilities of slow sand filtration. The test model produced a 75% reduction in coliform bacteria while maintaining flow rates of up to 1926L/day.

i

Acknowledgements

Thanks to Damien Boyd, Kelly Hodgson, Aaron Hong, Andrew and Wendy Humenny, Dr.

David James, and Brian Mitchell for their contributions to the success of this thesis.

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Method of Attribution

The work was divided evenly and reflective of each student’s particular strengths. The

background research on filtration methods, and model construction were conducted by both

students. Data analysis and explanation, as well as editing were done by Dimitra Panagiotoglou,

with prototype design and monitoring, report compilation and formatting by Derek Humenny.

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Table of Contents

Acknowledgements........................................................................................................................... i

Method of Attribution ..................................................................................................................... ii

List of Symbols Used ........................................................................................................................ v

List of Figures .................................................................................................................................. vi

List of Tables .................................................................................................................................. vii

Chapter 1 – Introduction.................................................................................................................. 1

Motivation ................................................................................................................................... 1

Objectives .................................................................................................................................... 2

Chapter 2 – Water Consumption and Demand ............................................................................... 4

Target Demographic .................................................................................................................... 4

Target Contaminants ................................................................................................................... 6

Data Analysis ................................................................................................................................ 6

Division of GEMStat Data ............................................................................................................. 8

Data Trends .................................................................................................................................. 9

Water Source ............................................................................................................................... 9

Chapter 3 – Water Filtering Methods ............................................................................................ 11

Granular Media Filtering ............................................................................................................ 11

Sand........................................................................................................................................ 12

Anthracite .............................................................................................................................. 14

Barrier Media Filtering ............................................................................................................... 15

Membrane Technology .......................................................................................................... 15

Ceramic .................................................................................................................................. 20

Concrete ................................................................................................................................. 21

Disinfection Treatment .............................................................................................................. 22

Ultraviolet Radiation .............................................................................................................. 22

Chemical Purification ............................................................................................................. 24

Carbon Adsorption ..................................................................................................................... 26

Chapter 4 – Technology Assessment ............................................................................................. 29

Method Selection ....................................................................................................................... 29

Slow Sand Filtration Improvements ........................................................................................... 30

Life Cycle Analysis ...................................................................................................................... 34

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Premanufacture ..................................................................................................................... 35

Manufacture .......................................................................................................................... 36

Distribution/Transportation................................................................................................... 36

Use ......................................................................................................................................... 37

Maintenance .......................................................................................................................... 37

End of Life .............................................................................................................................. 39

Chapter 5 – Prototype .................................................................................................................... 40

Functional Requirements ........................................................................................................... 40

Design......................................................................................................................................... 41

Basic Operation ...................................................................................................................... 41

Function ................................................................................................................................. 42

Materials ................................................................................................................................ 43

Methods ..................................................................................................................................... 43

Contaminated Water Source ................................................................................................. 43

Testing Procedure .................................................................................................................. 44

Test Sample Analysis .............................................................................................................. 45

Chapter 6 – Sample Analysis .......................................................................................................... 46

Test Results ................................................................................................................................ 46

Discussion .................................................................................................................................. 46

Sources of Error ......................................................................................................................... 49

Chapter 7 – Recommended Future Actions ................................................................................... 51

Chapter 8 – Conclusion .................................................................................................................. 52

Chapter 9 – Tables and Figures ...................................................................................................... 54

Glossary .......................................................................................................................................... 64

Works Cited .................................................................................................................................... 65

Appendix A – GEMStat Analysis ..................................................................................................... 72

Appendix B – Darcy’s Law Derivation and Application .................................................................. 74

Appendix C – EIOLCA of Filter Parts ............................................................................................... 75

Appendix D – Contribution to Final Document .............................................................................. 76

Appendix E – Detailed Prototype Drawings ................................................................................... 78

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List of Symbols Used

Chapter 1

Atlas Conversion Factor (national currency to the USD) for year t

Average annual exchange rate (national currency to the USD) for year t

GDP deflator for the year t

SDR deflator in USD terms for year t

Atlas GNI per capita in USD in year t

Current GNI (local currency) for year t

Midyear population for year t

National Population

Average Domestic Water Footprint of the Population

Calculated weighted domestic average per capita

Appendix B

Q Volumetric flow rate

κ Permeability

A Cross-sectional area

μ Dynamic viscosity

L Filter bed depth

K Hydraulic conductivity

γ Specific weight of fluid

ρ Density of fluid

g gravity = 9.814

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List of Figures

Fig 2.1 – Iron Contamination in Asia

Fig 2.2 – Sulphate Contamination in Africa

Fig 2.3 – Population Representation for Africa

Fig 3.1 – Membrane Cross-Flow Filtration

Fig 3.2 – Effective Removal of Pathogens for Membrane Technologies

Fig 5.1 – Prototype Layout (Artisitic Rendition)

Fig A.1 – Contamination Probability per Continent

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List of Tables

Table 2.1 – World Bank Class Division

Table 2.2 – Target Countries

Table 2.3 – Major Global Contaminants

Table 2.4 – Summary of WHO and National Water Contaminant Guidelines

Table 3.1 – Anthracite Sizing

Table 3.2 – Membrane Energy and Pressure Demands

Table 3.3 – Ultraviolet Dosage Required

Table 3.4 – Activated Carbon Magnitudes and Applications

Table 3.5 – Water Contaminants that can be Reduced to Acceptable Standards by AC Filtration

Table 4.1 – Pugh Decision Matrix

Table 6.1 – Test Results

Table A.1 – Full List of Contaminants

Table C.1 – EIOLCA of Filter Parts

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Chapter 1 – Introduction

Motivation

Clean drinking water is essential to life. The UN Committee on Economic, Social and

Cultural Rights has declared it “indispensable for leading a life in human dignity. It is a

prerequisite for the realization of other human rights.”1 If article 25 of the Declaration of

Human rights stipulates that “everyone has the right to a standard of living adequate for the

health and well-being of himself and of his family, including food, clothing, housing and medical

care and necessary social services...”2 how much more the case for the very precursor of such

rights. Despite international recognition of its importance 884 million people continue to have

unsafe drinking water3. This, compounded with the of inadequate sanitation result in

approximately 5000 children’s deaths daily4

Global efforts are being invested to improve these statistics. Although solutions are

continuously proposed to remediate the issue, the best is not apparent. The process of

selection for the ideal treatment method is complicated by the individual scope of each option.

Varying target contaminants, geography, quantity and functional needs result in a

conglomeration of solutions each targeting a particular niche of the overall global problem. The

issue is exacerbated when producers of technology are insensitive to the needs of the

population that will be utilizing the proposed solution.

This team is interested in identifying the simplest solution for the largest geographic

populace. The quality of water to be treated, its source, and its use will be taken into

consideration. The supply quantity and its purpose (whether for direct consumption or other

use) are also key factors for consideration. It is also prudent to identify materials’ availability

and appropriate technology to employ for the construction and maintenance of said unit. It is

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the intent of this team to design small, easy to use, independent filtration units for individual

household use.

The project is commissioned by the Ontario Centres of Excellence’s Connections

Program’s industrial partner Mr. Richard Singh of Creative Engineering Services Inc. The interest

is academic in nature with the expectation of reproducing past experimental results for the

selected treatment option. Neither student involved in this thesis project nor the industry

partner have an intimate background of water filtration methods. The main body of information

provided in this document as collected via a thorough literature search is the basis for the

principles employed when designing and testing the filtration unit.

Objectives

The objective of this thesis is to establish a simple, effective and efficient water

filtration unit. Simple indicates that minimal education will be required to build, operate or

maintain the unit. Poor education can lead to inappropriate use, degrading the quality of

treated water. Effectiveness is expressed by the unit’s ability to reduce major contaminants

within the influent water to World Health Organization standards. The unit must be efficient in

both its energy and resource requirements during operation and maintenance. It must deliver

an appropriate amount of potable water for a family’s needs and be scalable to accommodate

for the variety of family sizes. An additional aim is to maximize the incorporation of local

equipment and materials for its production, thereby minimizing its costs (labour and

maintenance) and ecological footprint. Both are reasonable concerns when attempting to

provide an ethically responsible solution. Finally, the safety of the users and the environment is

of the outmost concern.

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The recommended method will be tested using a physical prototype to ensure both

feasibility of design and the desired flow rate are met. Additionally, construction will be used to

gage the ease of production and use, along with the expertise needed to maintain the unit.

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Chapter 2 – Water Consumption and Demand

Target Demographic

An understanding of the influent water issues and the target potable water quality are

necessary to isolate the technology best tailored to remove contaminants present. In the event

that water source analyses concludes localized water quality issues these will be ignored by the

method proposed. This is not to suggest that such problems are insignificant but rather to

admit that they fall outside the scope for a global water purifying unit. Furthermore, by

selecting a target demographic the water demands will be properly assessed.

The World Bank’s Income Class designation is a simple and quantitative means of

highlighting which populations are in greatest need of improved water treatment. World Bank’s

Atlas Method calculates the GNI (Gross National Income) for every country which is then used to

classify respective economies. “The Atlas conversion factor for any year is the average of a

country’s exchange rate... and its exchange rates for the two preceding years, adjusted for the

difference between the rate of inflation”5. In the event that the official exchange rate of a

country appears to be an unreliable means of tracking economic progress an alternate estimate

for the rate is used in the Atlas formula. Below is World Bank’s formula for the Atlas conversion

factor for year t.

and the calculation of GNI per capita in U.S. dollars for year t :

Once the normalized GNI is generated, national economies are classified as being:

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Table 2.1 – World Bank Class Division6

Economic CLASS GNI per capita

Low Income $935 or less

Lower Middle Income $936 to $3,705

Upper Middle Income $3,706 to $11,455

High Income $11,456 or more

For this thesis, countries belonging to lower middle income or beyond have been

targeted as possessing populations that will benefit from the incorporation of private filters at

the household level. This list does not assume an entire lack of water treatment infrastructure

but rather serves to highlight potential for inequalities of its distribution. Furthermore, by

highlighting this subset of the global population, a weighted average consumption rate can be

calculated as a target flow rate for the proposed unit.

Thus of 141 nations with an economic CLASS calculated by World Bank, seventy eight of

these have been targeted as benefiters (see Table 2.2). Based on this list, the domestic water

footprint7 of each of the identified nations was used in conjunction with the populations of each

to come up with a weighted average daily domestic water consumption estimate:

The target flow rate must meet the 86L/day per person in the household. This figure,

while large, meets the primary consumption requirements of cooking and drinking, and those of

secondary nature. These include but are not limited to: feeding private livestock, gardening,

personal sanitation and washing8. While not all of the population targeted for this product has

access to this much water, the goal is to design a unit that can handle larger water demands, as

well as seasonal fluctuations. The design’s scalability permits for smaller models to be made

wherever preferred.

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Target Contaminants

The World Health Organization has established drinking water standards for metals,

suspended ions, bacteria/virus, and other contaminants. Of these, some are especially

dangerous to human life while others can accumulate in the body degrading health over a

prolonged period of time. The filter must remove the contaminants found in drinking water that

pose an immediate danger to human health. It is desired that other long range contaminants be

minimized but is not an immediate objective. To determine which contaminants require

immediate removal, data provided by the UN will be used. The United Nations’ Global

Environment Monitoring System GEMStat Programme “ share[s] surface and ground water

quality data sets collected from the GEMS/Water Global Network, including more than 3,000

stations, close to four million records, and over 100 parameters.”9 and has been monitoring

global water table quality for over thirty years10. The data they have compiled is voluntarily

provided by participating nations. Samples from various water table sites are collected

anywhere from a monthly to annual basis. Some countries have been providing data at regular

intervals for several decades while others have been more sporadic in their samples submission.

Data provided has been assessed as “Safe”, “Threatened” or “Dangerous” for a variety of

contaminants:

Table 2.3 – Major Global Contaminants

Major Ions Metals Microbiology

Chloride Aluminum Arsenic Boron Coliform

Sodium Cadmium Iron Lead Faecal Coliform Bacteria

Sulphate Manganese Mercury Nickel

(see Appendix A for a full list of contaminants and their probabilities of occurance)

Data Analysis

GEMStat provided data organized by country, contaminant, year and number of samples

per test set. Sample set data was summarized by including the lowest and highest results, the

7

mean, median, and standard deviation of individual sets. Each sample set represents the

multiple tests conducted for that country and year. The United Nations’ Environment Program

(UNEP) has posted a table outlining the World Health Organization’s contamination standards in

conjunction with other major environmental organization’s protocols. The WHO’s guidelines are

thus used to determine the quality of the samples shared except for bacterial contaminants, as

universal standards were not provided for such specimens. In these circumstances Canadian

guidelines have been used instead. For a list of WHO and select National water contaminant

guidelines, refer to Table 2.4.

Wherever the maximum value of the set was above the permissible contaminant

threshold defined by WHO, that set’s water quality was flagged as “Threatened”. If the mean

was above the threshold, the water was classified as “Dangerous”. Using these simple flags, the

contaminant list (found in Table 2.3) was created from the much larger list of potential

contaminants.

While individual results on a per sample basis were not provided, the data proved useful

in diagnosing the general health of national surface water sources. The standard deviation of

sample sets has assisted in identifying trends within national levels. As such, wherever the

standard deviation exceeds of 100, it has been ignored in the figures generated for visualization

purposes. While the maximum result included is still useful in suggesting that that water suffers

from that contaminant, its extreme value with respect to the set’s minimum and mean, along

with a blatantly high standard deviation suggest that it is an anomalous sample, rather than

consistently repeatable. Fig 2.1, which shows Asia’s Iron contamination, indicates that there is a

consistently high level of iron in the water exceeding the permissible 0.2mg/L recommended

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guideline. Note, no data has been excluded from this graph on the grounds that the standard

deviation does not exceed 100.

Conversely, Africa’s Sulfate contamination data (shown in Fig 2.2) is generally consistent

despite the exclusion of 10 of the 81 sample sets. Since 500mg/L is the recommended

maximum quantity, this figure shows that Sulfate contamination is not a significant problem for

Africa (nor the Americas or Asia). Hence it has been eliminated as one of the priority

contaminants that must be addressed by our filtration unit.

Division of GEMStat Data

As information provided to GEMStat is not obligatory but rather voluntary, not all

populations have been represented equally via participation in the program. Despite this,

national and continental data collected have assisted in dividing the data by socio-economic

demographic (on a national scale). Fig 2.3 illustrates this population representation as adjusted

for population growth. First to note is the total representation of the continent. In the case of

Africa, less than 25% of the population has participated in GEMStat’s program. Of that that has,

it is almost an even split between developed and developing populations.

Also, not all nations currently considered developed by World Bank’s Atlas classification

have been so in the past 30 years. As development is an ongoing process, some nations may

have met the “developed” threshold used earlier in this thesis sometime during this period. In

other words, fewer countries or different nations were classified as middle to higher income in

the 1980’s than is shown here. With respect to population representation in the data, this

implies that poor populations have had a higher level of representation in statistics in reality

than is shown here. For the purpose of analyzing source water it is more important to show that

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sufficient data has been provided for representation than to show the divide between economic

classes.

Data Trends

A strong correlation exists between GEMStat’s data and that of the World Bank’s

economic class. The more developed a nation is, the greater the presence of major ions and

toxic metals. For developing nations, increased industrial growth contributes to added

environmental degradation through waste disposal. This thesis will focus on eliminating the

most dangerous contaminants affecting the most vulnerable water sources first. It is assumed

that treatment infrastructure will continue to be implemented and match added pollutants

introduced through increased industrialization. China and India represent a paradox in that they

are developing faster than their populace’s water issues are being addressed. Based on

conclusions drawn from the statistical analysis explained above, the elimination of

microbiological contaminants is the primary target of this thesis as these are most prevalent and

dangerous. “At any given time, almost half the population of the developing world is suffering

from one or more of the main diseases associated with inadequate provision of water and

sanitation.”11

Heavy metal and ion pollutants will be considered outside the primary scope of the

thesis project as they are particularly localized problems normally caused by few participating

countries with extreme conditions in very few sample sets provided.

Water Source

This thesis will focus on treating surface water tables. Surface water is readily available

from rivers and streams, lakes and rain water collected by individuals. It will not deal with

10

underground sources or salt water. Thus, desalinization technology and its application or the

method of collecting water will not be addressed here.

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Chapter 3 – Water Filtering Methods For the purposes of this project, filtration technologies have been organized in four

major categories: Granular Media Filtering, Barrier Media Filtering, Disinfection Treatments,

and Carbon Adsorption. These broad sections classify all eight filtration methods researched

and analyzed, by underlying technology employed.

Granular Media Filtering

Media filters employ basic principles for operation. The filter is made of a bed of

particulates which act as a physical barrier to strain the feed water. The feed water, which

contains suspended solids, passes through the filter bed grains of the media. The suspended

solids, however, are entrapped within the filter bed and strained out of the feed water. The

smaller the grains, the fewer and smaller the particles it allows through.

There are two major forms of granular filtration – slow and rapid. Rapid granular

filtering uses a pressure process to force feed water through the filter, whereas slow filtration

uses gravity to provide the necessary pressure. While slow filtering with sand has been used for

well over two centuries, it was not until the 1880’s and the study of bacteria that water

purification was subjected to systematic scientific analysis. Studies revealed that “when kept in

proper condition, *slow+ sand filters … took away as much as 98 percent of the bacterial

content”12. Since these filters operate at much slower filtration rates, a biochemical change is

able to take place in the upper layers of the filter bed which increases the filter’s effectiveness.

As the filtration process is carried out, organic particles previously suspended in the feed water

settle on the top layer of the filter bed. These particles begin to culture a bacterial “skin or layer

of slime”, and it is the “biochemical transformations *that+ occur in this layer … which are

necessary to make slow filters efficient as filters with biological activity”13. This layer is referred

to as the Schmutzdecke.

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[A] sticky film, which is reddish-brown in colour, consists of decomposing

organic matter, iron, manganese and silica and therefore acts as a fine filter

that contributes to the removal of fine colloidal particles in the raw water.

The Schmutzdecke also doubles up as an initial zone of biological activity,

providing some degradation of soluble organics in the raw water, which is

useful for reducing tastes, odours and colour14.

The Schmutzdecke is generally defined as the top 0.5 – 2cm of a slow filter. The bacteria

that form in this layer use the filtered organic matter as food. A portion of this is oxidized to

provide metabolic energy while the rest is converted into cell material that supports their

growth15. To do so, the sand must be kept wet and the filter layers must remain undisturbed by

turbulent feed waters which can otherwise disrupt bacterial growth.

What occurs below the Schmutzdecke while imperative to the success of the

purification processes that occurs in slow filters is poorly understood.16 It is speculated that a

combination of temperature conditions that impede growth, lack of organic matter to meet

nutritional needs, the presence of various types of predatory organisms (protozoa and lower

metazoa) and of various microorganisms that produce chemical or biological poisons, all

contribute to the control and limiting of intestinal bacteria. Thus this combination of factors in

the biological zone contributes to a “substantial reduction in the number of E. Coli, and an even

greater proportional decrease in pathogens”17.

Sand

Sand is the most popular material used in granular media filters. Gravel, also loose rock

but larger than 2mm in diameter, will be explained in conjunction to its finer counterpart. The

specific size range of gravel is 2-4mm18, while geologically classified sand is 62.5µm to 2mm in

diameter19. Sand’s advantages as a water filtration media include its widespread availability,

variation in size, inertness, minimal cost (if any), and lack of processing requirements. Silica

sand’s availability and inertness make it the most favourable choice. Some suggested variables

13

for consideration when designing filtration systems using sand include the particles’ effective

size (the average particle diameter) and the depth of the filter bed. For fine sand (0.4-0.8mm)

filter bed heights should range between 18 and 36cm. At such conditions, filtration rates of 80-

400L/m2-min are achievable for heavy influent rates20. Such rates are common in large

wastewater filtration plants. On a smaller scale such as that of this thesis, slower rates are to be

anticipated. Notice that the filtration rate is a relative measurement dependent on the filter’s

surface area.

Despite the initial concern that a slower filtration rate is undesirable, upon closer

inspection it may prove to be advantageous. Slower flow rates allow greater opportunity for

pollutants to come into contact with the filter media and become entrapped in a layer. Slower

filter rates also permit biological activity to aid in the destruction and removal of undesirable

biotic contaminants as explained earlier. Hence as long as the flow rate still meets family water

needs, slower is better.

Some of the disadvantages of the sand media filter, common to media filters in general,

include the need to backwash. Backwash frequency is dependent on the quality of incoming

water, and flow rate experienced relative to that of the filter performing at optimum conditions.

Backwashing is a water intensive process that requires several litres of clean water that must be

disposed of upon use. Furthermore, as with other gravitational media, the sand filter must

undergo a ripening stage preceding its first use and after each backwash cycle21 for the

Schmutzdecke’s development. During this ripening, water that initially flows through the

system will not have its bacterial contaminants removed and hence should not be used for

human ingestion. Finally, the biotic layer is very sensitive to disturbances and users must ensure

that turbulent water or fluctuating flow rates are minimized.

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Anthracite

Anthracite is another granular media filter option. It is the naturally occurring

“intermediate formation between bituminous coal and graphite” with a 92 to 98% carbon

content22. It is denser than bituminous coal and has low volatility23. Its high combustion

temperature (>925˚C)24 means it is unlikely to combust under standard conditions, thus allowing

for safe storage. Its largest reserve is found in the Pennsylvania Coal Region, but other large

sources include mines in Austria, Canada, Denmark, Finland, Germany, India, Italy, Japan,

Netherlands, Russia, Sweden, Switzerland, and Turkey25. Despite having weak electrostatic

properties that can aid in trapping particulates in the water in the same manner that activated

carbon employs, its significantly smaller surface area and lack of processing after mining, make it

more suitable as a sediment filter like sand. Its advantages include the range of particle sizes

available26:

Table 3.1 – Anthracite Sizing

Classification Chestnut Pea Buckwheat Rice Barley

Min Size (in) 7/8 9/16 3/8 3/16 3/32

Max Size (in) 1 1/2 7/8 9/16 3/8 3/16

As such, it can easily be selected for a particular desired diameter and a gradient of

different sized anthracite layers can effectively trap very small pollutants. An ideal particle

diameter to filter bed depth ratio for one layer of anthracite is an effective size of 0.8-2mm in

diameter and a depth of anywhere between 36-90cm and dependent on the quality of incoming

water27. Whenever designing gravitational filters, the depth of each filter layer and the particle

size must be considered to minimize head loss. If the drop is too quick, pollutants will remain in

the uppermost levels, inhibiting deeper penetration of the water and ultimately requiring

frequenter backwash to improve flow.

15

Like other filter media, anthracite is not effective in removing chemical pollutants

present in the water supply. Despite it being a commonly found natural resource, anthracite is

not necessarily mined in the remote areas populated by the target demographic. Furthermore,

mining is an energy intensive practice with damaging effects to local ecosystems. Finally,

according to one site, a kg of anthracite costs eight dollars US, not including shipping and

handling28.

Anthracite is nontoxic when ingested, and only a mild mechanical irritant if the dust

comes into contact with eyes or skin29. “Excessive, long term inhalation to coal dust may cause

pneumoconiosis (or “Black Lung”)” which includes “reduction in pulmonary function, pulmonary

hypertension, bronchitis, emphysema and premature death”30. While users of the filter and

those who will provide maintenance are not inherently exposed in such a manner, it is

important to be aware of the consequences of misuse when assessing the overall impact of the

material.

Barrier Media Filtering

Barrier Media Filters, as the name suggests, utilize techniques that involve a physical

obstruction in the path of flow. Unlike Granular Media Filters which are loose particle based,

these use a solid permanent, porous obstacle to trap contaminants smaller than the pore size of

the filter.

Membrane Technology

Membrane filtration technology is little more than a sophisticated sieving process,

relying on a pressure or vacuum to drive the process. Rather than use a loose particle media to

entrap suspended solids, it employs an engineered barrier in the form of a porous material. The

16

effectiveness of the membrane is directly determined by the size of the pores like its

counterpart31. There are two different operating processes for membrane filtration.

The first process, Dead-End Filtration, has one flow entering the filter, and one flow

exiting. In this method, all of the incoming flow (the feed water) encounters the membrane and

is forced to pass through the membrane. Any suspended solids in the feed water too large to fit

through the membrane’s pores are deposited on the surface of the filter. While the simplest of

the two processes, it is also more susceptible to membrane clogging. The build up of particulate

on the membrane is steady and extremely short in comparison to the membrane life. As

expected, build up that gathers on the membrane, the slower the filtration rate achieved. To

restore the Dead-End Filtration throughput relatively frequent backwashing to clear the filter of

accumulated contaminants is necessary. The frequency of backwashing is determined entirely

by the turbidity of the feed water and its flow rate through the filter. In very demanding

commercial applications involving large volumes of water, backwashing is necessary every 15-

60mins32. Unlike media filtration however, backwashing a membrane filter is quick, highly

effective, and restores the filter to its full capacity33.

The second operating process for membrane filtration is Cross-Flow Filtration. The

Cross-flow Filtration method seeks to avoid the problem of built up of particulate on the

membrane. In Dead-End Filtration, the feed water is delivered perpendicular to the membrane,

forcing the feed water through the membrane while depositing any suspended solids on the

pressure side of the membrane. In contrast, Cross-Flow filtration does not force the particles

into the membrane. One flow enters the filter, and two exit – one on the feed water side of the

membrane, and one on the opposite side.

17

Feed water enters the filter and is passed parallel to the membrane at high velocity.

The momentum of the majority of particulates carries them along the surface of the membrane,

and out the exit as part of the retentate (waste water that has a high concentration of

suspended solids). The feed water that is drawn through the membrane thus has a significantly

lower concentration of particles. Any of these particles that are drawn to the membrane are

trapped by the membrane and then most are subsequently freed by the high velocity water

above them. These too are henceforth carried along the membrane and out the exit as

additional retentate. A larger portion of the feed water is thus able to cross through the

membrane with less build up and clogging of the membrane34. The two exit streams are

classified as follows: (1) the Retentate, high in concentration of suspended solids; and (2) the

Permeate or filtered solution that has been filtered of suspended solids. This process is shown

in Fig 3.1. With this method, there is still some build up on the membrane, and backwashing will

eventually be necessary, but the duration of the filtering cycle between each backwash is

significantly increased, as is the volume of permeate produced.

Membranes for drinking water production are generally manufactured from synthetic

polymers to reduce costs. These polymers may be any of “a wide variety of materials, including

Cellulose Acetate (CA), Polyvinylidene Fluoride (PVDF), Polyacrylonitrile (PAN), Polypropylene

(PP), Polysulfone (PS), Polyethersulfone (PES), or other polymers”35. Ceramic, metallic and

organic membranes are other options but lack the manufacturability and durability of the

polymeric membranes. Material choices are often based upon strength as large commercial

operations may be required to operate at pressures as high as 85-100kPa36. For this thesis,

strength will be ignored as the filter is unlikely to operate under high pressure.

18

One of the greatest benefits of using membrane filtration is the length of life of the

membrane itself. The technology is robust enough that it can withstand years of use and its

simple maintenance requirements make it a desirable filtration option:

When membranes no longer produce clean water at the desired rate, they

are cleaned in place with soap and water and returned to service.

Membranes can be repeatedly cleaned for years of productive, dependable

service prior to replacement”37.

There are four main forms of membrane filtration, classified based on the size of the

pores of the membrane:

1) Microfiltration (MF) uses pressure-driven membrane filtration. Pore size: 0.1-0.2µm

2) Ultrafiltration (UF) uses pressure-driven membrane filtration. Pore size: 0.01-

0.05µm

3) Nanofiltration (NF) also a pressure-driven membrane filtration and uses some of the

principles of reverse osmosis. Pore size: ~0.001µm

4) Reverse Osmosis (RO) a process that uses pressure to force the migration of the

water from one side of the membrane to the other. Pore size: 0.0001µm38.

The effectiveness of these filtration methods with respect to pathogen removal are

shown in Fig 3.2. Effectiveness improves with a decrease in pore size but this is associated with

increased pressure demands. As technological advancements in membrane technology

progress, new designs opt to minimize the pressure needed for effective particulate removal.

As Fig 3.2 shows, such filters are also highly successful in removing protozoan, oocysts, helminth

ova, and bacteria/viruses39. Reverse Osmosis filters can even remove dissolved constituents,

NDMA(N-Nitrosodimethylamine) and other related organic compounds. The ability to filter

while simultaneously disinfecting avoids the need for subsequent disinfection treatment.

Membrane technology’s mechanical method of disinfection also prevents the opportunity for

19

microbial resistance to chemicals to develop. Additionally, metal salts (iron or aluminum) can

also be added to the process to increase the filters’ performance40.

There are three common membrane modules: Tubular, Spiral Wound, and Hollow Tube.

Tubular membranes are cylindrical in shape (ranging from 5-15mm in diameter) and arranged

lengthwise inside a tube. Feed water enters the tubes from within and is forced through the

cylinder walls. Due to the size of the cylinders, clogging is very rare41. Spiral wound membrane

filters act very similar to Cross-Flow filters mentioned earlier. They are manufactured as flat

sheets and then rolled into compact spiral shapes. As the feed water passes through the length

of the roll, some passes through the rolled up membrane layers depositing contaminants on the

membrane. This permeate flow is diverted along the spiral to the centre where it is collected in

a pipe that exits the filter carrying the cleaned water. The remainder of the flow and residue

exit out the other side of the roll42. Hollow membrane filters function similar to Tubular filters.

The main difference is the diameter of the cylindrical fibres which is on the order of 0.1µm and

less. As such, the filtered water quality can be extremely high. They are, however, very easily

clogged and are therefore generally limited to uses in which the feed water already has a low

suspended solids content43.

The reader must keep in mind that these units are not standalone. All membrane filters

require water be pre-treated to avoid fouling. They also require a constant supply of electricity

to drive the pumps necessary for the pressure differences used to remove pollutants from the

water, although MF is possible without any pump work. Maintenance workers will need to

handle residual waste and be prepared to properly dispose of the concentrate. Finally, such

technology currently lacks a cheap and reliable method of monitoring the exit water’s quality.

In the specific case of Reverse Osmosis filters, these are best used for groundwater/low solids

20

surface water and are expensive compared to conventional treatments (including micro and

ultrafiltration)44. Table 3.2 outlines the minimal energy and pressure demands for the various

membrane filters available. Such filters cannot be easily manufactured locally. The

transportation and technology costs cannot guarantee affordability on a per household basis.

The intensity of the filtration process is better suited for larger projects and so has potential for

community sized filtration plants used in the future.

Ceramic

Ceramic like other barrier filters relies on its effective porosity to trap particles larger

than its pore size. Usually, the ceramic is clay formed into a pot shape before fired up. The

benefits ceramic based filter media include its low cost, material availability, and easy

maintenance. Ideal clay for the filter is that of clay castoffs from local brick factories that have

not been fired up45. Such clay has been aged for several weeks and has improved porosity that

fresh clay lacks.

As part of the manufacturing process, potters are suggested to add sawdust or rice hulks

to the clay mixture. Once fired up, these materials burn off, leaving behind a regular, even pore

distribution in the material46. It is imperative that once the clay has been formed and fired, the

sides of the pot not be handled as the oils from workers’ hands can deposit dirt that inhibits the

optimal performance of the filter while at the same time allowing for potential bacterial

contamination of the water once the filter is set up47. A layer of colloidal silver is painted on the

inside of the pot. The silver ions kill approximately 99.88% of bacterial and viral pathogens

found within the tainted water source by disrupting their respiratory function48.

Since these filters are relatively simple and easy to make locally, they can be

manufactured at an exceptionally low cost, with some estimates as low as $4 US (2005)49. To

21

ensure that filters are working at optimal performance, the interior needs to be scrubbed

approximately every six months to remove built up residue50. While such filters are cheap and

easy to manufacture, they lack the ability to remove chemical toxins from water. Furthermore,

delicate handling of the pots is imperative to prevent cracks from developing prematurely which

will render the filter useless. Likewise, they lack redundancies to ensure that the water leaving

the filter is truly potable.

Overall manufacturing requirements include a cement mixer and grinder to process the

aged workable clay, colloidal silver which can either be purchased or manufactured through

electrolysis, rice hulks, sawdust or similarly cheap, fine, combustible particles to create the

necessary pores within the filter, and a kiln/cooling area. Workers can be trained to properly

manufacture and maintain the filters51.

Concrete

Concrete is a mixture of cement, fly ash, slag cement, various aggregates (such as gravel,

limestone or granite), water and potential chemical admixtures (CaCl2, NaCl, C6H12O6, or

plasticizers)52 and is used as another cheap, simple to manufacture barrier filter. Aggregates

and admixtures are responsible for the various properties of concrete including its porosity and

resistance to corrosion. Furthermore, like ceramic, concrete can be formed into various shapes

and solidified. Unlike ceramic this does not require intense heat but rather the addition of

water.

Cement is slightly hazardous for workers, as unsafe exposure to the fine particles can

cause respiratory problems if inhaled. Individuals may also suffer from cement burns or skin

inflammation due to allergic contact dermatitis53, finally heavy cement filters need to be

carefully transported to avoid injury.

22

As with ceramic filters, care must be taken to ensure that concrete filters are not

delivered cracked. They must be monitored for chemical corrosion to prevent potential leaks in

the filter. Fortunately, as with ceramic, these can be gently cleaned by scrubbing away the dirt

film that has developed. However, unlike ceramic, these filters only trap larger particles and

improve the turbidity of water. There is no bacterial/viral or chemical process to treat the

water; thus concrete can only be used as an intermediary filtration step where water will need

further treatment. Finally, the filter will need occasional drainage to remove dirt build up. Both

cement and ceramic filters naturally cool the water as it sweats through the media.

Disinfection Treatment

This subsection contains processes that attack bacteria and other living organisms.

These processes are most commonly chemical in nature, however, can include methods such as

Ultra Violet Radiation, which is discussed here as well. Of note, because disinfection treatments

are aimed solely at neutralizing bacterial and viral threats, they are usually a secondary form of

treatment that is preceded by some form of filtration aimed at eliminating particulate matter

from the feed water.

Ultraviolet Radiation

As the name suggests, ultraviolet bulbs are used to disinfect contaminated influent

passing by. “The germicidal properties of the radiation emitted from ultraviolet (UV) light

sources have been used in a wide variety of applications since its use was pioneered in the early

1900’s”54. There is an effective range of electromagnetic radiation which destroys a large

number of bacterial and viral contaminants commonly plaguing drinking water. The optimum

intensity range of effective electromagnetic radiation is between 250 and 270nm, with the

consumer standard set at bulbs with an intensity of 245nm55. Table 3.3 lists common pathogens

found in drinking water and the necessary UV dosage at 245nm to render them innocuous56.

23

The Tobacco mosaic virus requires the largest dosage of 440,000 µW-s/cm2, this

translates to needing 0.44J of energy per square centimetre of water that crosses the UV

barrier. With such small dosages required, UV light can be pulsed at short intermittent times to

disinfect the water, thus conserving energy in the process. Mere seconds of UV exposure

effectively treat visually clear water as water flows past a UV light chamber housing the UV bulb

and its necessary components, while UV light is emitted killing 99% of the listed pathogens57. At

no point in time does the water actually come into contact with the bulb or other equipment, it

simply passes by a UV transparent chamber.

The benefits of using ultraviolet radiation as a sanitizer include the method’s

effectiveness regardless of the water’s temperature and pH level. There is no need to store any

hazardous materials as is the case with chemical disinfection. Furthermore, no Volatile Organic

Compounds (VOCs) or toxic air emissions are produced in the process, there are no known toxic

or non-toxic by-products, and there is no danger of overdosing on the dosage of UV energy that

the water is exposed to58.

As the use of UV bulbs requires energy, there is a need for a stable, high voltage supply

of electrical power. Microbial factors, such as type, source, age and density of the water, along

with chemical factors such as the presence of nitrites, sulfites, iron, the water’s hardness, and

aromatic organic levels will all impede the disinfector’s performance59. UV radiation acts as a

“point disinfectant”. It kills pathogens that happen to pass by the UV chamber when activated.

If however, pathogens manage to escape breed further down the system, UV treatment

provides no protection against re-infection downstream60. This type of treatment requires

frequent monitoring by trained staff and is better suited for large filtration systems. Scheduled

maintenance and frequent testing of the bulb intensity and water quality are necessary to

24

ensure that the bulbs are effectively penetrating deep enough within the passing water supply

to treat the entire volume. As time passes, debris and pollutants may deposit themselves

against the bulbs’ housing, inhibiting the UV rays from destroying the pathogens by blocking

their path.

This type of treatment requires a minimum of two bulbs, that are pulsed energy, broad

band xenon; narrow band excimer or continuous band mercury, to ensure that even if one is not

operable or is being replaced the other can continue to disinfect61. Mechanical wipers for

optimal transmission between cleaning and maintenance work are beneficial. Photodiode

sensors monitoring the intensity of the UV energy supplied to the interior of the water supply

aid in detecting any changes to the dosage supplied. Also required are quartz sleeves with

appropriate transmission rates, and safety controls that will automatically shut off the lamps

when functioning at high bulb temperatures and dealing with low flow levels62. Finally, ballasts

used to supply regulated power are required and come in three forms: standard (core coil),

energy efficient (core coil) or electronic solid state63. Such complicated parts clearly suggest

that this is a much more sophisticated and demanding purification process than is applicable for

intended customer. Other maintenance demands include cleaning of the UV chamber at least

every six months, and that calcium levels, turbidity, and colour be observed to ensure that these

factors do not hinder the performance of the bulbs64.

Chemical Purification

Chemical purification relies on chemical reactions to drive the disinfection process. Its

advantages include its effectiveness, lack of energy requirements, and ability to support fast

flow rates within a water treatment system. Its disadvantages may outweigh its benefits and

warrant it impractical as a process for individual household purposes. These include the

expensive and ongoing need to purchase treatment chemicals, the complicated nature of

25

delicately balancing the additives to obtain the correct quality of water while not exposing

drinkers to harmful levels of toxins, the potential for incorrect handling and disposal of the

chemicals and their waste which can threaten both human and environmental safety, and the

inability to improve taste and some physical characteristics of the water (such as turbidity)65.

There is a long list of potential chemicals that can be added to treated water to disinfect

the supply. These are broken up into two categories: coagulants and precipitants. Coagulants

are involved in the “chemical destabilization of particles and in the formation of larger particles

through perikinetic flocculation (collection of particles in the size range from 0.01 to 1µm)”66.

Precipitants are chemicals added “to alter the physical state of dissolved and suspended solids

and facilitate their removal by sedimentation”67. Both cases need contaminants strained or to

sediment out of the flow water. The following is a list of popular coagulants and precipitants:

Alum, Aluminum chloride, Calcium hydroxide (lime), Ferric chloride, Ferric sulfate, Ferrous

sulfate, and Sodium aluminate. Precipitants to remove heavy metals and dissolved organic

substances include Cadmium hydroxide, Cadmium sulfide, Chromium hydroxide, Copper

hydroxide, Copper sulfide, Iron II hydroxide, Iron III sulfide, Lead hydroxide, Lead sulfide,

Mercury hydroxide, Mercury sulfide, Nickel hydroxide, Nickel sulfide, Silver hydroxide, Silver

sulfide, Zinc hydroxide, and Zinc sulfide68.

Chemical exposure to above mentioned acids and bases can lead to dangerous skin

burns, and irritation of mucosal linings. Many are known mammalian cell mutagens and high

exposure to any can cause death69. Finally, as these chemicals are not necessarily available

locally, there is the impractical need to have them delivered, a large deterrent for employing

this technique in remote regions of the world.

26

Carbon Adsorption

Adsorption is the binding of molecules or particles to a surface. These binding forces

are generally very weak, reversible, and can attract almost anything of appropriate size that is

dissolved or suspended in a solution (in the case of water filtration). Compounds with stronger

colour, taste and odour tend to bind the strongest70. While there exist many materials that can

be activated such as alumina, silicas, zeolites, clays, polymers and even biomass activated

carbon (AC) has the strongest physical adsorption forces, per volume of adsorbing porosity, of

any known substance 71. This ability to adsorb is due to its great surface area. AC can achieve

surface areas of greater than 1000m2/g when activated properly72.

The adsorption process is based largely upon the ratio of the concentration of the

particulate to its solubility in the mixture. In general, adsorptivity is understood to depend on

five factors:

1) Physical properties of the AC (pore size and distribution). Filtration is best when the

pores are slightly larger than the contaminant molecules.

2) The chemical nature of the carbon source (amounts of hydrogen and oxygen

associated with it). “AC materials formed from different activation processes will

have chemical properties that make them more or less attractive to various

contaminants”73.

3) The chemical composition and concentration of the contaminant. There is a

tendency for AC to form the strongest binds to organic molecules, likely because the

chemical nature of organic molecules and AC are very similar.

27

4) The temperature and pH of the water. As pH and temperature decrease organic

chemicals occur in more adsorbable forms.

5) The flow rate and the amount of time it is exposed to the feed water. Since carbon

adsorption is based largely on physical contact of the contaminant with the AC, the

longer the exposure of the AC, the more effective the filtration.

Activated carbon is essentially a crude form of graphite. It has a very porous, imperfect

structure that enables it to adsorb a broad size range of compounds. AC can be produced from

a wide array of materials including: wood, coal, peat, coconut shells, saran, and recycled tires74.

Material differences result in variations of the distribution of internal pores, affecting the

surface of the carbon and therefore its ability to adsorb75. Additionally, alkali ash content of the

final product varies depending on the base material which can increase the pH of the filter,

hindering AC’s ability to adsorb organic chemicals76. These values can range from 2 – 25%, with

the average falling at around 7%77. Ultimately, the microscopic structure (pore sizes and overall

surface areas), surface quality, and chemical composition can drastically change the

performance of the filter78.

While activation is relatively uncomplicated, the technology required in producing

consistent AC needs to be capable of maintaining strict quality control79. Production and

processing techniques for AC are dependent on the nature of the base material and the desired

characteristics. The most common production techniques used are Chemical Activation and

Steam Activation. Chemical Activation is used largely for organic base materials such as wood

and peat which “is impregnated with a strong dehydrating agent ... mixed into a paste and then

heated to temperatures of 500 – 800˚C ... the resultant activated carbon is washed, dried and

ground to powder”80. Steam Activation is used when coal and carbonized coconut shell are the

28

base materials. The activation process is carried out at 800 - 1100˚C in the presence of steam81.

As gasification of the material with steam occurs, the produced carbon monoxide and hydrogen

are burned off leaving the porous particles behind. This AC is then graded, screened and de-

dusted. Carbon produced by Chemical Activation tends to be very macroporous (containing a

wider pore structure) and this is ideal for adsorbing larger molecules. Carbon produced by

Steam Activation tends to be either microporous or mesoporous (containing finer or medium-

sized pore structures) better suited for adsorbing suspended compounds within liquids and

vapours82.

Activated Carbon particles can be produced in varying sizes:

Table 3.4 – Activated Carbon Magnitudes and Applications83

Granular Activated Carbon (GAC)

Powder Activated Carbon (PAC)

Pellet Activated Carbon

Typical Particle Sizes (mm)

0.20-5.00 ≤0.18 0.80-5.00

Typical Applications

Liquid and Gas phase Liquid Phase and Flue Gas Treatment

Gas Phase applications (lower pressure drop, higher mechanical strength, low dust content)

Activated Carbon has been shown to be able to remove several organic, and inorganic chemicals

to meet EPA Health Advisory Levels. These include Trihalomethanes, Pesticides, Industrial

Solvents (halogenated hydrocarbons), Polychlorinated Biphenyls (PBCs) and Polycyclic Aromatic

Hydrocarbons (PAHs)84 as is shown in Table 3.5.

However, activated carbon is ineffective for removing microbes, sodium, nitrates,

fluoride and hardness from water sources. Also, lead and other heavy metals can only be

removed by very specific Activated Carbon filters.

29

Chapter 4 – Technology Assessment

Method Selection Given that each of the methods described above has its respective strengths and

weaknesses, an organized means of selecting the most appropriate technology is necessary. A

common set of criteria was used to evaluate each method. These criteria have been organized

into subcategories as follows:

1. Parameters: this is a loose category describing the physical properties of the unit.

These are represented by the size of the unit, its anticipated flow rate, and the unit’s

storage capacity. Effective technology should not be insensitive to the need for

adequate unit storage. It must meet the 86L/day per household member requirement

specified earlier.

2. Life: is the qualitative precursor of the more detailed Life Cycle Analysis that will be

conducted for the chosen filter. Exotic material use, high maintenance demands

reflected in frequent and/or energy intensive processes, and the difficulty of use are to

be avoided.

3. Effectiveness: the major contaminants identified using GEMStat’s data must be reduced

to WHO standards with the basic expectation of large particulates removal, and

improved clarity, taste and odour of water.

4. Health Risks: the health risks associated to those making the units and using them. This

includes the manufacturing, use and disposal stages of the unit. The materials

themselves may be hazardous to health if inappropriate exposure occurs (as with

chemicals or radiation). Likewise, the technology to make the unit may incur a degree

of danger, (ex. Use of power tools).

30

5. Environment: anticipated damage to the environment during production, use, and end

of life are points of concern. Introducing a method which demands the disposal of

hazardous material (for example) would be insensitive to the already delicate conditions

of the environment that it is being used in. Furthermore, such degrading material or

technology can adversely affect the water quality of the site demanding more elaborate

treatment practices not necessarily accessible by the target demographic.

A Pugh matrix was developed with these five subheadings to compare the eight

treatment methods (Table 4.1). The weights provided are out of a cumulative 100% based on

level of importance as defined by the team for the overall success of the project. Some

properties, such as the size of the unit were considered less important than its effectiveness at

eliminating microbiological activity, the one being more aesthetic in nature than the other. The

ratings for each property were 1-8 where one was the least favourable and eight the most. The

original shows the weight assigned compounded with the raw score to create a weighted

average. The scores were then ranked, best being assigned first place and so forth.

Thus sand filtration has been identified as the best method for addressing the water

quality issues for the largest population while minimizing environmental and health risks

associated with its use.

Slow Sand Filtration Improvements

The main focus thus far has been upon the principles underlying slow sand filtration

technology, with little consideration given to any method that optimizes its function. There are,

in fact, several ways that the quality of the filtration can be improved, and the flow rates

increased. Filtrate quality is dependent upon a large variety of control factors including grain

size of the sand, quality (turbidity) of the influent water, amount of hydraulic loading (pressure

31

head of water above the filter bed), depth of the filter bed, and temperature of the filter. By

manipulating these control factors, one can optimize a filter to perform best. As will be

discussed, the quality can be further increased through the application of select pre-treatment

methods, use of metal-oxide sand, sand that has been pre-seeded with select microorganisms,

or through use of a sand-anthracite mixture85. For the purposes of this thesis project, only the

first improvement mentioned will be considered in-depth (select pre-treatment methods), also,

an improvement upon slow sand filtration is here defined as a change to the filtration process

that will improve either water quality or flow rate, without any sacrifice to the other.

Attempting to vary some of the control factors to optimize a filter may prove to be very

arduous task. For example, filtration rates are largely dependent upon the size of the sand

grains used, as is evidenced by Darcy’s Law for fluid flow through porous media (See Appendix B

for the equation and its derivation). This equation shows the proportional relationship between

the size of the grain and the filtration rate, namely, the smaller the sand grain, the lower the

hydraulic conductivity of the filter bed and the lower the filtration rate. While it may seem

prudent to improve the filter performance by increasing the filtration rate by increasing the size

of the grain, this degrades the quality achieved by the filter. For effective filtration, it is

necessary to use sand in the range of 0.23-0.60mm, because small grain sizes are important for

trapping suspended solids and organics in the influent water86.

Similar trade-offs would be necessary if one were to drastically change any of the other

aforementioned factors. For example, flow rates can be increased by changing the pressure

head above the filter bed (using a greater height of water), but this can drive the organics that

feed bacteria deeper within the filter, and stimulate growth that can adversely affect the quality

of effluent water87. The complication of dealing with these factors is echoed by the work of

32

Huisman & Wood, who wrote that “so many variables govern *the bacterial growth and filter

performance] ... that it is virtually impossible to make predictions, except on the basis of

previous experience with the particular water concerned”. There must be a simpler means of

improving filter performance. One such method is through pre-treatment.

Pre-filtration methods include: screening (the use of a mesh to remove larger

particulate and organic matter), reservoir storage (in large, open reservoirs for lengthy periods,

to facilitate the growth of bacteria causing pathogen breakdown), sedimentation storage (in

smaller quantities and for shorter time scales, to encourage larger particles to sediment), pre-

conditioning (addition of chemical to precipitate out salts), pre-chlorination (as a form of

sterilization), pH adjustment, flocculation, and the addition of coagulation agents (to encourage

smaller particles to precipitate from the water). When used in conjunction with slow sand

filtration, only two methods (screening and sedimentation storage) are applicable to the

objectives of this thesis. While there are many benefits to large reservoir storage, it is not

applicable in every situation, as it is best suited for the sides of rivers.

Pre-conditioning and pH adjustment are very useful processes for helping control the

chemical characteristics of the water before it reaches the filter. These processes are, however,

costly to implement and run since they depend on a supply of chemicals (such as lime, soda ash,

hydrogen chloride, or carbon dioxide) that are not locally available in most regions of the

world88. Additionally, these processes are not easily adaptable to individual household use and

are better for large-scale water treatment processes. A similar argument can be made for

flocculation and coagulation, which are most effectively applied to large operations. Most

importantly though, in the case of slow sand filtration, these two processes are not

33

recommended to be used as pre-treatments because floc carryover into the filter will very

rapidly clog the filter bed89.

Screening is a very simple process whereby a mesh is used to sift out larger particles,

such as leaves or twigs, and organics from the water that can otherwise clog the filter. Although

simple, this process can significantly ease the burden on the filter, improving run times between

necessary cleaning and the filter’s effectiveness. This process is generally not necessary for

groundwater sources since they are not likely to be contaminated with debris. It is, however, a

suggested pre-treatment method where applicable because both its construction and

implementation are very simple. The mesh can be made from a simple string grid or loosely

woven cloth hung over a wood frame which can be used to stir up and skim the water.

Alternatively, it can consist of a simple piece of fabric at the top of the filter through which the

water is poured, effectively straining out much of the larger particulate in the water.

Sedimentation storage can also be advantageous for the same reason. If the water is

stored and not perturbed for a period of time before being put through the filter, the heavier-

than-water particles will begin to sediment and collect at the bottom. In municipal and large-

scale water purification operations, this is advised to take place for at least 4 hours, however,

for application on a smaller scale (likely in buckets and jugs of volumes 20L and up) the

sedimentary process will be much quicker due to the shorter distance the particles can drop90.

Of note, the time-frame of these processes will be largely dependent upon the turbidity of the

water, with more turbid waters requiring more time to sediment. Lastly, while it is possible for a

sample of stagnant water undergoing the sedimentary process to begin culturing bacteria, this is

unlikely as it would require time on the order of days, rather than hours.

34

Life Cycle Analysis

The Economic Input Output Life Cycle Analysis is a useful tool in comparing multiple

options for the same problem or determining which stage of the process/object’s life (be it pre-

during manufacturing, use or end of life) is the most energy and pollution intensive and

problematic. For recommendation purposes, existing model currently manufactured and in use

has been analyzed. Biosand’s filter and mould designs which use the Schmutzdecke as part of

the treatment process is a sand filter encased in a long cylindrical column with a PVC pipe exiting

from the bottom and brought along the side of the column to a height a few inches above the

interior sand layer. This ensures the pressure gradient keeps the Schmutzdecke layer moist.

The unit’s individual components have been priced in current USD and converted to 1997 dollars

using the Consumer Price Index to conduct the EIOLCA. Of all the models provided by The

Green Institute of Carnegie Mellon University (including the University of Toronto’s/ Statistics

Canada 2002 model), the US Department of Commerce Industry Benchmark 1997 was selected

as it is the most detailed (divided into 439 consumer sectors)91. The greater definition of each

sector allows for a more accurate assessment of each component in the LCA.

Using BioSandFilter’s prescribed dimensions, their filter has been calculated to costs

$5.59 2008 USD. This cost includes all needed equipment and materials, transit and labour

according to US industry standards. As is explained later it has an appreciable service life of

several decades. The concrete encasing the sand filter mould needs cement, sand, ballast

(gravel 8mm to 30mm in diameter), PVC 1/2” tubing and elbows, cooking fat, steel sheets, nuts

and bolts, and steel shafts. Please refer to Appendix C for a detailed part listing and the

complete EIOLCA which includes environmental products produced in the process.

The mould outlined by BioSandFilter can create multiple filters. Thus the overall LCA is

for the production of 1000 individual water filters over its lifetime. This number reflects the

35

durability and longevity of the mould while recognizing that individual communities do not

normally exceed a thousand families.

The equipment needed to produce the mould should be available in urban centres close

to said communities. In the event that drills, grinders, lathe, rolling, and welding machines, are

scarce, the mould will have to be manufactured elsewhere and transported to the area of need.

Such additional costs have been incorporated in the EIOLCA as they cannot be accurately

estimated.

Premanufacture

Two important conditions must be met for the success of the filter’s use. The first is

ensuring families have access to said technology/units. The other, is proper education of users.

Before, and while making the filters, users must understand:

1. The purpose of the unit

2. How to properly care for units

3. When units are most effective at treating water

4. How to dispose of the unit once it becomes obsolete through physical damage or

improved water infrastructure and treatment

5. The limitations associated with the unit

Helping distribute the education and materials/equipment required to make the filters

will prove inadequate in correcting water quality issues faced by users until these points are

internalized.

36

Manufacture

The process of creating the filter moulds and units themselves may vary due to material

and equipment limitations. The mould can be made in towns that have the necessary

equipment and then shared amongst outlying villages to make the units. As the filter is made of

concrete it is difficult to transport once made and hence this concern should be responsibly

considered before manufacturing commences. Transportation should be minimal, safe for

workers, and minimize filter damage by cracks, clogging, or exposure to contaminating agents.

The mould itself is handmade. It is imperative that no dents exist within the inner core

piece as this will make it impossible for removal once the concrete has set92. It takes 25-37

hours for the concrete column to properly harden93. The unit should set for at least 7 days

before being transported94.

While the concrete encasement is made, sand and gravel must be sorted by size and

cleaned to remove dirt and clay95. The unit requires approximately 30 days for the

Schmutzdecke to mature and produce treated water. In the interim it is advisable that users not

drink this water as bacteria removal is limited. The sand within the filter should be kept wet at

all times to ensure the health of the biozone. To minimize the waste of water that runs through

the filter but cannot be consumed, it is advisable that the water be kept and recycled as the

filter improves or used for secondary water consumption needs (i.e. household cleaning,

watering of crops or sanitation purposes).

Distribution/Transportation

To minimize the ecological footprint and costs of making the filter the units should be

made locally or as close to this as possible. Ideally, moulds should be distributed by volunteers

to communities and units be made collectively. Communities should be approached by

37

educators early to explain and encourage the use of the filters. The filters will weigh

approximately 85kg96 excluding the sand used, have a volume of 53L, and stand 1m tall97. The

fine particles of sand should be added once the unit has been brought to the home to reduce

the load and sand shifting during transit.

Use

This filter is capable of producing 1L of treated water per minute with a fine sand height

of 20-25cm (see sample calculation in Appendix B). Fine sand has a hydraulic conductivity of

approximately 10-4m/s with a diameter of 125-250µm98. As the Schmutzdecke develops expect

the flow rate to drop to as low as 10L per hour99. While this is obviously a drastic drop, it may

still suffice for a family’s water needs. Do note that the slower the flow rate, the longer the

water remains in the biological layer and therefore the better the quality of water exiting the

system.

Maintenance

While backwashing improves the flow rate of sand filters it is not the most desirable

practice in water scarce regions. The process itself is very water intensive. It also requires a

pump and energy to drive the fluid up through the sand column and out in the opposite

direction. Furthermore, backwashing disturbs or entirely destroys the biological layer of

filtration that makes slow sand filtration so effective.

An alternative to backwashing is Wet Harrowing100. To do so, users plug the spout to

prevent water from draining out the unit. Water is added from the top into the filter and is

“slowly swirled around by hand”101. The individual cleaning the filter must avoid touching the

sand as this will disturb the biolayer. “The movement of water loosens the accumulated dirt,

which comes into suspension [and] this muddy water can then be carefully decanted, using a

cup”102. The process effectively dislodges particulate matter that has deposited itself deeper

38

within the first layers of sand while retaining the Schmutzdecke intact. “Often the filter is back

to normal operation within hours instead of days to weeks.”103

Removing the sand and washing should only occur every five to ten years104. In

situations where either backwashing or sand washing are employed as maintenance steps a two

column water filter is desirable. In such circumstances, two columns of equal capacity should be

set up (keep in mind size and weight constraints). One filter should be set up weeks earlier than

the other leaving it time to have the slime layer grow. Once this column is operational, the

second should be started up as well. The water that would normally run through the filter and

be disposed due to inadequate treatment can then be run through the fully functional filter and

consumed while the second column matures. Once both are running properly, they should be

used equally. Hence one will always need cleaning about a month or more sooner. This will

ensure that while the cleaned filter is redeveloping the biolayer the overall quality of water

consumed isl maintained.

Projects using biosand filters have found that “some filter owners clean their filter out

of routine, rather than because of blockage or inconveniently reduced flow rate”. Such

practices hinder the filter’s abilities and must be avoided105. Proper use through education is

imperative and should be followed up to ensure the success of such projects.

Flow rate reduction can also be associated with seasonal patterns. The rainy season

often produces more turbid water106. Such problems can be alleviated to some extent through

the employment of pre-filtration practices.

Filters can remain fully operational with no need for maintenance anywhere between 6

months and a year depending on water turbidity107. As such, scheduling cleaning on a calendar

basis is not the best practice. Rather, it should be performed only when flow rates are so low as

to hinder the objective of the system.

39

End of Life

The main components in the filter are the concrete column, the sand and the plastic

pipe. Concrete’s life expectancy can be between 30 to over 100 years given the environmental

conditions108. Since the concrete container will not be exposed to any degrading chemicals, is

resistant to normal weathering conditions and will not be moved often, it is safe to assume it

will last longer than 30 years. PVC pipe when used for drinking water will exceed 100 years of

service109. As mentioned above, sand will need to be thoroughly cleaned every 5-10 years.

Hence with basic maintenance practices these filters can last several generations within a home.

The concrete itself can be re-crushed and used as future ballast for other concrete projects. The

recycling of PVC is also possible although currently there are concerns about chlorine release in

industry practices110. Ultimately the end of life permits 100% recyclability.

40

Chapter 5 – Prototype In addition to the goal of selecting a recommended filtration technology, the

requirement of this project is to take said technology and build a test rig that will treat

simulated turbid, bacteria rich water, and run laboratory experiments to demonstrate its

effectiveness. To do so, it was necessary to first assess the requirements of the filter, around

which a design and testing procedure were outlined.

Functional Requirements

The basic requirements for the filter’s functionality were incorporated into the following

nine constraints on the design:

1) Most importantly the prototype must mimic the slow sand filtration process. An

appropriate head of water above the filter bed must be achieved to drive flow.

2) Dirty water must be added near the filter bed so as to minimize disturbance of the sand.

This will permit the growth of bacteria necessary for slow sand filtration’s success.

3) The filter must replicate conditions of daily use by a family unit. It should support use at

regular intervals. As both students involved are not able to monitor the filter daily, it is

necessary to create an independently operating system.

4) Since filter water stagnation for extended periods of time will ruin the bacterial growth

in the filter, the apparatus must provide a continuous cycle of water through it.

5) The testing rig should be designed from inert materials to ensure no contamination of

the effluent water.

6) There are two proposed methods of arranging a slow sand filter. The test rig (a single

system) should be designed to test both filter styles simultaneously. It should be

modular to permit easy incorporation of different designs of gravity-feed filters, should

the need arise to test them.

41

7) The system should handle different flow rates associated with each respective filter, as

well as be capable of handling the various fluctuations in flow rates over its lifetime –

generally, as filters age, their flow rates decrease.

8) The effectiveness of a slow sand filtration unit depends on the bacteria culture in the

filter bed hence appropriate germinating conditions must be met. The test rig must

operate under varying ambient temperature conditions, providing a consistently

controlled environment for the bacteria.

9) Lastly, the test rig is to be transportable, and therefore must be designed to fit into a

Honda CRV (the largest car available to the students). If the test rig cannot be designed

to fit in one piece, it must be designed for disassembly into components that will fit.

Design

An artistic rendition of the layout of the finalized design which supports the outlined

test rig requirements can be found in Fig 5.1. The design drawings themselves can be found in

Appendix D, the modeling of which was done using SolidWorks software.

Basic Operation

A ‘trough’ design was chosen as the most effective way of meeting several of the

functional requirements. Please reference Fig 5.1 for the following explanation. In this design,

water is drawn from the lower reservoir (at 1) and pushed up by a pump to the trough (at 2).

Connected to the trough are the overflow downspout (at 3) which carries excess water back to

the lower reservoir (at 1), and the filter columns (at 4) which draw water from the trough

through the filter bed (at 5) at their respective rates and back to the lower reservoir (at 6). The

turbid test water is added via the upper reservoir (at 7).

As aforementioned, the test rig requires a design that support two different methods of

arranging a slow sand filtration. It is suggested that the frequency of backwashing maintenance

42

can be reduced if the filter bed is arranged in the reverse manner111. In this case the gravel layer

is above the sand, as opposed to the conventional design of the sand layer on top. To comment

on the viability of such a filter, this second arrangement was also tested. In an effort to prevent

particles or filter sand escaping through the filter outlets and into the system, a simple piece of

tightly-woven fabric was placed over the opening, and held in place by the weight of the filter

bed.

Function

A water system height of 71.12cm (28”) above the filter beds was chosen, giving an

effective pressure head above the bed of 6.963kPa (see Appendix B for sample calculation). To

facilitate the addition of the highly turbid test water to the filter water column, the inlet holes

were placed several inches above the filter bed on the side of each column. This ensured that

the test water is added as close to the bed as possible, without disturbing the top layers of the

bed (functional requirements – FRs 1, 2).

The use of a pump to run the system ensured that the test rig does not need frequent

supervision. The test rig can be left running indefinitely, only requiring attention when adding

test water, or to top up water loss due to evaporation (FR 3). Additionally, the trough design

ensured that water is distributed to all filter arrangements on a continuous basis (FR 4).

The water in the trough is maintained at a constant height, hereafter referred to as the

‘system height’. Should one of the filter columns attached experience an increase in flow rate,

this will create a difference in column water height relative to the system height, and this

pressure difference will drive the flow from the trough into the column until equilibrium is re-

attained. If the flow rate slows, less water is pulled from the trough. Thus the trough design

allows for the varying flow rates of multiple filter arrangements (FRs 6, 7).

43

Using aquarium water heaters, the system temperature is maintained constant at 80oF.

These heaters were placed one per filter in each column in order to ensure that the surrounding

cold air did not interfere with the bacterial growth inside the filter (FR 8).

Lastly, in order to maintain a reasonable system height of water, the test rig was

required to be larger than the dimensions limiting its transportation. It was necessary to design

the rig for disassembly into appropriately-sized components (FR 9).

Materials

Because of cost constraints and available building tools, wood was used for the frame of

the structure. It was decided that the most suitable material for the filter columns would be 6”

diameter PVC piping because of its cost-effectiveness, durability, inertness, size, and since it is

used extensively in the construction industry, it is a very accessible form of piping to work with.

Transparent plastic PVC medical tubing and connectors were used for the majority of the tubing

(with clear plastic vinyl tubing used everywhere else). Lastly, to seal connections to the PVC

piping, a flexible, waterproof, silicone caulking was used. These materials were chosen to

conform with FR 5.

Methods

Contaminated Water Source

As previously discussed the populations of interest suffer largely from coliform

bacterial-related problems. In order to properly test a filter with respect to these specific issues,

an appropriate water source was necessary to find or create. Most local large freshwater

sources (including Lake Ontario) generally meet WHO standards, especially during the winter

season when a large quantity of the bacteria and algae die from the extreme weather

conditions112. Since the project spanned from autumn to early spring, it was necessary to find

44

some other consistent source of water, high in coliform bacteria. It was decided that the best

way to meet these requirements would be to culture a large, separate batch of contaminated

water. A 100 gallon aquarium tank was used to so facilitate approximately 30 gallons cultured

water. The bacterial content of the water was seeded using soil, an aquarium-grow solution

(rich in algae, phytoplankton, zooplankton, rotifers, krill, fish, yeast and other natural

ingredients), rotting potato peels, apple core, and peach pit, rusting iron nails, and a plant food

mix (containing 30% Nitrogen, 15% Phosphorous, 15% Potassium). The water was kept

stagnant, at a temperature of at 80oF, and underneath a 15W UV grow lamp. As water

evaporated it was replaced with tap water. To ensure that the chlorine present in the tap water

did not affect the bacteria population growing in the solution, water was left to stand for at least

24 hours before being added to the solution to allow the majority of chlorine to dissipate.

Testing Procedure

The following steps outline the processes undertaken to gather samples to test the

effectiveness of the both filtration arrangements:

(Please refer Fig 5.1 for the following instructions)

1) Stir up the contaminated water, and collect a 275mL sample.

2) Disconnect the filter columns from the trough (at 4).

3) Plug the outlets (at 6) to both filter columns (stagnate the flow in each filter).

4) Disconnect the tubing from the upper reservoir (at 7), and using these, drain the

columns of their water to a level a couple of inches from the top of the filter bed.

5) Reconnect the tubing to the upper reservoir, and add 6L of contaminated water to each

column.

6) Unplug the outlets on the filters and allow the contaminated water to drain through the

beds until the water levels reduce back to a couple of inches from the beds.

45

7) Add an additional 3L of contaminated water to each column, let 2L drain through, and

then take a 275mL test sample from each filter’s outlet. This step ensures that the filter

bed has been cleared of the system water before the sample is taken, so that the

sample results from contaminated water having run completely through the filter bed.

8) Reconnect the filter to the trough, and allow the system to replenish the water in the

filters.

Test Sample Analysis

Upon collection of the test samples, they were sent to Gelda Scientific & Industrial

Corporation for analysis. The bacterial-based tests run on the samples were: Heterotrophic

Plate Count (a measure of all of the bacterial load “that use organic nutrients for growth”113),

Total Coliform (bacteria that “belong in the family Enterobacteriaceae”, bacteria linked to

decay114), Escherichia Coliform (commonly known as “E. Coli”), and Yeast and Mould. These

particular tests were chosen to give an appreciable understanding of the bacterial content of the

samples.

46

Chapter 6 – Sample Analysis

Test Results

The following table is the collection of results taken by submitting two separate sample

sets one week apart to Gelda Labs for analysis. The aim of this thesis is to demonstrate that the

two columns of sand can bring bacteria values down to appropriate levels. The following table

contains the results obtained from testing:

Table 6.1 – Test Results

Sample Name Date of Submission HPC/ml Yeast/ml Mould/ml

TC-MF/ml

EC-MF/100ml

Flow rate L/day

Feed water Control 1 11/03/2009 6700 0 3 34 0

Feed water Control 2 18/03/2009 10000

40 0

Column A - Test 1 11/03/2009 14000 0 0 3200 0 2160

Column A - Test 2 18/03/2009 4800

2200 0 1926

Column B - Test 1 11/03/2009 40000 0 0 4100 0 969

Column B - Test 2 18/03/2009 6000

1500 0 22.5

Biosand Water Mix 18/03/2009 5400 0

System Water 18/03/2009 220 3

Discussion

Column A represents the standard sand column where sand is layered on top of gravel.

Column B is the reverse set up and sand is the final filter layer that water encounters within the

system. The two columns were set up to determine which achieves better quality, flow rates as

well as is better suited for maintenance.

Two sets of samples were collected and submitted to determine whether or not the

Schmutzdecke had enough time to fully develop. The first sample set was sent in three weeks

after the units were set up and first introduced to contaminated water. The second set was

submitted exactly one week afterward. The reader will notice that more samples were sent in

on the second date. While the first samples appeared improved upon visual inspection, the

results came back indicating otherwise. In both columns the results returned showed what

seemed as an inexplicable spike in the quantity of bacteria found in the treated water vs. that

47

found in the feed water. Determined to identify the point at which bacterial contamination

increased samples of the sand and the system water were also submitted in the second set. The

concern was that the live sand (normally used for artificial aquatic environments) mistakenly

purchased and used for the filter columns was breeding its own bacteria deeper into the

columns and contaminating the water supply. It was first realized that the sand was less than

ideal after approximately ten days of running the system with system water in a closed loop. To

correct for this, the column sand was removed and washed thoroughly, but proper disinfection

of the entire system was not possible. The sample submitted to determine how much bacteria

bred was sand left to sit with water for almost 24 hours. As can be seen, less than a day allowed

for the Biosand Water Mix to cultivate a heterotrophic count almost as large as that of the first

feed water sample.

System water was taken from the bucket that both columns flowed into when the

system was running on a closed loop. While results returned prove bacteria is present

elsewhere in the system, it along with the contaminated sand are not enough to explain the

discrepancies between expected and achieved results.

It is worth mentioning that both columns’ flow rates mysteriously increased a few days

before the first set of samples were collected to be submitted. Column A’s flow rate increased

by about tenfold sometime during the day, seven days preceding sample collection and Column

B achieved similar outcomes three days before. Speaking with Dr. James115 it was concluded

that channels had formed through the columns of sand over time and the water was flowing

through the path of least resistance—thus rendering the filters less effective.

However, this does not explain the increase in bacterial presence in both samples’

results. The underlying reason for this is attributed to particle suspension that must have

occurred while trying to collect the samples. To do so, the system water circulation was shut off

48

and allowed to drain out of the columns after which 6L of feedwater were fed through the

columns to collect 275ml samples. To prevent disturbance of the biolayer within the sand while

contaminated water was reintroduced, 2 inches of system water remained above the sand layer.

The column was then stopped as 3 L of feed water were added. At this point that the

momentum normally carrying the water down and through the columns rebounded against the

bottom of the filter loosening particles and bacteria found within the filter bed. This disturbed

bacteria (most of which was feeding off decaying matter carried deeper into the sand) was

flushed out when the water stopper was removed. Hence upon sample collection when another

3L were poured through (to reduce the effects of potential dilution of the first 3L with system

water) the bacteria found its way into the samples.

In support of this theory resettling of the fine sand did occur once the system was put

back into closed system mode. The flow rate of Column B slowed by an appreciable amount.

While originally operating at 969L/day, this dropped to 22.5L/day. Column B shows the effects

of particle suspension and resettling best because it is exposed to the most energy caused by

the pressure gradient. Hence the higher level of bacterial contamination. For this same reason,

it is also resettled more when flow was restored. Since a week passed before the second set of

data was collected this allowed the biotic activity to return to that more characteristic of

properly functioning sand filters. Thus there is a noticeable decrease in the amount of bacteria

carried through the system.

The system water value demonstrates that the filters function effectively to an extent.

Since contaminated water was added every 3-4 days (regardless of sample collection or not) if

the filters performed as poorly as suggested by the column sample data, the bacteria that

escaped would re-circulate and thrive within the system, and the effect would be compounded

by each instance of feed water addition. Instead, over several cycles, the system reduced the

49

bacterial content to 220ppm diluted in 65.65L. This same result would be achieved if 6L of feed

water carried through a filter returned a sample of 2407ppm, in other words a 77% decrease

from influent levels. This implies that for the pressure achieved, a deeper sand bed was

necessary to adequately treat the water.

Sources of Error

While the results are not entirely favourable, they do show that bacterial contamination

can be reduced if the filters are set up properly. As this project incorporated little course

material from previous classes but rather introduced new concepts that were incorporated in

the test, the errors in set up that are now apparent were not so during the design stage. These

sources of error are:

o contamination from tubes

o closed circuit problem (exposure of entire system to poorly treated water)

o Schmutzdecke development incomplete

o sand used had live bacteria culture

o filter bed not deep enough to eliminate all bacteria present

o disturbance in sand and Schmutzdecke created during sample collection

o heaters too warm

One major problem that was realized part way during the test phase was the possibility

that the closed system could effectively permit the entire filter unit to become infected by

bacteria that managed to escape the sand filter. As the Schmutzdecke takes time to mature, it

will not eliminate all pathogenic contamination upon first use. By creating a closed system that

kept the sand moist at all times and permitted the bio layer’s development it also gave bacteria

50

the ability to contaminate the exit tubing, bucket, pump and trough. This became apparent as a

slime layer developed on several surfaces of the unit beyond the filter columns.

Another problem briefly mentioned was the duration of time given for the

Schmutzdecke’s development prior to sample collection. The method used for gathering

samples will have disturbed this layer but not necessarily destroyed it and the one week period

may have permitted it to continue to grow despite having to first restore its previous state

before continuing.

The biggest factors of error were the inadequate sand depth to pressure (driving flow)

ratio and the lack of careful packing116. A sand depth of a few centimetres deeper would have

ensured that slower flow rates were met allowing the particulates suspended in water longer

contact time with the sand and biological layer to ensure contaminant removal. Likewise, better

packing of the sand would have prevented the channel burrowing that occurred. This, along

with a fine mesh placed over the sand to keep it in place would have prevented the particle

suspension effect that occurred during sample collection.

Finally the sand used for the filter, while fine enough, was covered in bacteria of its own.

Despite efforts to wash the sand once this was discovered, the column and rest of the system

were not properly disinfected, to eliminate any contamination present downstream.

While the heaters were installed out of necessity to ensure that the room’s low ambient

temperature did not drop the water’s temperature below life sustaining conditions, it may have

proved to be too warm for the correct balance of bacteria. Instead, weaker heaters or heaters

that could be adjusted to regulate water at a lower temperature should be used.

51

Chapter 7 – Recommended Future Actions If this thesis continued, the experiences thus far have led to the following suggestions

being implemented in the future.

1. Design shorter, smaller water columns with sand layers of varying relative height to find

the optimal height to flow rate condition. Flow rate equation should be used as a

precursor to estimating sand depth

2. Set up a column with only very fine particles of sand

3. Use silica sand that does not contain live bacterial culture

4. Do not heat the water in the columns

5. Take weekly samples of water filtered through the respective columns and monitor flow

rate

6. When setting up columns ensure sand particles are wet and packed well to minimize

potential air pockets that can later lead to channelling

7. Investigate the effectiveness of activated carbon used in conjunction with the sand filter

a. Test effectiveness of recycled carbon

b. Activate carbon personally to gage the complexity of the process and determine

feasibility in application to developing nations

52

Chapter 8 – Conclusion The aim of this thesis was to provide a filtration solution to address the water issues of

citizens in developing nations. To that end, countries were separated into four economic classes

using World Bank’s Atlas Formula. Of these, any nation falling within or below the Lower Middle

Income divide was targeted as a potential benefactor of private, household filtration. A list of

78 countries was used to provide a weighted average of the daily water needs of individuals

using information provided by Waterfootprint.org. As such, it was determined that the filter

selected must produce at least 86L of treated water per day per individual. Data provided by

UNEP’s GEMStat program aided in identifying which contaminants affected global populations

the most. While some heavy metals and trace ions turned out to affect select countries,

bacterial contamination plagued all water systems. Thus it was the goal of this project to

provide a solution that would reduce bacterial contaminant levels to Canadian Guidelines.

A detailed investigation of four filtration options was conducted (Granular Media Filter,

Barrier Media Filter, Disinfection Treatment, and Carbon Adsorption). The types of filters within

these classifications were thus ranked using a Pugh Matrix wherein Slow Sand filtration was

selected as the ideal option. A test rig designed for variations of this technique was developed

incorporating all parameters needed to ensure the successful treatment of contaminated water.

These included permitting growth of the Schmutzdecke to aid in the elimination of pathogens,

constant water flow, a flow rate greater than 86L/day, and transportability of the unit. The feed

water representing the tainted supply to be treated was made from decomposing food wastes,

dirt, iron nails, and seeded with aquarium feed and plant growth. A UV light and a heater were

also used to ensure that conditions necessary for optimal bacteria growth were achieved.

53

When samples were initially run through the columns, it appeared that bacteria was

added to the exiting water rather than being removed. A second set of samples sent in and this

showed that improper sample collection infected the samples sent in for testing. The method of

sample collection caused particulates within the sand to become suspend in the fluid

surrounding the sand particles thus exiting when the samples were taken. Contamination of the

system further downstream had less impact on the overall results achieved than previously

expected. Ultimately, the sand filters were capable of removing approximately 76% of

contaminants with flow rates of 969L/day. The addition of more sand would slow down the

flow and increase the feed water’s contact time with the Schmutzdecke thereby improving the

overall quality further.

A Life Cycle Analysis was conducted to determine the cost of the sand filtration unit. It

was based on an existent model described by BioSandFilter and found to be $5.59 if individual

moulds to make the concrete encasement were used 1000 times. While the results obtained

were not entirely representative of expected results, design improvements should correct the

problems encountered if this thesis is continued in the future and do indicate that sand filtration

is a cheap method of treating bacteria contaminated supplies.

54

Chapter 9 – Tables and Figures (Characterized by order of appearance in the document)

Table 2.1 – World Bank Class Division (imbedded in the document)

Table 2.2 – Target Countries

Africa

Algeria Angola Benin Burundi Burkina Faso

Cameroon Cape Verde

Central African Rep. Chad Côte d'Ivoire

Ethiopia Gambia, the

Ghana Kenya Liberia

Madagascar Malawi Mali Mauritania Morocco

Mozambique Namibia Nigeria Rwanda Senegal

Sierra Leone Somalia Sudan Swaziland Tanzania

Togo Tunisia Zambia Zimbabwe

Americas, the

Bolivia Colombia Dominican Republic, the Ecuador El Salvador

Guatemala Guyana Haiti Honduras Nicaragua

Paraguay Peru Venezuela

Asia

Afghanistan Armenia Azerbaijan Bangladesh Bhutan

Cambodia China Egypt Georgia India

Indonesia Iran Iraq Jordan Korea, DPR

Kyrgyzstan Laos Myanmar Nepal Pakistan

Philippines, the Sri Lanka Tajikistan Thailand Turkmenistan

Uzbekistan Yemen

Europe

Albania Moldova Ukraine, the

Oceania

Papua New Guinea

Table 2.3 – Major Global Contaminants (imbedded in the document)

55

Table 2.4 – Summary of WHO and National Water Contaminant Guidelines117 Geographic

Region WHO

(Guidelines) European Union

(Standards) Canada

(Guidelines) Australia

(Guidelines) New Zealand (Guidelines)

Japan (Standards)

United States (Standards)

Parameter mg/L mg/L mg/L mg/L mg/L mg/L mg/L

Algae, blue-green >1 toxic/10

mL

Aluminum 0.2 0.2 0.2 0.2 0.2 0.2

Ammonia- un-ionoized

* 0.5 0.5 0.5

Antimony 0.005 0.005 0.006 0.003 0.003 0.006

Arsenic 0.01 0.01 0.01 0.007 0.01 0.01 0

Barium 0.3 # 0.004 0.004

Boron 0.3 0.001 0.001 4 1.4 1

Bromate * 0.01 0.01 0.02 0.025 0.01 0

Cadmium 0.003 0.005 0.005 0.002 0.003 0.01 0.005

Calcium * 300

Chloride 250 250 250 250 200 250

Chromium 0.5 0.5 0.5 0.5 0.5 0.1

Coliform- total # 0/100mL 0/100mL 0 0

Colour # # & >5 degrees 15 colour units

Copper 2 2 2 1 2 1 1.3

Cyanide 0.07 0.05 0.05 0.08 0.08 0.01 0.2

Enterococci 0/250mL 0/250mL

Escherichia coli 0/250mL 0/250mL >1/100mL

Hardness * # & 300

Iron # 0.2 0.2 0.3 0.01 0.3 0.3

Lead 0.01 0.01 0.01 0.01 0.01 0

Lithium 0.9

Magnesium 300

Manganese 0.5 0.05 0.05 0.5 0.5 0.05 0.05

Mercury 0.001 0.001 0.001 0.001 0.002 0.0005

Mercury- inorganic

0.002

Molybdenum 0.07 # 0.05 0.07

Nickel 0.02 0.02 0.02 0.02 0.02

Nitrate 50 50 50 10

Nitrate + Nitrite 50 10

Nitrite 0.5 0.5 3 1

Odour & & &

pH * # 6.5-8.5 5.8-8.6 6.5-8.5

Selenium 0.01 0.01 0.01 0.01 0.01 0.01 0.05

Silver # # 0.1 0.02 0.1

Sodium 200 200 200 180 200

Solids- total dissolved (TDS)

* # 0.1 0.02 0.1

Sulfate 500 250 250 500 250

Tin * # 1 0.0005

Tritium 100Bq/L

Turbidity * # & >2 degrees n/a

Uranium * # 0.02 0.02 0.002

Vanadium 1.4 #

Zinc 3 # 3 1 5

Where: *,#,^,& represent no guideline, not mentioned, 250µS cm-1, and acceptable to consumers no abnormal change, respectively

56

Fig 2.1 – Iron Contamination in Asia

Fig 2.2 – Sulphate Contamination in Africa

57

Fig 2.3 – Population Representation for Africa

Table 3.1 – Anthracite Sizing (imbedded in document)

Fig 3.1 – Membrane Cross-Flow Filtration118

58

Fig 3.2 – Effective Removal of Pathogens for Membrane Technologies119

Table 3.2 – Membrane Energy and Pressure Demands120

Filter Type Pressure requirement

Energy demand

Microfiltration 100kPa 0.4kWh/m3

Ultrafiltration 525kPa 3 kWh/m3

Nanofiltration 875kPa 5.3 kWh/m3

Reverse Osmosis

1575kPa 10.2 kWh/m3

59

Table 3.3 – Ultraviolet Dosage Required121

Ultraviolet Dosage Required

For 99.9% Destruction of Various Organisms

(µW-s/cm2 at 254nm)

Bacteria

Mold Spores

Bacillus anthracis 8,700 Aspergillus flavus 99,000

B. Enteritidis 7,600 Aspergillus glaucus 88,000

B. Megatherium sp. (vegetative) 2,500 Aspergillus niger 330,000

B. Megatherium sp. (spores) 52,000 Mucor racemosus A 35,200

B. Paratyphosus 6,100 Mucor racemosus B 35,200

B. Subtilis (vegetative) 11,000 Oospora lactis 11,000

B. Subtilis (spores) 58,000 Penicillium digitatum 88,000

Clostridium tetani 22,000 Penicillium expansum 22,000

Corynebacterium diphtheria 6,500 Penicillium roqueforti 26,400

Eberthella typhosa 4,100 Rhizopus nigricans 220,000

Escherichia coli 7,000

Leptospira interrogans 6,000

Micrococcus candidus 12,300 Algae/Protozoa

Micrococcus sphaeroides 15,400 Chlorella vulgaris (algae) 22,000

Mycobacterium tuberculosis 10,000 Nematode Eggs 92,000

Neisseria catarrhalis 8,500 Paramecium 200,000

Phytomonas tumefaciens 8,500

Proteus vulgaris 6,600

Pseudomonas aeruginosa 10,500 Virus

Pseudomonas fluorescens 6,600 Bacteriophage (E. Coli) 6,600

Salmonella typhimarium 15,200 Hepatitis virus 8,000

Salmonella typhosa (Typhoid) 6,000 Influenza virus 6,600

Sarcina lutea 26,400 Polio virus 6,000

Serratia marcescens 6,200 Rotavirus 24,000

Shigella marcescens 6,200 Tobacco mosaic 440,000

Shigella dysenteriae (Dysentery) 4,200

Shigella paradysenteriae 3,400

Spirillum rubrum 6,160 Yeast

Staphylococcus albus 5,720 Baker's yeast 8,800

Staphylococcus aureus 6,600 Brewer's yeast 6,600

Streptococcus hemolyticus 5,500 Common yeast cake 13,200

Streptococcus lactis 8,800 Saccharomyces cerevisiae 13,200

Streptococcus viridians 3,800 Saccharomyces ellipsoideus 13,200

Vibrio Cholerae 6,500 Saccharomyces sp. 17,600

60

Table 3.4 – Activated Carbon Magnitudes and Applications (imbedded in document)

Table 3.5 – Water Contaminants that can be Reduced to Acceptable Standards by AC Filtration122

Primary Drinking Water Standards Contaminant

Maximum Contaminant Level, mg/L

Inorganic Contaminants

Organic Arsenic Complexes 0.05

Organic Chromium Complexes 0.05

Mercury (Hg + 2) Inorganic 0.05

Organic Mercury Complexes 0.002

Organic Contaminants

Benzene 0.005

Endrin 0.0002

Lindane 0.004

Methoxychlor 0.1

1,2-dichloroethane 0.005

1,1-dichloroethylene 0.007

1,1,1-trichloroethane 0.2

Total Trihalomethanes (TTHMs) 0.1

Toxaphene 0.005

Trichloroethylene 0.005

2,4-D 0.1

2,4,5-TP (Silvex) 0.01

Para-dichlorobenzene 0.075

Secondary Drinking Water Standards Contaminant

Secondary Maximum Contaminant Level, mg/L

Colour 15 colour units

Foaming Agents (MBAS) 0.5 mg/L

Odour 3 threshold odour numbers

61

Table 4.1 – Pugh Decision Matrix

Granular Media Filtering Barrier Media Filtering Disinfection Treatment

Sand Anthracite Membrane Ceramic Concrete Ultraviolet Radiation

Chemical Purification

Carbon Adsorption

Selection Criteria Weight Rating WS Rating WS Rating WS Rating WS Rating WS Rating WS Rating WS Rating WS

Parameters Flow Rate 4% 7 0.2763 7 0.2763 6 0.2368 3 0.1184 3 0.1184 8 0.3158 8 0.3158 4 0.1579

Size of Unit 1% 5 0.0329 5 0.0329 6 0.0395 6 0.0395 6 0.0395 8 0.0526 8 0.0526 6 0.0395

Capacity 1% 7 0.0461 7 0.0461 6 0.0395 6 0.0395 5 0.0329 8 0.0526 8 0.0526 6 0.0395

Life Availability of Materials 3% 8 0.2632 5 0.1645 2 0.0658 5 0.1645 5 0.1645 2 0.0658 4 0.1316 5 0.1645

Cost for manufacturing 7% 7 0.4605 5 0.3289 2 0.1316 7 0.4605 6 0.3947 1 0.0658 3 0.1974 5 0.3289

Cost for maintenance 3% 6 0.1974 5 0.1645 3 0.0987 8 0.2632 7 0.2303 1 0.0329 1 0.0329 4 0.1316

Maintenance requirements 4% 4 0.1579 4 0.1579 2 0.0789 7 0.2763 6 0.2368 2 0.0789 1 0.0395 4 0.1579

Ease of use 7% 6 0.3947 5 0.3289 3 0.1974 7 0.4605 7 0.4605 2 0.1316 1 0.0658 7 0.4605

Life expectancy 7% 7 0.4605 5 0.3289 3 0.1974 7 0.4605 7 0.4605 3 0.1974 1 0.0658 6 0.3947

Energy Needs 7% 8 0.5263 5 0.3289 2 0.1316 6 0.3947 5 0.3289 1 0.0658 3 0.1974 5 0.3289

Effectiveness Bacterial Removal 7% 7 0.4605 7 0.4605 7 0.4605 7 0.4605 6 0.3947 8 0.5263 8 0.5263 4 0.2632

Metals removal 4% 3 0.1184 3 0.1184 6 0.2368 4 0.1579 4 0.1579 1 0.0395 6 0.2368 4 0.1579

Major Ion removal 3% 3 0.0789 3 0.0789 6 0.1579 4 0.1053 4 0.1053 1 0.0263 6 0.1579 6 0.1579

Large particulates 3% 8 0.2105 8 0.2105 8 0.2105 8 0.2105 8 0.2105 1 0.0263 6 0.1579 6 0.1579

Clarity 4% 5 0.1974 5 0.1974 7 0.2763 6 0.2368 5 0.1974 1 0.0395 6 0.2368 7 0.2763

Taste 4% 4 0.1579 4 0.1579 7 0.2763 6 0.2368 5 0.1974 3 0.1184 6 0.2368 7 0.2763

Odour 4% 4 0.1579 4 0.1579 7 0.2763 6 0.2368 5 0.1974 3 0.1184 6 0.2368 7 0.2763

Health Risks During Production 1% 6 0.0789 5 0.0658 4 0.0526 7 0.0921 4 0.0526 3 0.0395 1 0.0132 6 0.0789

Storage of materials 1% 7 0.0921 6 0.0789 3 0.0395 7 0.0921 5 0.0658 3 0.0395 1 0.0132 7 0.0921

Use 7% 7 0.4605 7 0.4605 2 0.1316 8 0.5263 7 0.4605 5 0.3289 1 0.0658 7 0.4605

Disposal of waste 5% 7 0.3684 6 0.3158 4 0.2105 7 0.3684 7 0.3684 3 0.1579 1 0.0526 6 0.3158

Environment Use of Toxic Materials 4% 7 0.2763 6 0.2368 5 0.1974 7 0.2763 6 0.2368 3 0.1184 1 0.0395 7 0.2763

Reusability 5% 8 0.3684 5 0.2303 6 0.2763 7 0.3224 7 0.3224 1 0.0461 1 0.0461 3 0.1382

Recyclability 3% 8 0.2632 4 0.1316 3 0.0987 2 0.0658 2 0.0658 1 0.0329 1 0.0329 6 0.1974

Waste 4% 7 0.2763 5 0.1974 4 0.1579 6 0.2368 6 0.2368 1 0.0395 1 0.0395 6 0.2368

Weighted Average 100% 6.3816 5.2566 4.2763 6.3026 5.7368 2.7566 3.2434 5.5658

Rank 1 5 6 2 3 8 7 4

(where WS = Weighted Score)

62

Figure 5.1 – Prototype Layout (Artistic Rendition)

63

Table 6.1 – Test Results

Sample Name Date of Submission HPC/ml Yeast/ml Mould/ml

TC-MF/ml

EC-MF/100ml

Flow rate L/day

Feed water Control 1 11/03/2009 6700 0 3 34 0

Feed water Control 2 18/03/2009 10000

40 0

Column A - Test 1 11/03/2009 14000 0 0 3200 0 2160

Column A - Test 2 18/03/2009 4800

2200 0 1926

Column B - Test 1 11/03/2009 40000 0 0 4100 0 969

Column B - Test 2 18/03/2009 6000

1500 0 22.5

Biosand Water Mix 18/03/2009 5400 0

System Water 18/03/2009 220 3

64

Glossary Backwash—to clean out (a clogged filter) by reversing the flow of fluid123 Colloidal—in chemistry, the suspension of fine particles between 10 and 10,000 Å dispersed in a continuous medium, be it gas/liquid or solid, that prevents them from being filtered easily or settling rapidly124 Effluent—Fluid flowing out, treated water125 Feed water—water that first enters a filtration phase Floc—particles that have coagulated out of solution Gravitational Filter—Filter type that relies on gravity to push influent through media. Influent—Fluid flowing in126 Permeate—the filtered solution in a filtration phase Retentate—the portion of the feed solution that does not pass through a cross flow membrane filter Suspended solids—small solid particles distributed evenly in water as a colloid, used as one indicator of water quality. Turbidity—not clear or transparent because of stirred-up sediment or the like; clouded; opaque;127 Wet Harrowing—by means of disturbing water immersing layer of slime in filter, the ability to dislodge and hence removed particulate matter embedded

65

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72

Appendix A – GEMStat Analysis

Table A.1 – Full List of Contaminants

Major Ions

Metals Microbiology Nitrogen

Cyanide Aluminum Coliform Nitrate

Sodium Arsenic Faecal Coliform Bacteria

Nitrite

Sulphate Barium

Chloride Boron

Cadmium

Chromium

Copper

Iron

Lead

Manganese

Mercury

Nickel

Selenium

Zinc

73

Fig A.1 – Contamination Probability per Continent

74

Appendix B – Darcy’s Law Derivation and Application

Darcy’s Law:

Hydraulic Conductivity:

Specific Weight of Water:

Darcy’s Law Therefore Becomes:

This can then be applied, knowing the hydraulic conductivity, filter area, pressure, density of the

liquid, gravity and the filter depth to find for a flow rate through the porous media. Finer pores

have more resistance to flow, and so have lower values of hydraulic conductivity.

Calculation of Pressure Head

Water Pressure:

75

Appendix C – EIOLCA of Filter Parts Table C.1 – EIOLCA of Filter Parts

Energy Toxic Releases (Pre to Manufacturing Stage)

Parts

Cost (USD 1997) Total TJ

Non-Point Air (kg)

Point Air (kg)

Tot Air Releases (kg)

Water Releases (kg)

Land Releases (kg)

Underground Releases (kg)

Total Releases (kg)

POTW Transfers (kg)

Offsite Transfers (kg)

Total Rel/Trans (kg)

Plate 1113x950X2 $11.50 1.79E-04 8.24E-04 3.01E-03 3.84E-03 9.17E-03 1.55E-02 4.18E-04 2.90E-02 1.68E-03 1.16E-02 4.22E-02

Flat iron 50x11415x6 $2.31 3.60E-05 1.65E-04 6.05E-04 7.71E-04 1.84E-03 3.12E-03 8.38E-05 5.82E-03 3.37E-04 2.33E-03 8.47E-03

Flat iron 50x1415x6 $2.31 3.60E-05 1.65E-04 6.05E-04 7.71E-04 1.84E-03 3.12E-03 8.38E-05 5.82E-03 3.37E-04 2.33E-03 8.47E-03

Flat iron 50x938x6 $6.12 9.55E-05 4.38E-04 1.60E-03 2.05E-03 4.88E-03 8.27E-03 2.22E-04 1.54E-02 8.94E-04 6.18E-03 2.25E-02

M12x50 bolt & nut $0.52 4.38E-06 2.76E-05 8.90E-05 1.17E-04 4.62E-05 6.87E-04 1.92E-05 8.69E-04 3.93E-05 1.77E-04 1.09E-03

Plate 265x260x2 $0.75 1.17E-05 5.37E-05 1.96E-04 2.50E-04 5.97E-04 1.01E-03 2.72E-05 1.89E-03 1.09E-04 7.57E-04 2.75E-03

Plate 110x180x6 $0.65 1.01E-05 4.63E-05 1.69E-04 2.16E-04 5.15E-04 8.72E-04 2.35E-05 1.63E-03 9.44E-05 6.53E-04 2.37E-03

Flat iron 25x40x6 $0.03 5.09E-07 2.34E-06 8.55E-06 1.09E-05 2.60E-05 4.41E-05 1.18E-06 8.22E-05 4.77E-06 3.30E-05 1.20E-04

Flat iron 25x25x6 $0.04 6.36E-07 2.92E-06 1.07E-05 1.36E-05 3.25E-05 5.51E-05 1.48E-06 1.03E-04 5.96E-06 4.12E-05 1.50E-04

M12x75 bolt & nut $0.28 2.33E-06 1.47E-05 4.74E-05 6.21E-05 2.46E-05 3.66E-04 1.02E-05 4.63E-04 2.10E-05 9.46E-05 5.80E-04

Steel shaft 40x50 long $0.59 9.23E-06 4.24E-05 1.55E-04 1.98E-04 4.71E-04 7.99E-04 2.15E-05 1.49E-03 8.64E-05 5.97E-04 2.17E-03

Flat iron 50x50x6 $0.16 2.55E-06 1.17E-05 4.28E-05 5.45E-05 1.30E-04 2.20E-04 5.92E-06 4.11E-04 2.38E-05 1.65E-04 5.99E-04

Plate 942.5 (outer), 911 (inner)x252.5x2 $2.54 3.97E-05 1.82E-04 6.66E-04 8.49E-04 2.03E-03 3.43E-03 9.23E-05 6.41E-03 3.71E-04 2.57E-03 9.33E-03

Plate 848.2 (outer), 785.4(inner)x652.2x2 $5.80 9.04E-05 4.15E-04 1.52E-03 1.94E-03 4.62E-03 7.82E-03 2.10E-04 1.46E-02 8.46E-04 5.85E-03 2.13E-02

Plate 450x450x6 $0.07 1.03E-06 4.73E-06 1.73E-05 2.21E-05 5.27E-05 8.92E-05 2.40E-06 1.67E-04 9.65E-06 6.68E-05 2.43E-04

Plate 286x286x2 $0.89 1.39E-05 6.37E-05 2.33E-04 2.97E-04 7.09E-04 1.20E-03 3.23E-05 2.24E-03 1.30E-04 8.99E-04 3.27E-03

Plate 250x250x2 $0.68 1.06E-05 4.87E-05 1.78E-04 2.27E-04 5.42E-04 9.18E-04 2.47E-05 1.71E-03 9.93E-05 6.87E-04 2.50E-03

M25 nut $1.05 8.84E-06 5.57E-05 1.80E-04 2.35E-04 9.32E-05 1.39E-03 3.86E-05 1.75E-03 7.94E-05 3.58E-04 2.19E-03

Plate 80 diamx15 thick $0.41 6.40E-06 2.94E-05 1.07E-04 1.37E-04 3.27E-04 5.53E-04 1.49E-05 1.03E-03 5.99E-05 4.14E-04 1.50E-03

Square tube 50x50x3x330 $1.75 2.73E-05 1.26E-04 4.59E-04 5.85E-04 1.40E-03 2.37E-03 6.36E-05 4.42E-03 2.56E-04 1.77E-03 6.43E-03

Square tube 50x50x3x600 $1.59 2.49E-05 1.14E-04 4.18E-04 5.32E-04 1.27E-03 2.15E-03 5.78E-05 4.02E-03 2.33E-04 1.61E-03 5.85E-03

Angel iron 50x50x6x600 $5.97 9.31E-05 4.27E-04 1.56E-03 1.99E-03 4.76E-03 8.06E-03 2.17E-04 1.50E-02 8.71E-04 6.03E-03 2.19E-02

Steel shaft 16x360 $0.68 1.06E-05 4.88E-05 1.79E-04 2.28E-04 5.43E-04 9.20E-04 2.47E-05 1.72E-03 9.95E-05 6.88E-04 2.50E-03

Steel shaft 25x300 long $0.69 1.08E-05 4.96E-05 1.82E-04 2.32E-04 5.52E-04 9.36E-04 2.52E-05 1.75E-03 1.01E-04 7.00E-04 2.54E-03

Steel shaft 40x50 long $0.30 4.61E-06 2.12E-05 7.75E-05 9.88E-05 2.36E-04 3.99E-04 1.07E-05 7.45E-04 4.32E-05 2.99E-04 1.09E-03

Washer 60 diam $0.75 6.32E-06 3.98E-05 1.28E-04 1.68E-04 6.66E-05 9.90E-04 2.76E-05 1.25E-03 5.67E-05 2.56E-04 1.57E-03

Steel shaft 40x10 long $0.12 1.85E-06 8.47E-06 3.10E-05 3.95E-05 9.43E-05 1.60E-04 4.29E-06 2.98E-04 1.73E-05 1.19E-04 4.34E-04

Pipe 1" class 'B' 900 $2.15 3.35E-05 1.54E-04 5.62E-04 7.17E-04 1.71E-03 2.90E-03 7.79E-05 5.41E-03 3.13E-04 2.17E-03 7.88E-03

Steel shaft 18x150 long $0.18 2.80E-06 1.29E-05 4.71E-05 6.00E-05 1.43E-04 2.43E-04 6.52E-06 4.53E-04 2.62E-05 1.81E-04 6.59E-04

Bolts & nuts M10x25 $5.71 4.81E-05 3.03E-04 9.77E-04 1.28E-03 5.07E-04 7.54E-03 2.10E-04 9.54E-03 4.32E-04 1.95E-03 1.19E-02

Welding rods $6.61 3.31E-10 1.98E-08 0.00E+00 1.98E-08 0.00E+00 0.00E+00 0.00E+00 2.64E-08 0.00E+00 0.00E+00 2.64E-08

cement $2.03 5.28E-08 6.09E-09 0.00E+00 6.09E-09 0.00E+00 0.00E+00 0.00E+00 8.12E-09 0.00E+00 0.00E+00 8.12E-09

PVC elbow 1/2"* $0.98 1.44E-05 9.56E-05 2.75E-04 3.70E-04 5.51E-05 4.51E-04 1.73E-04 1.05E-03 1.73E-04 8.76E-05 1.31E-03

PVC pipe $1.16 1.71E-05 1.13E-04 3.26E-04 4.38E-04 6.52E-05 5.34E-04 2.05E-04 1.24E-03 2.05E-04 1.04E-04 1.55E-03

Total per 1000 parts $4.23 8.55E-07 4.11E-06 1.47E-05 1.88E-05 3.93E-05 7.71E-05 2.44E-06 1.38E-04 8.06E-06 5.18E-05 1.97E-04

76

Appendix D – Contribution to Final Document

Abstract Derek Humenny

Acknowledgements Dimitra Panagiotoglou

Method of Attribution Dimitra Panagiotoglou

Table of Contents Derek Humenny

List of Symbols Used Derek Humenny

List of Figures Derek Humenny

List of Tables Derek Humenny

Chapter 1 – Introduction

Motivation Dimitra Panagiotoglou

Objectives Dimitra Panagiotoglou

Chapter 2 – Water Consumption and Demand

Target Demographic Dimitra Panagiotoglou

Target Contaminants Dimitra Panagiotoglou

Data Analysis Dimitra Panagiotoglou

Division of GEMStat Data Dimitra Panagiotoglou

Data Trends Dimitra Panagiotoglou

Water Source Dimitra Panagiotoglou

Chapter 3 – Water Filtering Methods

Granular Media Filtering Derek Humenny

Sand Dimitra Panagiotoglou

Anthracite Dimitra Panagiotoglou

Barrier Media Filtering Derek Humenny

Membrane Technology Derek Humenny

Ceramic Dimitra Panagiotoglou

Concrete Dimitra Panagiotoglou

Disinfection Treatment Derek Humenny

Ultraviolet Radiation Dimitra Panagiotoglou

Chemical Purification Dimitra Panagiotoglou

Carbon Adsorption Derek Humenny

Chapter 4 – Technology Assessment

Method Selection Dimitra Panagiotoglou

Slow Sand Filtration Improvements Derek Humenny

Life Cycle Analysis Dimitra Panagiotoglou

Premanufacture Dimitra Panagiotoglou

Manufacture Dimitra Panagiotoglou

Distribution/Transportation Dimitra Panagiotoglou

Use Dimitra Panagiotoglou

Maintenance Dimitra Panagiotoglou

End of Life Dimitra Panagiotoglou

77

Chapter 5 – Prototype

Functional Requirements Derek Humenny

Design Derek Humenny

Basic Operation Derek Humenny

Function Derek Humenny

Materials Derek Humenny

Methods Derek Humenny

Contaminated Water Source Derek Humenny

Testing Procedure Derek Humenny

Test Sample Analysis Derek Humenny

Chapter 6 – Sample Analysis

Test Results Dimitra Panagiotoglou

Discussion Dimitra Panagiotoglou

Sources of Error Dimitra Panagiotoglou

Chapter 7 – Recommended Future Actions Dimitra Panagiotoglou

Chapter 8 – Conclusion Dimitra Panagiotoglou

Chapter 9 – Tables and Figures Derek Humenny

Glossary Dimitra Panagiotoglou

Works Cited

Appendix A – GEMStat Analysis Dimitra Panagiotoglou

Appendix B – Darcy’s Law Derivation and Application Derek Humenny

Appendix C – EIOLCA of Filter Parts Dimitra Panagiotoglou

Appendix E – Contribution to Final Document Derek Humenny

Appendix D – Detailed Prototype Drawings Derek Humenny

78

Appendix E – Detailed Prototype Drawings

79

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1. New York, NY: The McGrawhill Companies, Inc., 2003. 28 "Anthracite Coal." Science. 2008. ENasco. 9 Nov. 2008 <http://http://www.enasco.com/product/sb10656m>. 29 Ibid.,24 30 Ibid.,24 31 Allgeier, Steven, Brent Alspach, and James Vickers. Membrane Filtration Guidance Manual. Tech.No. 815-R-06-009. Office of

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32 Ibid.,31 33 Ibid.,31 34 Ibid.,31 35 Ibid.,31 36 Ibid.,13 37 Ibid.,13 38 Ibid.,31 39 Ibid.,27 40 Ibid.,13 41 "Membrane Technology." Lenntech Ultrafiltration. 2008. Lenntech Water Treatment & Air Purification Holding B.V. 10 Nov. 2008

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80

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Environmental Services Centre. Morgantown, WV: National Environmental Services Centre, 2000. 1-4. 59 Ibid.,58 60 Ibid.,27 61 Ibid.,27 62 Ibid.,27 63 Ibid.,27 64 Ibid.,27 65 Ibid.,27 66 Ibid.,27 67 Ibid.,27 68 Ibid.,27 69 Ibid.,27 70 Bungay, Henry R. "Adsorption." Chemical and Biological Engineering. 25 Feb. 2000. Rensselaer Polytechnic Institute. 13 Nov. 2008

<http://www.rpi.edu/dept/chem-eng/biotech-environ/adsorb/adsorb.htm>. 71 Knaebel, Kent S. Adsorbent Selection. Tech.No. Adsorption Research Inc. Dublin, OH. 6-9. 2008. Adsorption Reserarch Inc. 12 Nov.

2008 <http://www.adsorption.com/publications/adsorbentsel1b.pdf>. 72 Ibid.,13 73 Ibid.,13 74 Ibid.,71 75 Ibid.,71 76 Ibid.,71 77 Ibid.,71 78 Ibid.,71 79 Ibid.,71 80 "Activated Carbon From CPL Carbon Link." Activated Carbon. CPL Carbon Link. 10 Oct. 2008 <http://www.activated-

carbon.com/carbon.html>. 81 Ibid.,80 82 Ibid.,80 83 Ibid.,13 84 Ibid.,13 85 "BioSand Filter." Wikipedia, the free encyclopedia. 19 Mar. 2009 <http://en.wikipedia.org/wiki/BioSand_Filter>. 86 Ibid.,85 87 Ibid.,15 88 "Water purification." Wikipedia. Wikimedia Foundation Ltd. 20 Mar. 2009 <http://en.wikipedia.org/wiki/Water_purification>. 89 Ibid.,85 90 Ibid.,88 91 Carnegie Mellon University Green Design Institute. (2008) Economic Input-Output Life Cycle Assessment (EIO-LCA), US 1997

Industry Benchmark model [Internet], Available from:<http://www.eiolca.net> Accessed 1 January, 2008. 92 Mol, Adrian. Biosand Filter Casting Instructions. The Shieling, Wreay: BiosandFilter.Org, 2004. 93 Ibid.,92 94 Ibid.,92 95 Ibid.,92 96 Ibid.,92 97 Mol, Adrian, and Eric Fewster. Bio-Sand Filtration Mould Construction Guidelines. Wrexham: BioSandFilter.org, 2007. 98 "Particle size (grain size) -." Wikipedia, the free encyclopedia. 20 Mar. 2009 <http://en.wikipedia.org/wiki/Particle_size_(grain_size)>. 99Ibid.,13 100 Ibid.,13 101 Ibid.,13 102 Ibid.,13 103 Blackburn, Humphrey. ABCs of maintaining slow sand filters. Sept. 1998. EBSCO Industries, Inc. 19 Mar. 2009 <www.watertechonline.com>. 104 Ibid.,108

81

105 Ibid.,13 106 Ibid.,13 107 Ibid.,13 108 "Durability." Green Building, Energy Efficient Home and Buildings, Sustainable Architecture and Development with Concrete. Portland Cement Association. 20 Mar. 2009 <http://www.concretethinker.com/solutions/Durability.aspx>. 109 "Life expectancy of Rigid PVC pipe." PVC4Pipes. 18 Mar. 2009 <http://www.pvc4pipes.org/faq/life-expectancy-pvc-pipe.htm>. 110 "The PVC Debate." PVC and Vinyls by Solvin. 22 Mar. 2009 <http://www.solvinpvc.com/sustainabledevelopment/thepvcdebate/0,,5230-2-0,00.htm>. 111 Brouckaert, B.M., A. Amirtharajah, R. Rajagopaul, and P. Thompson. "Filter Backwash Option For Rural Treatment." Thesis. University of KwaZulu-Natal, Durban, 2006. 112 Boyd, MSc. Damien. "Water Quality." Telephone interview. 11 Mar. 2009. 113 "ScienceDirect - International Journal of Food Microbiology : Heterotrophic plate count bacteria—what is their significance in drinking water?*1." ScienceDirect - Home. 20 Mar. 2009 <http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T7K-4CCNC7B-3&_user=994540&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050024&_version=1&_urlVersion=0&_userid=994540&md5=39d855632c525b4f87e1e96a96c1f3eb>. 114 "Significance of total coliforms in drinking water - Total Coliforms - Guidelines for Canadian Drinking Water Quality: Guideline Technical Document." Welcome to the Health Canada Web site | Bienvenue au site Web de Sant. Health Canada. 19 Mar. 2009 <http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/coliforms-coliformes/significance-importance-eng.php>. 115 James, BSc, MS, PhD, MA, PEng. David F. "Sand Column Understanding." Personal interview. 19 Mar. 2009. 116 Ibid.,115 117 "Chemical Summary Tables." Water Sanitation and Health (WSH). 2008. World Health Organization. 10 Oct. 2008 118 Cross-flow Filtration. "Filtration." Wikipedia. 25 Feb. 2002. Wikimedia Foundation. 17 Oct. 2008

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