Water Purification
2008In
Cambodia
Water
WaterPurification
Purification In
In Cambodia
Cambodia
2008 Engineers Without Borders Challenge
Team B – Tutorial 7
Patrick Donovan
Jessica Equid
Beau Mavric
Tom Pope
Andrew Stead
John Verran
Water Purification In Cambodia 2008
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Water Purification In Cambodia 2008
Executive Summary
Engineers Without Borders (EWB) presented our team with the task of devising a solution to
Cambodia’s water problems, and in particular those of the Kandal province. In order to
develop a complete solution in this area, we narrowed the objective of this task to designing
a water filter capable of treating water at the collection point of an arsenic contaminated
bore well. The device was to be specifically designed for use in the Kandal province in
Cambodia, where issues relating to the cleanliness of water are prevalent. Through intensive
research, design and thorough testing, our team completed the set task and fulfilled our
objective.
The final design consisted of a dual chamber model with each cavity focusing on one stage
of the filtration process. When water is introduced to our design, through an input pipe in
the roof of the filter, it is first passed through 70kg of rusting iron nails. This stage serves to
remove arsenic via zero-valent iron adsorption. Following this the water is directed under
the separation between the two cavities and flows upwards through a layer of porous
concrete that supports a 400mm tall column of sand and ash. This phase functions as
turbidity and pathogen removal, as well as being effective at nullifying the iron taste present
in the water after the first stage. After passing through both filtration stages, the water can
be extracted from the filter via a tap located 50mm from the top of the sand. The two
filtration mechanisms are housed in a brick structure with concrete slabs serving as the base
and roof of the design.
A great deal of research, brainstorming and testing was undertaken in order to reach our
final design. Initial research was focused on developing a viable solution for removing
harmful pathogens from contaminated water. Technologies to remove turbidity, pathogens
and arsenic were investigated with consideration given to their cost, sustainability,
effectiveness and complexity. These technologies included pasteurisation, distillation,
porous concrete filtration, reverse osmosis, chemical sterilisation, sand filtration and zerovalent iron adsorption. By way of meticulous research and testing, we chose to include sand
filtration and zero-valent iron adsorption as the filtration technologies to be used in our final
design.
Sand and ash filtration is known to remove pathogens and turbidity from contaminated
water. As sand and ash are readily available as part of the landscape in Cambodia, sand
filtration seems to be a technique that is economically viable in a developing nation. Zerovalent iron adsorption is the method used in our filter that will be responsible for removing
arsenic from water. As this technique simply functions by passing water over rusted nails,
the only cost associated is the initial purchase of the nails. Hence, the system for water
filtration that we have designed is an efficient, simple and cost effective procedure for
filtering contaminated water.
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Water Purification In Cambodia 2008
The recyclability and sustainability issues associated with our model were a key focus point
for our group throughout the design process. In the event of deconstruction of the
structure, we considered it important that all materials and waste products could be either
reused or disposed of in an environmentally friendly manner. We selected many of our
building materials such that they complied with this objective.
It is important to consider ongoing maintenance of such a project as a lack of regular
maintenance could lead to the filter functioning in an undesirable manner. In order to
simplify and minimise maintenance required, we devised a simple and infrequent
maintenance routine that can be carried out by locals. This provides for an easy-to-use and
sustainable solution to the water filtration problem in Cambodia
The implementation of an education programme will play an integral role in the success of
this project. Our team has identified different groups of people who require education in
relevant areas in order for our design to be successful. Education programs will be assisted
by the use of illustrated manuals to accommodate all persons in the village.
Our team decided that implementing a village scale filtration system would be the only way
of meeting World Health Organisation standards for drinking water, while keeping the
solution economically viable. Due to the fact that the Cambodian government is not
currently supporting projects such as this, we were compelled to investigate other avenues
for funding. Such organisations include RDIC and UNICEF, in particular, UNICEF’s Millennium
Development Goal.
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Water Purification In Cambodia 2008
Team Reflection
We entered this challenge as an unconnected group of first year engineering students.
Although few of us knew each other before this project commenced, we grew into the team
that we are today. Over the semester, we have learned invaluable lessons about teamwork,
design processes, communication and sustainable development.
The humanitarian context and national competition surrounding this design project were
our primary motivating factors. From the beginning, our task was never thought of as a
simple assignment or university assessment. It was our goal to deliver a real system that
would improve the lives of real people. While our initial efforts focussed largely on the
technical aspects of design, we soon realised that, in order to achieve our goal, it was
necessary to consider the implementation and lifetime of our water filter. Throughout this
process we developed an understanding of the need for a sustainable and culturally
appropriate solution.
Effective communication was essential to our design process. Within the first two weeks we
set up an internet ‘wiki’ which served as a central hub for sharing and discussing our
research. As the project progressed, this website evolved into a forum for collaborating on
the design and documentation for the project. Group discussions took place regularly via
internet telephony and weekly face-to-face meetings. Initially, not all of these discussions
were productive, prompting us to focus on more efficient organisation and time
management.
During the research phase, topics were assigned to different team members who shared
their information and insights with the group. Preliminary designs were developed as a
group, after which a schedule for prototyping, testing and report writing was drawn up. As
the deadline drew nearer, these schedules became more comprehensive as individual tasks
were listed and assigned to team members, to be completed by a set due date.
Weekend sessions for prototype construction and testing also served as bonding
experiences for the team. This team cohesion caused us to work harder and more
productively in the weeks leading up to the project’s conclusion.
This project has been both rewarding and enlightening. The experience, skills and
camaraderie we have gained through our involvement will continue to serve us throughout
our lives as professional engineers.
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Water Purification In Cambodia 2008
Our team would like to thank Engineer’s Without Borders and the University of Western
Australia for giving us the opportunity to take part in this challenge.
Patrick Donovan
Jessica Equid
Beau Mavric
Andrew Stead
Tom Pope
John Verran
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Water Purification In Cambodia 2008
Contents
1 Introduction and Problem Statement
1.1 Objectives
pg 11
pg 11
1.2 Design Requirements
pg 11
1.3 Ethics
pg 13
2 Background
pg 14
2.1 Water Usage and Supply
pg 14
2.2 Water Quality Data
pg 15
2.3 Societal Scenario
pg 16
2.3.1 Cultural Values
pg 16
2.3.2 Current Systems
pg 17
2.3.3 Overseas Programs
pg 17
2.4 Economic Scenario
3 Water Treatment Technologies
3.1 Technologies Investigated
pg 18
pg 20
pg 20
3.1.1 Chemical Sterilisation
pg 20
3.1.2 Pasteurisation
pg 21
3.1.3 Distillation
pg 21
3.1.4 Reverse Osmosis
pg 22
3.1.5 Porous Concrete Filtration
pg 23
3.1.6 Sand Filtration
pg 24
3.1.7 Zero Valent Iron Adsorption
pg 26
3.2 Design Selection
pg 27
3.2.1 Design Selection Details
pg 27
3.2.2 Design Performance
pg 29
4 Design Solution
pg 30
4.1 Structure
pg 32
4.2 Sand Filtration Stage
pg 35
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Water Purification In Cambodia 2008
4.3 Nail Filtration Stage
pg 37
4.4 Construction
pg 39
4.5 Materials Costing
pg 41
4.6 Maintenance
pg 42
5 Design Testing
pg 43
5.1 Arsenic Removal
pg 44
5.2 Nails Rusting
pg 46
5.3 Porous Concrete Tests
pg 46
5.4 Flow Rate Tests
pg 47
5.5 Turbidity Removal
pg 48
6 Implementation
pg 49
6.1 Capital
pg 50
6.1.1 Human Capital
pg 50
6.1.2 Physical Capital
pg 51
6.2 Education
pg 52
6.3 Installation
pg 55
6.4 Monitoring and Maintenance
pg 58
6.5 Waste Management
pg 58
6.6 Project Costing
pg 60
6.7 Funding
pg 63
7 Impact Assessment
pg 64
7.1 Economic Impact
pg 64
7.2 Environmental Impact
pg 65
7.3 Social Impact
pg 66
8 Conclusion
pg 68
9 Reference List
pg 70
10 Acknowledgements
pg 473
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Water Purification In Cambodia 2008
11 Appendices
pg 74
11.1 Concrete Tests
pg 74
11.2 Nail Rusting Tests
pg 78
11.3 Investigation of Sludge
pg 81
11.4 Flow Rate Investigation
pg 83
11.5 Prototype Construction
pg 85
11.6 Arsenic Testing
pg 87
11.7 User Manual
pg 93
11.8 Maintenance Manual
pg 94
11.9 Construction Manual
pg 98
11.10 Distillation Experiment + Costing
pg 111
11.11 Reasons for Arsenic Contamination
pg 113
11.12 Water Borne Diseases
pg 115
11.13 Arsenic Health Effects
pg 116
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Water Purification In Cambodia 2008
1 Introduction and Problem Statement
On a daily basis, thousands of Cambodians are denied access to clean water. The state of
the Cambodian water supply is such that 80% of deaths in Cambodia are as a result of water
borne illness (RDIC, 2008). Although a small proportion of the Cambodian population
currently filter their water via a porous ceramic filter, 15% of filter users still contract
diarrhoeic infirmities from their drinking water. In addition to this, sixteen percent of
Cambodian’s source their water from deep wells where arsenic levels are high (UNICEF,
2007). While deaths from chronic arsenic poisoning are not yet dramatically high in the
nation, the toll is expected to rise as long term effects such as cancer of the skin, lungs,
urinary bladder, and kidney begin to manifest. Villagers from the Kandal province utilise a
number of water sources, each with different health concerns. During the dry season, when
other water sources are scarce, more villagers turn to contaminated groundwater as their
source of water. While there have been a number of efforts focussed on the removal of
bacteriological contaminants from surface and rain water, little has been done to address
the arsenic contamination issues associated with groundwater.
1.1 Objectives
It was our objective to design an effective water filter using alternative materials or
processes for Cambodians that will help nullify the health problems brought about by
unsafe water in Cambodia. The filter should be capable of treating water from an arsenic
contaminated bore well at its collection point. While the 2008 Engineer's Without Borders
Challenge focussed chiefly on the Kandal Province of Cambodia, we set ourselves the
additional goal of developing a solution that is applicable to a wide range of locales.
1.2 Design Requirements
The success of a design of a water filter for Cambodia is centred on a number of key
requirements. The design needs to comply with national standards with regard to pathogen
and arsenic removal as well as have the capacity to be easily integrated in to the current
Cambodian lifestyle. Furthermore, the proposed filter should be designed such that the
parts are low-cost and locals will be capable of the building and maintaining the filter.
The World Health Organisation (WHO) demands a certain level of efficiency in pathogen
removal in order to deem water emitted by a filter to be safe. The international standard for
drinking water is that there must not be any microorganisms. Furthermore, the Cambodian
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Water Purification In Cambodia 2008
standard for arsenic in water is set at < 50 parts per billion (ppb), which equates to 50µg of
arsenic per litre of water. Water from deep wells in Cambodia has an average arsenic
concentration of 176 ppb, so a filter would have to be roughly 70% efficient at removing the
substance from solution in order to reduce arsenic concentrations to below local standards.
Additionally, the success of a water filter in Cambodia dependant on the seamless
integration into the lives of the users. The people of Cambodia have a number of cultural
requirements with regard to their drinking water. These must be considered in order to
have some confidence in the successful introduction of a water filtration system to their
community. Two of these requirements are that drinking water must have a low level of
turbidity - it is very important to Cambodian people that their water at least appears to be
clean (RDIC 2008) and that passing water through a filter must not significantly alter its
taste. Due to lack of education surrounding hygiene and water quality in rural townships, a
water filter will not be successful, regardless of its efficiency, if it necessitates major changes
in the beliefs and lifestyle of Cambodia’s people.
Another requirement of a successful filtration system for Cambodia is that it is able to be
constructed using local materials and labour on site. In order for the filter to be a plausible
solution to water cleanliness problems, it is important that the structure itself be simple to
construct and easy to maintain. Ideally, low-skill construction workers should be competent
in the building phase and maintenance should be kept to a minimum as delegating jobs
could prove to be difficult due to the lack of structure in many Cambodian communities. In
particular, any maintenance should be low intensity, low risk and low cost. In order to
minimise upkeep, the filter should be designed to have a life-span of over 5 years.
Moreover, the cost of the filter per user will have a phenomenal impact on the extent to
which it proves useful. Although many people die in Cambodia as a result of water-borne
illnesses, studies show that residents are still hesitant to spend money on water filtration
solutions due to their extreme poverty (UNICEF, 2007). In order to combat this, it has been
discussed that instead of designing a filter to match the average Cambodian’s budget, the
filter should be designed to fall in the price bracket that is likely to be acceptable to an
independent organisation.
The requirements that a filter must meet in order to stand a chance of being successfully
implemented in Cambodia are clear. In order to solve the problem of water filtration in
Cambodia, one must address filtration efficiency, respecting local customs and funding the
proposed solution.
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Water Purification In Cambodia 2008
1.3 Ethics
As engineers in training it is of utmost importance to understand and adhere to the ethical
requirements of a professional engineer. Throughout the project, we have attempted to act
both in an ethical and responsible manner. Ethical codes were at the forefront of our
selection making and design process during which we considered what was in our client’s
and the community’s interest. We considered it our duty to conduct thorough and accurate
testing of the filter’s performance and to honestly assess the filter’s impact on the
surrounding community.
As future engineers, upholding the values of Engineers Australia and regulate was seen as
critical. This report makes it apparent ethical concerns have guided us throughout the
design process.
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Water Purification In Cambodia 2008
2 Background
2.1 Water Usage and Supply
Cambodian villagers obtain their water from a wide range of sources, particularly in rural
areas. Due to Cambodia’s monsoonal climate, with biannual rainfall peaks in June and
September/October, seasonal flooding is prevalent. At these times, surface water is a
common source for household water. A study conducted by The United Nations Children's
Fund (UNICEF) and the Water and Sanitation Program in 2007 indicated that in the dry
season (February to April), 48% of respondents use surface water as their primary water
source, 16% of people use deep wells greater than 10m in depth, 30% use shallow wells, 8%
use stored rainwater and 2% use bottled water (UNICEF, 2007). The study also revealed that
all households stored their water in containers, 32% of which were uncovered and the
majority were also outside. Furthermore, 43% of Cambodian people used their hands as a
means of retrieving the water from the containers, resulting in additional contamination
(UNICEF, 2007).
Cambodian Villager's Water Sources
surface water
deep wells
shallow wells
stored rainwater
bottled water
2%
8%
46%
29%
15%
Rural Development International Cambodia (RDIC) has found that on average, one
Cambodian will use 35L of water per day (RDIC, 2008). Of this amount, 2-3L is used for
drinking and the remaining amount is for cleaning, livestock, dish washing and other
household activities (RDIC, 2008). As the average household contains 5 people (UNICEF,
2007), household usage per day is about 175L per day.
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2.2 Water Quality Data
The two major water quality concerns within the Kandal Province are water borne diseases
and the natural occurrence of arsenic. Water borne diseases are defined as bacteria, viruses
and other parasites contracted by consumption of water. This includes diarrhoea and the
particularly lethal and infectious gastroenteritis Cholera. Water borne diseases are most
commonly contracted by the faecal to oral path. Escherichia coli or E. Coli is a common
bacteria found abundantly in the lower intestines of warm blooded mammals and normally
indicates water contact with faeces. As a result the mostly harmless bacteria is a common
indicator used widely used as a quantitative measurement for bacterial contamination of a
water source and its presence normally indicates additional biological activity. More
detailed investigation of water borne diseases relevant to the Kandal Province can be found
in appendix 11.13.
Arsenic contamination occurs equally in two natural forms, arsenites (As(III)) and arsenates
(As(V)). The most prevalent species in deep bore water are inorganic arsenic. Inorganic
arsenic is arsenic compounds bonded with elements other than hydrogen and carbon.
Arsenic causes the onset of the chronic and cancerous diseases arsenicosis. The WHO
guideline for arsenic is less than 10ppb (parts per billion) with the Cambodian health
standard being 50ppb. Further investigation of arsenic’s health effects can be found in
appendix 11.14 and geographical explanation for high occurrence within the Kandal
Province can be found in appendix 11.12.
Extensive field testing has being undertaken by the World Health Organisation (WHO), RDIC
and UNICEF to quantify the extent of the problem. Results from WHO showed one-third of
94 unique samples exceeded WHO’s Guidelines Values for health concern and 46% exceed
Cambodia’s recently introduced Drinking Water Quality Standards (WHO - 2007).
A RDI study in 2004 of two large population villages showed 80% of samples testing positive
for E. Coli bacteria, a major indicator of faecal contamination. Lake water was 100% positive
for both coliform and E. Coli. These numbers were expected because the villagers use of the
lake for washing and bathing themselves and their animals introducing contamination (RDIC
– 2004). The preconception that well water would remain uncontaminated was proven to
be false (RDIC - 2005). Shallow well water was 10% positive for coliforms and 76% tested
positive for E. Coli (RDIC -2005).
Tests by the WHO targeting the Kien Svay and Takhmau districts of Kandal Province
detected alarmingly high levels of arsenic in primary tests warranted secondary testing. 70%
of secondary samples exceeded WHO acceptable level of 10µg/L or 10 parts per billion
(WHO – 2007). Concentrations exceed 504 µg/L and averaged over 130 µg/L. Detailed
explanation of the factors contributing to the high levels of arsenic present in the Kandal
Province can be found in appendix 11.12.
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Water Purification In Cambodia 2008
2.3 Social Scenario
2.3.1 Cultural Values
Multiple field studies have been conducted to uncover the cultural values and behaviours
of Cambodians in regards to water consumption. The results of these studies were used
during our design process to in order to implement a culturally acceptable solution. We also
have discovered that many Cambodian's lack a basic water drinking practises to improve
health standards.
Observations in arsenic affected areas showed that most people preferred rain water over
deep well water (Feldman et al. 2006). This is supported by the statistic that 48% of
Cambodians use surface water as their primary water source and 8% used stored rain water
from previous seasons (UNICEF, 2007). This is a result of other minerals like iron and
manganese that are commonly found in arsenic infected water that affects the aesthetics
and palette of the water. Many villagers understand the dangers of iron in their drinking
water as its taste and odour is noticeable (Frey et al. 2006). Also villagers can associate
diarreahoa with certain water sources and iron poising as their symptoms occur quite
rapidly (Frey et al. 2006).
Arsenic is odourless, tasteless and the onset of arsenicosis often takes over a decade so
there is an understandable ignorance with regard to arsenic contaminated water. RDIC
concluded that villagers know about health issues but do not act on them. There is also a
widely accepted belief that if water is clear then it is safe (RDIC, 2008).
Residents in the Kandal Province reported that the main reason some deep wells were not
in use was because the aesthetic properties of the water had been unacceptable to the
community, in particular high levels of iron and hardness (Feldman et al. 2006). However,
attitudes towards taste are believed to evolve with the continued consumption of water
from this source. Feldman concludes “...aesthetic properties of water is often ignored or
underestimated by agencies involved in rural water supply projects, which tend to focus
exclusively on improving the microbiological quality of water...” (Feldman et al. 2006).
Therefore our design must not only satisfy the technical requirements but also comply to
values Cambodian's hold.
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2.3.2 Current Systems
At present, the two main water purification methods used in Cambodia are pasteurisation
and ceramic filtration. 53% of households heat water to remove biological in their
household (UNICEF 2007). An estimated 200 000 people or 1.5% of the population currently
employ some form of filtration at home (UNICEF, 2007).
Important lessons can be learnt from the Potters for Peace ceramic clay filter Filtron, which
has already sold over 50,000 in Cambodia alone (RDIC, 2008). The filter is a fired clay pot
with a gravity fed flow rate of around 3L per hour. With an expected life of 44 months, they
produce 99.9999% E. Coli free water (Brown, 2007) at a cost of around US$10. A field study
of 509 households conducted by the Water and Sanitation Program (WSP) showed that less
than 48% of filters remained in operational use 24 months after implementation and only
31% of households used it daily (UNICEF, 2007). Only 6% of households purchased
replacement filter elements in the Kandal Province, demonstrating the lack of acceptance of
the CWP’s (UNICEF 2007).
2.3.3 Overseas Programs
Water contamination is present throughout the world. The problems we are tackling are
evidently not isolated to Cambodia as approximately 1.4 million children worldwide die
from diarrhoea each year (WHO, 2008). Many solutions have already been devised and
implemented to improve drinking water quality. By critically analysing the relative success
these designs and taking advice from experts in the field, we can increase the chances of our
design being successfully implemented. Overarching all of this is our ethical responsibility to
act in the interests of the community, thus consideration of Cambodia’s values and
behaviours is paramount to the success of our design.
Investigating other water purification systems with particular focus on similarities and in
particular, the impact that these similarities have on social acceptance, will enhance the
final social acceptability of our design. Many systems have failed due to complex production
methods, high maintenance, high costs, insufficient flow rate, and/or reliance on materials
unavailable in remote villages (Shrestha et al. 2004). In addition, current systems target
individual issues resulting in ineffective filters or systems too complex to use.
A particular iron adsorption filter was the 3-Kolshi, a relatively cheap, homemade, gravity
fed, three-pitcher filter unit. The average flow rate of 1-5 litres per hour was insufficient and
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Water Purification In Cambodia 2008
users commonly skipped filtration if they did not have time (Ngai et al. 2004). Also without
meticulous maintenance the filter clogs down to 1 litre per hour.
A similar filter, the 2-Kolshi, targeted arsenic removal by mixing a chemical cocktail of
sodium hypochloride, ferric chloride and ash to the water before a one stage sand filtration
process. The logistical process of distributing the chemicals was a challenge. These
chemicals were not available locally and had to be shipped from Nepal. Also, the filter
required users to add the chemicals and wait 30 minutes, which like the 3-Kolshi, was not
time efficient and was disregarded by many users.
Arsenic Removal Plants set up in India provided a significant lesson about the importance of
the aesthetics of water. There were reports of the output being red and yellow in colour as
well as having a bad odour. This was most likely due to the iron based arsenic removal
process employed. Even though the final product is harmless in comparison to the
contaminated input, the water was not accepted among local Indian’s (Hossain, 2005).
2.4 Economic Scenario
In the past decade the Cambodian economy has strengthened significantly, with high
amounts of growth in the garment and tourism industry. In the period of 2001-2004
Cambodia grew at a rate of 6.5% growth in GDP. In 2008, the GDP is currently at
$26.19billion, mainly composed of the agriculture sector and the services sector (CIA 2008).
Despite the recent economic activity, many Cambodian’s are still facing poverty.
CWP’s have being deemed as too expensive for rural Cambodian’s despite the US$10 cost
for a filter with a design life of 44 months. RDI state “The truly poor cannot afford to pay for
any technology we provided without assistance” (RDIC, 2006). This informed feedback lead
to consideration of a community scale filter.
However a community scale water filter in most scenarios will be classed as a public good. A
public good is a good that cannot exclude users. This non-exclusive quality prevents the use
of a user-pays system. As a result initial funds for construction will need to be sourced
externally preferably an aid agency supporting work in the region or large scale drinking
water projects. It appears that a communal size filter will be the economically preferred
scale of our design.
The Cambodian economy will encounter various positive effects due to the construction of a
community scale water filter. As this construction is based at the location of the bore wells,
local tradespeople will be required to be used in the erection of the filter. Hence, this will
increase domestic expenditure and create more work for the local companies. As we are
relying on external aid agencies to fund our project, this will provide an autonomous
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Water Purification In Cambodia 2008
injection of investment into the economy, which will eventuate in the investment amount
being ‘multiplied’, due to the effects of the multiplier). Albeit, the impact of the multiplier
will decrease over time, the impact will still be prevalent.
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Water Purification In Cambodia 2008
3.0 Water Treatment Technologies
During the initial phases of the project, several water treatment technologies were
investigated to determine their suitability for inclusion in our design. These included
methods to remove turbidity, pathogens and arsenic from drinking water. For each
technology, consideration was given to the cost, sustainability, effectiveness and
complexity. A more thorough examination was conducted on technologies that appeared
feasible for our final design.
3.1 Technologies Investigated
3.1.1 Chemical Sterilisation
Chemical additives to water are used throughout the developed and the developing world
as a method for sterilisation. The most plausible solutions to Cambodian water supply is the
use of chlorine, Halazone tablets or Iodine. The active ingredient in Halazone tablets is a
chlorine compound. These chemicals are not locally or regionally produced and would have
to be imported.
The elements chlorine and iodine have been used successfully for centuries as disinfectants.
When enzymes from pathogens come into contact with these halogens, a hydrogen atom is
exchanged with the halogen causing the enzyme to change properties. When an enzyme
does not function properly the bacterium or cell dies.
The Kandal Province does not have a centralised water distribution system and chemically
treating a natural water supply like a lake or aquifer could have disastrous environmental
consequences. Hence, treatment would most likely be carried out on a household scale.
Parallels can be drawn to PSI’s PUR system operating in Uganda where households obtain
individual chemical sachets and treat water themselves. While the E. coli 0157 H7 bacterium
is killed within 1 minute of contact time with these halogens, longer times for Hepatitis A
(>16 minutes) are required to guarantee purification of these fecal pollutants (Lenntech
2008). Other sources suggest for reasonable disinfection a one hour contact time (Backer
1995).
Issues arise with the palette of the water, however addition of small amounts of vitamin C
can render the water nearly tasteless (Lenntech 2008). Purification effectiveness carries a
strong positive linear correlation with contact time and dosage quantities.
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Water Purification In Cambodia 2008
3.1.2 Pasteurisation
Pasteurisation is the process of heating liquids with the intention of eliminating
microbiological organisms. All bacteria (including V. Cholera and E. Coli) is rapidly killed at
60o C and all viruses (Hepatitis A) are destroyed instantly at 65o C (Burch and Thomas 1998).
55% of households in Cambodia reported boiling their water before drinking (UNICEF 2007)
and a majority of households have a wood powered stove for cooking, so implementation of
a pasteuriser would be relatively seamless.
While pasteurisation is highly effective at neutralising pathogens, it has no effect on
nonliving contaminants including arsenic, manganese, turbidity and hardness. This
necessitates further purification stages to bring contaminated water within national health
standards.
The main issue with the technology is the inefficient utilisation of energy and the high
energy cost of the process. Furthermore, the energy in rural Cambodia will most likely be
sourced from the unsustainable practice of burning of trees. However with respect to the
experimental data also presented in the following section, over 0.5kg of wood would need
to be burnt to provide the minimal amount of drinking water for a family for one day. The
environmental impact of large scale implementation deems it an unsustainable practise.
However, the time and energy requirements of pasteurisation of water make the practice
unsustainable. To raise the temperature of 2 litre of water from 20 degrees to 70degrees
Celsius require 418 Kilojoules of energy. In practice, the low efficiency of energy transfer of
a combustion stove and the tendency of users to heat the water until boiling point means
that the energy used is many times higher. With biological mass such as wood being the
main source of fuel in household stoves, the carbon footprint and destruction of flora due to
the wide-spread use of pasteurisation constitutes an unsustainable burden on the natural
environment.
3.1.3 Distillation
Distillation is the process of boiling water and collecting the steam, then condensing the
steam to create a pure water source. Distillation can be undertaken on many scales,
however due to high initial capital outlay and associated fuel costs, a household scale would
be more viable. A simple kettle with a metal condensing tube, running the water into a
collection container can be used in conjunction with a fire place as a basic distiller.
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Water Purification In Cambodia 2008
Distillation encapsulates the process of pasteurisation but improves effectiveness by
removing all other non living contaminants. As the temperatures experienced in distillation
are more extreme and exist for a longer time, pathogenic sterilisation can be guaranteed.
Problems with effectiveness arise with operating temperatures and the crude form of
distillation implemented. With no precise form of temperature control, maintaining the
sample water at a constant 100oC is highly unlikely. This may result in contaminants of a
higher boiling point boiling off and as a result passing contaminates to the ‘purified’ water
source. Also vapour pressure of the solution being purified has to be considered in
reference to actual boiling point of solvents. However, in simple distillation the difference in
vapour pressures negates Raoult's law to create a rule of thumb that simple distillation is
only effective in separating materials where their boiling point differs by more than 25oC.
Due to the large specific and latent heat of water, large amounts of energy are required to
boil the water for drinking. The most likely source of this energy on a large scale would be
burning of the rubber tree.
Experiments were carried out to determine the practical energy expenditure in distillation
as outlined in appendix 11.11. These experiments concluded that the burning of
approximately 13.53kg of wood is required to provide enough drinking water for an average
household of 5.9 people. This is excluding fuel for other usages of the stove and the energy
consumed in reaching operational temperature. These figures are undesirable with respect
to the environmental impact in a country where traditional fuels like wood, charcoal and
other biomasses account for 85% of the national energy supply balance (World Bank 1995).
Another environmental impact includes the disposal of concentrated waste left in the pot
after the distillation process.
3.1.4 Reverse Osmosis
Reverse Osmosis fundamentally relies on the naturally occurring physical process of
diffusion. This process directs water through semi-permeable membranes with pores
minute enough to filter out all viruses, bacteria and dissolved particles. The dense polymer
membrane allows solvents to pass through while preventing the migration of solutes.
Natural osmosis occurs when low concentration fluids move through the membrane to
fluids with high concentration of dissolved solvents (Binnie et al. 2002). A large pressure in
the vicinity of 250psi applied to the side of high concentration will overcome or reverse the
naturally occurring osmosis process to encourage migration of water from high to low
concentration, hence creating a pure water supply. Reverse Osmosis is 98-99% efficient at
removing monovalent ions at 200psi.
22
Water Purification In Cambodia 2008
The process is one that involves high operating costs as well as large amounts of waste
water (Henrichs et al. 2007). Large energy inputs are required to achieve and continually
apply the pressure. As a result reverse osmosis appears to be an economically unviable
solution for water filtration in Cambodia.
3.1.5 Porous concrete filtration
Porous concrete is typically made from a mixture of coarse aggregate, fine aggregate, sand,
cement, and water and has the capacity to effectively filter harmful pathogens in water. The
materials involved in the construction of porous concrete are readily available and
affordable in rural locations in Cambodia, hence making porous concrete a worthwhile
filtration technique to investigate.
The combination of coarse and fine aggregate ensures that water is able to flow through the
concrete, yet the pores remaining small enough to guarantee efficient filtration. A study
conducted in relation to a Korean dam system found that in order for the flow rate of water
through the concrete to be productive, the amount of void space needs to be greater than
14% (I-Song, C et al. 2002), with values of 15-25% being typically used for porous concrete
pavements (Majersky, G 2008).
In order to consider porous concrete as a viable solution for water filtration, the individual
pore sizes must be less 0.1mm in diameter (Taghizadeh, M.M et al. 2007). The size of
harmful bacteria usually falls in the range of 0.2-8µm while porous concrete has only been
proven to filter bacteria that are greater than 2µm. However, a study conducted in Iran
discovered that porous concrete encourages the growth of biological masses; ‘helpful’
bacteria that demonstrate 90-100% efficient coliform removal (Taghizadeh, M.M et al.
2007). To ensure the biological mass remains in the filter, the flow rate of water through the
filter cannot be too great and care needs to be taken when backwashing the filter. Porous
concrete has also been shown to be effective in removing iron and aluminium from water to
a level within the standard for safe drinking water set by the Environmental Protection
Agency (Majersky,G 2008). The other major contaminant in Cambodian water supplies is
arsenic, and porous concrete is ineffectual in removing this toxin due to the microscopic
nature of arsenic ions.
23
Water Purification In Cambodia 2008
3.1.6 Sand filtration
Slow sand filtration has been successfully used commercially since 1829. It has being
claimed that “Under suitable circumstances, slow sand filtration may be not only the
cheapest and simplest but also the most efficient method of water treatment” (Huisman –
1974).
Water Flow
Concentrated Biological
Growth or Schmutzdecke
Sand/Ash Medium
Left: A simple sand filter
San filters are capable of removing physical and biological contaminants from water.
Unexpectedly, the filters are capable of filtering particles that are significantly smaller that
their own void pore sizes. The physical filtering properties of the sand medium provide for
superb turbidity and aesthetic quality control of the final water product.
While bacterial flow can be restricted by the physical characteristics of the filter, the
biological processes in a slow sand filter contributes a significant amount to the purification
ability. Due to the low hydraulic loading on the sand, most of the solid particles are found in
the top 5 to 20 mm of the filter (Biosand 2004). A gelatinous or biofilm layer is established in
the top few millimetres of sand and is known as Schmutzdecke. The Schmutzdecke is a sticky
film consisting of decomposing organic matter, iron, manganese and silica which acts as a
fine filter to remove colloidal particles in water.
Initially in the Schmutzdecke, and as time goes on the rest of the filter, algae and a range of
aquatic organisms grow. As water passes through the Schmutzdecke, foreign material is
trapped and is metabolised by the bacteria, fungi and protozoa present. Bacteria such as
Pseudomonas and Trichoderma have been shown to have demonstrated as effective
24
Water Purification In Cambodia 2008
bacterial control agents in hydroponic environments (Oasis, 1991). The sand in this process
provides the supporting medium for the biological growth.
Research conducted on constant flow sand filters shows the majority of biological processes
occur in the top 0.4m of sand (ASCE, 1991). Similar numbers are expressed in further
research where biochemical reactions such as converting organic materials into amino acids
only take place in the top layer of sand (Huisman and Wood, 1974) and being supported by
observations that oxidation of nitrogenous organic compounds of depths more than 0.4m
are incomplete (Muhammad et al. 1996). The health of the bacterial layer is dependent on
remaining wet at all times and this was due to the water containing sufficient levels of
oxygen. The growth of these bacteria can become rampant and will over time restrict the
flow rate of the sand filter. Additionally the biofilm requires 2-3 weeks to ‘ripen’ and exhibit
maximum purification ability (Palmateer et al. 1999).
Above: Electron microgrpah showing the formation of a biological layer on a sand filter
The sand used in these filters is the standard granular sediment found around the world.
Fine grade of between 0.15 and 0.35 mm is recommended but most importantly the grain
size should be kept consistent throughout the filter, or the sand will settle in layers of
density and reduce porosity (Schulz and Okun, 1984).
Ash can be added to the sand mixtures to improve turbidity and aesthetic qualities (Newnan
et al. 2004). Ash, soda ash or sodium carbonate is found the ash of burnt plants. The sodium
carbonate reacts with calcium hydroxide hardeners to form a precipitate that is filtered by
the sand. Also in technical briefs comparing the effectiveness of the twelve dominant water
purification technologies, only charcoal filters and distillation received the maximum
effectiveness indicator for removing odour and taste (Shaw et al. 1999).
25
Water Purification In Cambodia 2008
Water produced from slow sand filters is of exceptionally good quality with 90-99% bacterial
reduction (Vigneswaran 1995). Research carried out in several developing countries by
(Kaiser et al. 2002) showed an average of 93% of faecal coliform removal. The (Shaw et al
1999) rated sand filtration a superior bacterial and viral removal indicator than that of
ceramic filters (4 compared to 3, 4 being maximum effectiveness on discrete scale 0-4). Field
research in Nepal showed that 10 in 12 properly functioning sand filters totally removed all
E. Coli (Lee 2001) and similar research by Global Outreach Student's Association showed
average coliform removal rates of 99.6% in 25 filters constructed (GOSA, 2001). Similar
research in Brazil from 55 filters reported average removal rate of 99.7% for faecal coliform
and 98.6% for E. Coli (Liang, 1998).
Over time the filter will become clogged or ‘fouled’ and require maintenance. The solid
sediments collecting in the sand restrict flow rate. However the primary concern affecting
flow rate is the build up of the Schmutzdecke that restricts the flow rate in a similar
mannerism. Typical maintenance usually involves periodically removing the top 10mm of
sand to remove the densest biological mass. It should be noted that the water quality does
not deteriorate but rather improves with the build up of biological mass, but flow rates
become unacceptably low. Effective backwashing systems have shown to significantly increase
time between maintenance (Newnan, 2001).
3.1.7 Zero valent iron adsorption
Dissolved arsenic can be removed from water by adsorption onto a ferric hydroxide surface.
Arsenites (As(III)) are oxidised to form arsenates (As(V)) and a reaction between As(V) and
Fe(III) species forms an insoluble precipitate on the surface of the ferric hydroxide (Mohan &
Pittman, 2007). Numerous arsenic removal systems utilise ferric hydroxide adsorption to
reduce arsenic concentrations in drinking water to safe levels. While some filters
incorporate specially manufactured ferric hydroxide adsorbents, the manufacture of these
adsorbents is relatively expensive and complex.
Above: Adsorption of dissolved Arsenic onto an iron nail
26
Water Purification In Cambodia 2008
An alternative approach is the generation of ferric hydroxide in situ, through the corrosion
of elemental (zero valent) iron. Ferric hydroxide is a natural component of rust which is
readily formed on iron surfaces exposed to sufficient water and oxygen. Several low cost
filters have been able to efficiently remove arsenic by running water through iron nails or
filings. Zero valent iron also favourably contributes to arsenic removal through several other
reactions that take place (Mohan and Pittman 2007).
The efficiency of arsenic removal for such a system is dependent on the surface area of the
ferric hydroxide and the amount of contact time between the water and ferric hydroxide
surfaces. The production of rust is essential to this process and can be increased by ensuring
the surfaces are exposed to sufficient air and water. The contact time between water and
the ferric hydroxide can also be increased by constricting the flow rate through the
adsorbent (or during adsorption). High pH and phosphate levels can impede the adsorption
of arsenic but are generally not present in deep bore water (Meng et al 2002).
During the corrosion of iron, not all of the rust produced adheres to the iron surface, with
dislodged rust creating turbidity and sediment in the filter. This turbidity gives output water
a red-brown colour and an unpalatable taste. For this reason, filters using zero-valent iron
adsorbents generally require a second stage capable of removing fine rust particles
suspended in the water.
The rusting and adsorption process effectively consumes the iron, meaning that unlike
adsorbents such as activated alumina, iron is non-regenerable. While this has a negative
impact on sustainability, the low cost, high availability, long lifetime and low toxicity of
waste products make zero-valent iron systems feasible for long-term use. For example, the
Kanchan filter, which uses iron nails as the adsorbent, reportedly lasts for 4+ years, with 5kg
of nails treating 15-20 litres of water per hour. According to the Kanchan filter’s
construction manual, annual cleaning of the nails and sand-filter portions may be necessary
to maintain sufficient flow and arsenic removal.
3.2 Design selection
3.2.1 Design Selection
Early design considerations of distillation initially provided many attractions. Our research
into the success of Filtrón revealed that the per user cost of the system is essential in design
selection. A low unit cost of US$2.86 per unit for a distillation filter was appealing compared
to the Filtrón. Distillation also has a design life of over 10 years, minimal maintenance
requiring no monetary costs and most importantly it removes arsenic. The appeal of the
easily being scaled up to community size provided great versatility.
27
Water Purification In Cambodia 2008
Our experiments into the energy usage of distillation found the process to be
unsustainable. The large energies required make the process not economically viable and
the large use of fuels to supply this energy has a negative environmental impact.
The arsenic removal capabilities of the filter were always intended to be the ‘selling’ point
and as a result it became the centre point of our design selection from there on in.
Removing arsenic ions from water provides a more difficult purification situation than the
larger and living water borne diseases. The technique of distillation has already been
dismissed and reverse osmosis required too much financial start up and ongoing costs.
While iron based absorption of arsenic is an inexact procedure with effectiveness based on
probability; the cost, maintenance, simplicity and sustainability of the technology provided
the incentive to work around the design flaws. The implications are that we require
approximately 70kg of pure iron to achieve our desired flow rate and our high performance
expectations.
The impressions on health that water borne diseases create in the developing world is the
reason our second primary design objective was to remove these parasites from drinking
water. We considered porous concrete for a considerable time, research finding that it is
extremely effective in removing water borne diseases. In addition it provides a very high
flow rate at minimal cost and construction intricacy. However, when we attempted to
construct samples (appendix 11.1) we uncovered that construction methods to create
concrete with such purification properties were vague. Our construction of eight samples
inspired from a range of research papers provided apprehensive conclusions. Again our
ethical responsibility as engineers in training upholding tenant three of Australia Engineers
Code of Ethics, we could not present a design with such ambiguity of a critical component.
A sand/ash filter relying on an active hypogeal layer supported structurally by porous
concrete provided a superior solution and outstanding purification performance. The porous
concrete provides a filter for turbidity and larger particles, while the remaining impurities
are filtered further by the sand. Arranging the filters in this order extends the time between
clogging, and in conjunction with backwashing capabilities can operate for extended periods
of time without maintenance.
Through critical analysis of technologies, awareness of the wider scenario and adhering to
overarching moral guidelines we confidently present two viable technologies, that when
utilised together can produce a safe drinking water source.
28
Water Purification In Cambodia 2008
3.2.2 Design Performance
The design selection process can be summarised in the table below. Each technology was
given a rating out of 5 for each of the six key selection criteria. Five 'water drops' indicate
the most desirable outcome in each category, one drop being the least desirable.
Waste
Product
Implicati
on
Technology
Environmental
Impact
Unit
Cost
Ongoing
Costs
User
Friendliness
Effectiveness
Rating
( /30)
Chemical
Sterilisation
18
Pasteurisation
15
Distillation
15
Reverse
Osmosis
13
Porous
Concrete
23
Slow-Sand
Filter
29
Iron
Absorption
22
29
Water Purification In Cambodia 2008
4.0 Design Solution
7
Our final design is a two stage water filter with the capacity to remove arsenic, turbidity and
pathogenic contaminants. The unit is capable of removing up to 90% of arsenic. The unit is
designed to be attached directly to an arsenic contaminated bore well, providing villagers
with a clean, safe and reliable source of potable water.
The materials selected have been chosen to be cheap, locally available and environmentally
sustainable. Filters can be constructed on site by tradespersons and can be maintained by
villagers with minimal training. With proper maintenance, the projected lifetime of the
system is in excess of five years, although, long-term testing is required to verify this figure.
Input Connection
Rusted Nails
Loose Aggregate
Half PVP Pipe to
Restrict Flow Rate
Backwash Tap
Water is pumped into the filter via the bore-well’s hand pump, entering the filter via an inlet
in the top of the right hand tank. The water then passes through the nail bed, where arsenic
is absorbed by contact with iron oxide. To allow sufficient time for arsenic removal, the flow
rate through this stage is constricted as water is forced to pass through small holes in the
PVC half-pipe. Water leaving the arsenic removal stage then passes through a gravel bed as
it travels down to the bottom of the right hand tank.
30
Water Purification In Cambodia 2008
Output Tap (not to
scale)
Imbedded Porous
Concrete
Sand/Ash Stage
Narrow Channels
Water passes through large holes at the bottom of the partition separating the left and
right hand tanks. Larger particles collect as sediment in the gravel and along the bottom of
the filter. Water then passes upwards through the porous concrete slab as it enters the sand
filter stage, where turbidity, bacteria and viruses are removed. Clean water is obtained by
opening the tap on the right hand tank.
Water flow is dictated by the pressure differences between each chamber. Water
accumulated in the input chamber diffuses through the various purification elements as the
water levels between the two tanks equalise. This causes the water level of the output
chamber to rise above the level of the tap, which can then be opened to release the purified
water.
Above: Changing water levels as water is pumped through the filter
31
Water Purification In Cambodia 2008
4.1 Structure
The filter stands 1245mm tall, is 1140mm wide and 1590mm long. The base of the unit
consists of a 75mm thick concrete slab. The walls of the structure are made from bricks and
mortar, with a 10mm layer of mortar on all internal walls. The top of the unit consists of two
concrete slabs, one covering each chamber as shown below. The separation of slabs
provides for easy access to the arsenic phase chamber to conduct essential maintenance.
Removable Concrete Lid
32
Water Purification In Cambodia 2008
33
Water Purification In Cambodia 2008
A large porous concrete slab is constructed into the brick structure directly below the sand
filter, with the edges sealed with cement to prevent leakage through the sides of the slab.
The internal central wall extends the full height of the structure, with gaps left between the
bottom bricks to create channels for water to flow between the two sides.
Porous Concrete
External Rendering
Gaps in Bricks
Concrete Base
PVC fittings and taps pass through gaps in the brick structure and are set in concrete to
create a water tight seal. A PVC pipe with removable end-cap is incorporated into the base
of the right hand tank to allow the filter to be drained and backwashed.
The filter has been designed to be permanently connected to the bore to maximise
simplicity and filter use. A PVC pipe is supported on either ends by its respective connection
joint. PVC pipe provides a non-corrosive, flexible and easy to assemble system comparative
to its leading alternative, galvanised steel.
Cement, bricks and mortar were chosen because they are cheap, environmentally friendly
and locally available. Brick and mortar walls were chosen over concrete walls primarily due
to their simplicity in construction, construction time and precision required in the
construction process. Bricks long term availability is more dependable than alternative
materials and they are therefore a more sustainable option.
The external structure provides a durable, water tight housing for the internal components
of the filter. The sturdy structure can remain robust throughout the design life of 5 years in
which it is exposed to varying environmental and operational conditions. Its low-profile
minimises visual impact and the disturbance to the community around it.
Right: One of the prototype filters constructed during
design testing
34
Water Purification In Cambodia 2008
4.2 Sand Filtration Stage
The sand filter stage has been designed to remove turbidity and pathogens from water.
Sand Ash Medium
Concentrated Region
Of Biological Mass
Porous Concrete
The choice of sand is a critical factor of the design and must have a uniform grain size to
prevent the formation of density layers and the consequential reduction in porosity. As a
result sand can be locally and freely sourced as long as granularity is a uniform value
between 0.15 and 0.35 mm (Schulz and Okun - 1984). However, extensive sifting and
washing must take place before it can be effectively used in the filter as outlined in the
construction manual (appendix 11.10).
s
Physical filtration also occurs throughout the sand filter. Despite the relatively large size of
sand particles used, it is capable of filtering physical masses of sizes greater than 0.01mm
and constricting bacteria with sizes as small as 1µm (WEDC - 1999). These filtering
capabilities contribute for the turbidity removal in the filter.
35
Water Purification In Cambodia 2008
Over time the filter will fill with solid mass and reduce porosity. The majority of solid mass
collects in the bottom 5 to 20 mm of the sand layer, where most of the biological mass
grows (Biosand – 2004). To prevent this fouling reducing the flow rate of the filter, a
backwashing mechanism is implemented to maintain flow rate throughout out the design
life.
The sand consists of a uniform mixture of 80% sand and 20% ash by volume. The addition of
ash to the sand mixtures improves turbidity removal and reduces hardness. Sodium
carbonate is found in ash of burnt plants and reacts with calcium hydroxide to reduce
hardness. The readily available ash of burnt tress is an appropriate selection for our filter as
it can be easily located in Cambodian villages (Newnan et al – 2004).
While the biological mass or Schmutzdecke is concentrated in the bottom 20mm of our
filter, research conducted on continually flowing sand filters shows the majority of biological
processes occur in the top 400mm of sand (ASCE - 1991). To optimise the size of our filter a
vertical height of 400mm was chosen. Theoretical calculations for flow rate rely on too
many uncontrollable variables and as a result are unreliable. Consequently, the dimensions
of the filter have been chosen based on published research from other filters.
36
Water Purification In Cambodia 2008
Slow sand filtration systems like Oasis Design’s, with a compressed sand chamber 800mm
tall, have been shown to have a practical flow rate of 0.2m/hour. Flow rates can be
increased up to 0.4 m/hour (Huisman et al – 1974) and continually operated sand filters
showed no significant reduction in faecal coliform reductions with flow rates of 0.1, 0.2 and
0.3m/hour (NEERI - 1982).
Given our chosen height of 400mm, a conservative estimate of the flow rate of our sand
filter is 0.25m / hour.
4.3 Nail filtration stage
Above: Rusted iron nails
The stage of our filter is the arsenic removal stage, which removes dissolved arsenic via
adsorption onto the surface of a bed of rusted iron nails. Rust formed on plain steel nails
generates ferric hydroxide, which reacts with inorganic arsenic to form an insoluble
precipitate. As discussed in section 3.1.7, the efficiency of arsenic removal is dependent on
the amount contact between water and the ferric hydroxide on the nail’s surface. In our
design, contact is improved by increasing the quantity of ferric hydroxide and the length of
time the water is in contact with these surfaces.
The quantity of ferric hydroxide is increased by ensuring that the iron nails are exposed to
sufficient water and oxygen. Experimental evidence collected by our group revealed that the
suspending nails on or above the water level generated the most rust. A more complete
description of these tests is provided in sections 5.1 and 11.2 of this report.
The quantity of ferric hydroxide is also increased by choosing nails with a larger surface
area. Assuming that a nail can be modelled by a cylinder with radius r constant height h, the
surface area of a fixed mass of nails is inversely proportional to the radius of the nails. In our
design, nails with a diameter of 1.5-3 mm have been chosen to provide a sufficient surface
area.
37
Water Purification In Cambodia 2008
Above: Graph showing the relationship between surface area and the nail radius
In addition to maximising the amount of ferric- hydroxide surface in the arsenic stage,
increased contact is also achieved by limiting the flow rate water through the nails bed.
With the flow rate being set at 200L per hour, the final consideration for the design of the
arsenic removal stage is the mass of nails.
Theoretical information relating nail mass and rates of arsenic removal are not well
documented. While figures have been published concerning the performance MIT’s
Kanchan filter, we considered it unethical to base the design of this life-critical system on a
single information source. Quantitative data on the arsenic removal rates of nails were was
obtained by laboratory investigations conducted by group as summarised in the table
below. A more complete description of these test can be found in Appendix 11.5.
Nail Mass
Flow Rate
Arsenic Removal
Kilograms of nails per
litre of water
Required nail mass
for 200L / Hour
38
Kanchan Filter
5 Kg
15-20 L per hour
90-95%
0.33 – 0.5 Kg
Team B Lab tests
12 Kg
60 L per hour
~90%
0.2 Kg
50 - 66 Kg
40 Kg
Water Purification In Cambodia 2008
These figures suggest that a nail mass of ~50Kg should be sufficient to remove 90% of
inorganic arsenic from contaminated water. In practice, heavy usage and the presence
minerals such as iron in bore water may lead to lower arsenic removal efficiency. Hence, we
have chosen to incorporate 70Kg of nails in our design, to increase longevity and
accommodate variations in mineral content.
4.4 Construction
The process of constructing our filter is a relatively simple procedure. The filter is to be
constructed on-site by two labourers, with at least one capable in bricklaying and in making
concrete. The labourers will be provided with a Construction Manual and a set of technical
drawings (See Appendix 11.10) outlining the construction process and dimensions of the
filter. The two documents will have to be used in conjunction with each other to produce a
satisfactory water filter. After sufficient experience in the building process, labourers can be
utilised as trainers.
The construction process has been broken down into four main sections, each containing
numerous steps. Before the process can begin, the workers must locate and collect all the
materials and equipment required for the building process. The Construction Manual
contains a checklist for each section of the process outlining what materials and pieces of
equipment will be necessary.
The first section concerns the creation of the concrete slabs required for the base and roof
of the design. Once all of the materials required have been sourced, construction can begin.
Initially the labourers must mix the cement and sand in a wheelbarrow or bucket. A ratio of
1 cement : 4 sand is to be used. Water should be added and the mixture stirred until the
desired texture is achieved. This is an example of where prior experience in making concrete
is beneficial. The concrete mixture can then be poured into wooden frames. These moulds
must then be covered and left to set for 2 days.
The second section of the construction process involves the production of the porous
concrete slab. The process is similar to the creation of normal concrete slabs as outlined in
section one. However, some aspects are slightly different. The major difference is based on
the consistency of the concrete. The porous concrete, as its name suggests must be porous
and thus must have larger gaps or voids within its structure. To achieve this, large pieces of
aggregate are mixed in with the cement instead of sand. Suitable aggregate needs to be
sourced and sifted to guarantee consistency, and mixed with a ratio of 1 cement : 4
aggregate. Once mixed, water will be added and stirred until the desired consistency is
achieved. A ratio of 0.4 water to every 1 bag of cement is an approximate guide. The porous
concrete mix must then be poured into a mould, covered and left to cure for 2 days, in a
similar was to the concrete slabs. If possible, it would be time effective for the labourers to
create both normal and porous slabs on the same day.
39
Water Purification In Cambodia 2008
The third section of construction is the process of sifting and washing of the sand to be used
inside the filter. As in the first two sections, all materials and equipment on the checklist
must first be located and collected. Initially, any sand must be acquired for use in the filter
and then sifted to ensure that only sand of consistent granularity will be used. The sifting
process can be carried out using a suitable piece of flywire with hole sizes as specified. The
sifted sand must then be washed thoroughly with water a number of times. Once cleaned,
the sand may be combined with the coal ash and mixed thoroughly. This new sand mix must
then be washed again to give the final product to be used in the organic stage of the filter.
The fourth section of the construction process delivers the finished filter. Once the required
tools and materials have been acquired the construction process may begin. The base slab
produced in section 1 can then be laid on level ground next to the well. The brickwork of the
filter can now commence. The labourers must then produce 4 layers of bricks in accordance
with the technical drawings and schematics they are provided with, with a small hole left in
the base of the filter at one side and filled with a piece of pipe to act as a backwash plug.
The labourers must ensure they use their level or set up string lines as they go and do not
leave any large gaps or openings as this would cause the filter to leak when filled. Following
this, the porous concrete layer can be included in the structure and bricking can continue.
The filter must then be rendered internally and externally to guarantee a water-tight seal. A
simple concrete mix, similar to the type used as mortar, would be suitable for this process. A
square trowel, or even hands, can be used to lather the mix on the filter.
The next step is to install the PVC pipe used to control the flow rate of the filter. Twentyeight 1/16 inch diameter holes must be hand drilled into the pipe to achieve the required
flow rate of 200L/h and the pipe must be cemented into place. A diagram, in Appendix
11.10 provides a clear explanation of where this pipe is to be located. Once the pipe has
been installed the 70kg of nails required to remove the arsenic can be included.
The sand and coal ash mixture can now be placed inside the filter. The mixture must be
poured into the suitable location and compacted down. Once this mixture is inside, the top
slab of the filter can be put in place and the concrete lid which covers the nails can also be
placed on top of the filter.
The pipe work connecting the filter to the well pump must now be installed as should the
taps. The labourers are then required to leave the filter for two days as the mortar and
render sets. Once the concrete has set the filter can be filled with water via the pump. The
labourers must then run a considerable volume of water through the filter to remove any
concrete or brickwork which was accidentally left inside the filter. The filter can be used
immediately, however, full effectiveness will not be reached until approximately two weeks
later because nails have to rust and the biological mass must grow.
40
Water Purification In Cambodia 2008
4.5 Materials Costing
Material
House Bricks
Plain steel
nails (not
galvanised)
Portland
cement
Sand
Plant Ash
Aggregate
UPVC Pipe
UPVC Pipe
UPVC Pipe
UPVC Right
angle
connector
UPVC End cap
Variable flow
tap
Specifications
Unit cost
230x115x75mm $0.30
Small as
$1.00/kg
possible
Quantity
492
70kg
Total Cost
$147.60
$70.00
No additive
$3.50/20kg
130kg
$22.75
Free
Free
Free
$70/6m
162L
40.5L
85L
900mm
Free
Free
Free
$10.50
$65/6m
1500mm
$16.25
$27/6m
300mm
$1.35
$4.95
4
$19.80
$1.90
1
$1.90
$5.00
1
$5.00
150mm
diameter, 4mm
thick
75mm
diameter, 3mm
thick
50mm
diameter, 2mm
thick
75mm
diameter
50mm
diameter
*Quantity may vary site to site. Responsible estimates are presented above
41
Water Purification In Cambodia 2008
4.6 Maintenance
The process of maintaining our filter is a simple procedure. In each village where a filter is
installed we plan to have one person tasked with the job of maintaining the filter. A
maintenance manual (provided in Appendix) will be supplied outlining the requirements and
responsibilities of the occupation. We plan to pay the worker a monthly wage depending on
money availability and demand for the employment. The maintenance worker will be
required to follow a number of steps as outlined in the manual graphically when the flow
rate from the output tap has stopped or decreased substantially.
First they must backwash the filter. The quick flow of water through the filter in reverse
removes any large particles or other blockages in the sand and coal-ash layers which may be
inhibiting the flow. To perform this backwashing the employee must remove the backwash
plug and allow the filter to empty. The worker will be made well aware that they are not to
drink this water as it is dangerous since it still contains pathogens and other water borne
diseases.
Following the backwashing the nails must be shaken and mixed in clean water. This process
will expose a new layer of iron to be rusted for the removal of arsenic as well as remove any
excess iron sludge covering the nails which may be blocking the filter.
So as to allow access to the nails the roof of the filter has been broken into two concrete
slabs, a large fixed top slab and a smaller concrete lid. The lid can be easily removed by two
average men exposing the nails. The nails can then be removed with a variety of tools. A
chisel, trowel and hammer would be ideal as the nails may be fused together. They will
have to be broken apart and removed, requiring some considerable force. Once removed
the nails will be placed in a large bucket of clean water, where they will be shaken and
stirred until the majority of the sludge has been removed. The nails will then be placed back
inside the filter and the lid replaced.
The worker must then refill the filter with the well's pump. This process will require a vast
amount of energy as the filter volume is large and will take a considerable time to fill. Once
full the filter should now once again produce clean, safe to drink water. If for some reason
this does not happen, the worker will have been instructed to repeat the process. If after
this, the filter is still not functional, the employee has been directed to contact Resource
Development International for further help.
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Water Purification In Cambodia 2008
5 Design Testing
To assist the design process and investigate the filter’s performance, extensive tests were
conducted on different aspects of the filter’s design.
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5.1 Arsenic Removal Test
To supplement the limited available data on the
efficiency of nail based arsenic removal, our group
performed extensive laboratory testing. These
tests involved several full day lab sessions to
investigate the amount of arsenic removed from
contaminated water. Our team consulted staff
from The University of Western Australia’s (UWA)
Centre for Forensic Science, School of Earth &
Geographic Sciences and School of Biomedical,
Biomolecular & Chemical Sciences and School of
Mechanical engineering. With the assistance of
several staff from across the university, our team
secured the necessary reagents, laboratory space
and analytical facilities necessary to perform these
tests.
For this investigation, a scaled down functional prototype of the arsenic removal stage was
constructed. Arsenic spiked tap water of varying concentrations was passed through the
filter, with samples of the pre and post filtered solution collected for lab analysis.
Left: Schematic diagram of test setup, Right: Team member collecting filtered water
Due to arsenic’s low concentrations compared to other contaminants, quantitative analysis
requires the use of sophisticated techniques or machinery. To perform the final analysis of
samples obtained from our test Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
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Water Purification In Cambodia 2008
was to obtain accurate results, with an estimated error of < 1PPB. A more complete
description of these tests is given in Appendix 11.7.
Solution
Mean
Pre Filtration
Mean Post
Filtration Arsenic
Concentration
% of Arsenic
Removed
Arsenic
Concentration
Solution A
<1 ppb
<1 ppb
N.A
Solution B
138 ppb
15 ppb
89%
Solution C
243 ppb
27 ppb
88%
Solution D
412 ppb
47 ppb
89%
Solution E
608 ppb
51 ppb
91%
Average Arsenic
Removed
Above: Inductively Couple
Plasma Mass Spectrometer
45
89%
The results from ICP-MS analysis indicated that an
average 89% of arsenic was removed from solution was
removed by the prototype. The data obtained from
these tests formed the basis of our choice to
incorporate 70Kg of nails in our filter’s design. In
addition to benefiting this project, these tests also gave
us the opportunity to practice analytical chemistry at a
level not usually available to undergraduates.
Water Purification In Cambodia 2008
5.2 Nail Rusting
The production of rust in our filter is essential to form the ferric hydroxide necessary for
arsenic removal. While it is understood that water and oxygen are required to generate rust
an iron surface, it was considered necessary to investigate how best to maximise the
production of rust in our design. The team investigated designs in which nails were:
a) totally submerged in water
b) partially submerged in water
c) suspended above the water
Three columns of nails, corresponding to choices a), b) and c) were placed in a bucket of
water. Water was run through the columns to investigate the volume of rust produced. The
conclusion of this test was that the nails suspended above the water produced more rust
than nails left totally submerged, and that the most rust was produced in the partially
submerged column. A full description of this experiment can be found in appendix 11.2.
The results of this test formed the basis of our decision to incorporate the nails directly
above the water line in our final design.
5.3 Porous Concrete Tests
During the initial stages of the design process, porous concrete was explored as a potential
filtration membrane. While our research suggested that porous concrete with a pore size of
0.1mm is sufficient to remove pathogens and turbidity from water, we were unable to find
sufficient data relating flow rate, pore-size and manufacturing techniques. While several
methods of manufacturing porous concrete were discovered, the majority required
ingredients and manufacturing processes which were considered unsustainable within the
context of the Kandal province.
A simple procedure for making porous concrete involves of combining cement and a coarse
aggregate such as gravel. Tests were conducted to investigate the pore-size and flow rate of
concrete produced in this manner. A full description of these tests is given in appendix 11.1.
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Water Purification In Cambodia 2008
Following the results of these tests, we concluded that porous concrete produced in this
manner will be insufficient to serve as a filtration membrane. We did, however, discover
that the material produced would be suitable for suspending a sand filter.
5.4 Flow Rate tests
The projected amounts of arsenic, turbidity and pathogens removed by our filter rely on
water flowing through at a specified flow rate. The filter consists of two stages in series, an
arsenic removal stage and a sand filter. The dimensions of the sand-filter were chosen to
sustain a larger flow rate than the arsenic stage, leaving the arsenic stage as the bottle neck
for water flow through the system.
In our design, the flow rate is limited by
forcing water leaving the arsenic stage to
pass through holes drilled into the bottom
of a PVC pipe. The size and number of
these holes is controlled to limit flow
through the system to a specified rate.
Appendix 11.4 provides a full description of an investigation that was conducted to
determine the size and number of holes required to achieve a flow rate of 200 L / Hour. As a
result of this investigation, we determined that 28 x 1/16 inch diameter holes are required
to achieve our desire flow rate.
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Water Purification In Cambodia 2008
5.5 Turbidity Removal
A second, partially functional prototype was
constructed. The 1/7 scale filter was
constructed using bricks, mortar, sand and
concrete. This allowed us to investigate the
filter’s construction process and to conduct
tests on the sand filter’s ability to remove
turbidity from water.
Turbid Water before (left) and after (right) passing through the sand filter
Turbid water was run through the sand filter stage and pre and post-filtration samples were
collected. Visual inspection revealed that the filtered water had very low turbidity. A taste
test was performed, with the output being indistinguishable from tap water. From these
test we concluded that the dimensions and composition of our sand filter would be
sufficient to remove turbidity from Cambodian water.
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Water Purification In Cambodia 2008
6. Implementation
‘… a number of the available arsenic and household purification technologies have serious
drawbacks, including complex production methods, high maintenance, high costs,
insufficient flow rate, and/or reliance on materials unavailable in remote villages. In
addition, most technologies treat arsenic and pathogens independently, resulting in
complicated treatment operations. Implementation deficiencies including ineffective
technology transfer, confusing [Non Governmental Organisation] responsibilities,
organizational non-sustainability, lack of user participation, and inadequate long-term
maintenance and monitoring capacity are other major causes of the non-sustainability of
water interventions…’
Excerpt from “Arsenic Kanchan Filter (AKF) – Research Implementation of an Appropriate
Drinking Water Solution for Rural Nepal” (Ngai et al, 2004)
The filter has been designed with the intention of sustainable, wide-scale deployment
throughout the Kandal province. The majority of capital can be obtained within the region,
with the exception of skilled labour such as engineers, which may need to be sourced
externally. Education, maintenance and monitoring procedures have been designed to
ensure that the filter continues to provide potable water to users over an extended period.
All raw materials are available within the province, with the majority obtainable from local
merchants and natural resources.
Before the filter is deployed, it will first be necessary to conduct a trial program to collect
more data on the filter’s performance, lifetime and cultural acceptance. This program will
involve the installation of a small number of filters in appropriate villages. Good candidates
for trial programs include villages with arsenic contaminated deep-bore wells that are
already suffering the effects of chronic arsenic poisoning. If successful, these trials will also
help to spread awareness of the filter and the water quality issues that it addresses.
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Water Purification In Cambodia 2008
6.1 Capital
6.1.1 Human Capital
Several key personnel are required for the deployment of our design. We have defined the
roles of project administrator, trainer, construction personnel, maintenance personnel, field
technician and engineering support. In practice, it is likely that multiple roles will be
allocated to a single person, for example, combining the role of field technician and
engineering support or administrator and trainer. To improve sustainability, it is an aim of
the project to maximise the number of roles filled by locals, although it is likely that the
more skilled roles will need to be filled by non-local staff.
The required skills and responsibilities of each role are as follows:
Administrator:
The administrator serves as the central point of contact between internal personnel and
external organisations. Their duties include communicating with sponsors, governments,
communities and support organisations such as RDIC and EWB. The administrator is also
responsible for managing the installation, maintenance & monitoring of filters , as well as all
data and documentation related to the project.
Trainers:
The trainer is responsible for the education of construction personnel. Their primary duty is
to conduct training workshops to impart the necessary skills. The trainer has detailed
knowledge of the construction and installation process as well as thorough understanding of
water quality issues, the project’s goals and the local community. This role could be filled by
an engineer with sufficient training and assessment skills.
Construction Personnel:
Construction personnel are responsible for onsite education and filter installation. As the
main point of contact between the project and villagers, they play a critical role in the
project’s success. Suitably skilled locals identified by administrators and trainers will be
offered employment and training via a practical workshop. After training, construction
personnel will have all the skills necessary to perform onsite installations of the filter.
Support Engineer:
It is the support engineer’s role to oversee the entire filter installation process. This person
has an in-depth understanding of the filter’s function and construction. During filter
installation, it is the engineer’s job to direct construction personnel, liaise with the
community and train one or more locals to perform low-level maintenance.
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Water Purification In Cambodia 2008
Maintenance Personnel:
During installation, the engineer will identify and train at least one villager to perform lowlevel maintenance and monitoring of the filter. This person will be responsible for observing
the community’s use of the filter and performing tasks such as cleaning or backwashing the
filter when necessary. During future visits by the field technician, this person will serve as a
point of contact for the community. Maintenance personnel will be offered a small stipend
for their assistance.
6.1.2 Physical Capital
The physical capital required for this project consists chiefly of the tools and resources
necessary for filter construction/installation. While they may not be available in each
locality, these common tools should be available within the Kandal province. Each
construction team will require a complete set.
Equipment
Cost
Hack saw
AU$6.00
Hand drill (not powered)
AU$20.00
1/16 inch drill bit x 2
AU$3.80
Square trowel
AU$25.00
Triangular trowel
AU$10.00
Wheel barrow
AU$55.00
Round mouth shovel
AU$32.00
Square mouth shovel
AU$9.95
5x 100L containers
AU$50.00
Timber planks for concrete moulds
AU$15.00
Measuring tape – 5 metre
AU$7.95
2
51
Fly screen 2x 1m
AU$7.95
Caulk Gun
AU$3.95
Silicone
AU$4.95
Builders level 1m
AU$5.95
PVC cement
$6.00
Water Purification In Cambodia 2008
6.2 Education
Education will play an integral role in the success of this project. We have identified three
groups of people that will require education in order for our design to be successful. These
are construction personnel, maintenance personnel and the end-users of our system.
Education will be assisted with the use of illustrated manuals to accommodate persons with
low literacy levels.
Education of Construction Personnel
As mentioned in section 6.1 of this report, construction personnel will receive education
during their attendance of a paid training workshop. The educational outcomes of this
workshop relate to understanding the project, the filter and the installation process. In
addition to these, there are several practical outcomes relating to materials selection &
filter construction. These outcomes will be assessed prior to the completion of the
workshop and construction personnel will not be dispatched to villages without having
demonstrated that they have achieved these outcomes.
Education Outcomes - Construction Personnel
Will demonstrate:
•
•
•
•
general knowledge of water quality issues related to arsenic and pathogens
a moderate understanding of the filter’s operation, including the importance of
flow rate and water proof construction.
ability to collect and prepare suitable sand, ash and gravel
ability to construct the filter
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Water Purification In Cambodia 2008
Education of Maintenance Personnel
As part of the installation process, the onsite engineer will be responsible for identifying and
training one or more villagers to perform basic maintenance of the filter. This is to ensure an
acceptable flow rate is maintained, which is essential for the community’s ongoing
acceptance of the system. The maintenance personnel will also be in charge of reporting the
community’s level of interesting in the filter, and relaying this information to the field
technician. Good candidates for maintenance personnel are villagers that are respected by
the community and show an appreciation of the filter’s purpose. Training will be delivered
via practical demonstration and one-on-one discussions with the engineer.
Education Outcomes – Maintenance Personnel
Will demonstrate:
•
•
•
general knowledge of water quality issues related to arsenic and
pathogens
basic understanding of the filter’s operation
ability to clean and backwash filter
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Water Purification In Cambodia 2008
Education of End Users
The most important group of people requiring education are the end users of the filter. This
includes both adults and children who will be using the filter to obtain potable water. It is
important for end-users to understand that not all water is potable and that the purpose of
the filter is to provide safe drinking water. When permanently attached to a bore-well
pump, obtaining water from the filter is nearly identical to obtaining water directly from the
pump. Emphasis will be placed on the necessity of using clean vessels to collect potable
water. The education of end users should be aided by community leaders and may take
place in a number of forums, such as public meetings, schools and small group
demonstrations. Should they exist, collaboration should also be sought with any hygiene
education programs being run by organisations such as RDIC.
Education Outcomes – End Users
Will demonstrate:
basic understanding of the filter’s purpose
ability to obtain clean water from the filter
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Water Purification In Cambodia 2008
6.3 Installation
It is the administrator’s role to identify candidate villages for filter installation. Factors that
should be considered are the presence of deep-bore wells, arsenic levels, availability of
other water sources and the community’s awareness of arsenic contamination. Prime
candidates would be villages where the symptoms of long-term arsenic exposure are
already present. A representative of the project will then conduct a site visit to discuss filter
installation with the community and gauge community acceptance of our system.
As this visit will be the first contact with the village, it is vital that care is taken to establish
an open forum for discussion with the community. A good relationship should be
established between our representative and the community’s leaders to allow open
discussion regarding the filter, its purpose and answer any questions the community may
have. The representative will report back to the administrator with recommendations as to
whether the filter will be successful in the respective community. Following a successful site
visit, the process of filter installation can commence.
Prior to installation, construction teams, consisting of 2 construction personnel and an
engineer, will acquire the raw materials. Sand, ash and gravel will be sourced from the land
and fireplaces, and the sand will be washed as outlined in the construction process. The
remaining materials are to be purchased from local hardware suppliers. The construction
team will then drive the materials to the village on a flat bed truck for installation.
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Water Purification In Cambodia 2008
Day 1
Set the moulds and pour the concrete slabs for the top and bottom. [2
hours]
· Survey ground and do necessary earth works and foundation works.
[2 hours]
·
Collect/smash aggregate and pour the porous concrete. [2 hours]
·
Further smash aggregate for under the pvc piping. [1 hour]
·
Cut and puncture holes in pvc pipe to be created. [3o mins]
· Start creating awareness in the community of what is happening,
start talking to people and making contacts with leaders of the
community. [Rest of day]
Day 2
·
Maintenance workshop training [4 hours]
Seminar on water health and general drinking practices [ 2 hours]
Day 3
· Filter and wash sand. Prepare ash and create mixture to be used in
filter. [3 hours]
·
Build the filter. Involves laying bricks, installing all fittings and
internally and externally rendering it. [6 hours]
Day 4
·
Open seminar outlining health practices concerning drinking water
and how the filter helps to remove theses. [ 2 hours]
‘Door knocking’ to engage more individual participation [6 hours]
Day 5
56
·
Put sand/ ash mixture in. Place nails inside. [1 hour]
·
Connect piping to bore and conduct basic tests. [2 hour]
·
Pack up and drive to next village [Rest of Day]
Water Purification In Cambodia 2008
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Water Purification In Cambodia 2008
6.4 Monitoring & Maintenance
As part of the installation process, at least one villager will be recruited and trained to
perform monitoring and low-level maintenance of filter. Monitoring includes noting the
community’s use of the filter, rates of illness in the community and the turbidity of filtered
water. This person will receive a small stipend per month, to be paid by the visiting field
technician.
Higher level monitoring and maintenance of filters will be conducted by visiting field
technicians. This will involve collecting data about the filter’s use via discussions with the
local maintenance person and community leaders. The field technician will also inspect the
filter for structural defects. During this visit, the technician will collect pre and post filtration
water samples for laboratory analysis to measure arsenic and pathogen levels. While we
have defined the role of field technician as part of our project, these duties may be
performed by RDIC staff as part of their water analysis program. All data collected from field
technicians will be recorded by the project’s administrator and made available to other
relevant organisations.
During a trial program, installations should be closely monitored, with technicians
performing site visits every 1-2 months. The data collected by field technicians will be used
to assess and improve the filter’s performance. Should the filter be deemed suitable for
wide-scale deployment, 1-2 visits per year should be sufficient to ensure that filters are
performing to specification.
6.5 Waste Management
We have managed to address issues of recyclability in our design. Recycling the bricks in out
filter significantly reduces the cost of building a new filter and thus makes the filters more
affordable in the long term. For recyclability purposes, the top slab can be broken up and
reused as coarse aggregate for new concrete, as can the porous concrete layer. It is possible
that a new filter will be built on the same sight as the one it is replacing and so the bottom
slab could be reused, if not, it can be recycled in the same way as the top slab.
Another important filter component is the bed of nails used in the arsenic stage. During the
lifetime of the filter, the nail mass will decrease. The extent to which this will occur has not
been properly tested, however, when rebuilding of the filter takes place, the remaining nail
mass can be cleaned and separated to allow new surface area to undergo reaction with the
arsenic. Due to the mass of nails being less than the desired 70kg, new nails can simply be
added to the amount remaining and so all waste from the original filter is being reused.
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Water Purification In Cambodia 2008
When the iron from the nails reacts with arsenic, it produces arsenic contaminated
sediment. Due to the dual chamber design of our filter, this sludge will collect at the
bottom. As a result of the mixture’s toxic nature, it must be disposed of in an
environmentally friendly manner as it is cannot be destroyed. Cement solidification is the
technique currently employed in Western Australia by Ortest Pty Ltd for arsenic waste
management (Environmental Protection Group, 1998). The process involves the
stabilisation and disposal of arsenic by reaction with cement. Lime in the cement reacts
with arsenite to form calcium arsenite, an insoluble precipitate. This precipitate is highly
insoluble at pH levels of between 10 and 11 and the large amount of lime ensure that a pH
value within this range. If the pH happens to drop below this level, the arsenic would leach
out very slowly; however, the “leaching rates are estimated in geological time frames”
(Environmental Protection Group, 1998). The process of cement solidification could easily
be applied to the arsenic contaminated sediment that is a waste product of our filter. The
sediment would simply have to be collected and mixed with cement. The concrete blocks
that result could either be buried in the ground or possibly used in the rebuilding process,
possibly as a foundation for a new filter.
The nails mentioned above are supported by several kilograms of brick chips. These should
not suffer any damage during the lifetime of the filter and so they can simply be washed and
then used again in a new filter. When washing takes place, the runoff water will have to be
collected and then disposed of in the same manner as the sludge. This is because as the
arsenic sediment falls to the bottom of the filter, it will have to pass over these brick chips
and thus their surface will have become contaminated with arsenic.
The final component of our filter is a mixture of sand and coal ash which is used in the
organic filtration stage. This mixture will contain an increased level of bacteria present due
to filtration and the biological mass. Once the sand is no longer saturated with water, this
biological layer will die and thus will not have any adverse affects on the area around where
the sand is placed. However, it is still possible that contaminant levels in the sand will be
elevated. Nevertheless, the amount of sand is small relative to the amount present where it
will be disposed. For example, if it were to be put back on the riverbed where it was taken
from, when the contaminated sand mixed with ‘clean’ sand, these levels would drop to
insignificant amounts. It is evident that all filter components have been selected in such a
way that waste management is not going to be an issue in the disposal or recycling of our
design.
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6.6 Project Costing
As we are addressing the problem on a community scale, we will be seeking sponsorship
from world aid organisations. Therefore, accurate costing regarding successful
implementation and integration will be necessary to obtain funding from such
establishments.
In order to present comprehensive costing, we have considered one-time costs and ongoing
costs for each filter that we install, as well as overhead costs that are independent of the
number of filters in operation.
Overhead costs:
As part of our cost scheme, we have considered autonomous project costs, such as the
wages of the project administrator and trainers, and the equipment to be available to the
construction team.
RDIC claim that any requirements regarding “administration and finance” can be covered by
their organisation. Similarly, their establishment offers staff with training in “construction,
mechanics and technical trades”. It is clear then that the overhead costs in our project are
nullified by RDIC’s competency in the relevant areas.
Equipment required by the installation team:
The costs with regard to construction equipment will include the price of a number of tools;
these are outlined in Section 6.1.2. The purchase of this equipment will add to the project
cost by $307.45
One-time costs per filter:
Another section of our cost summary is the one-time costs for each filter that is constructed.
These include the cost of shipping and manuals, and wages for construction personnel and
necessary engineers.
As mentioned above, RDIC is able to provide staff that are capable in a number of roles. Any
necessary engineers fall into this category. On top of this, we will need to pay construction
workers a fee for their labour. The average wage per month for construction work is US$70
(Labour Costings, 2008). As this phase of the process will most likely take 5 days, we will
have to pay each worker roughly US$11.70. Our design process states that three labourers
will be required to carry out the construction phase, placing the cost of employing a team to
perform the installation at US$35. Therefore, our expected expenditure on wages during the
construction process is US$35.
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Water Purification In Cambodia 2008
However, material and shipping costs are not embraced by RDIC.
Materials required for the structure:
Similarly, there will be costs with regard to the materials used for the construction of the
structure itself. Section 4.5 concludes that this will contribute to the project cost by $295.15
Shipping:
Transportation is an important factor in the total cost of building a filter. For each filter, the
cost of moving the material required and transporting of the workers will be different as
each filter will constructed in a different location. In order to provide an accurate
approximation of the shipping costs, some assumptions are necessary.
Assumptions:
•
•
•
•
•
The materials and workers will be sourced from within the Kandal province
The filter will be built at a location in the Kandal province
Fuel costs US$0.90/L and fuel consumption is 15L/100km
A single truck will be hired for each individual job
We will ignore the cost of insurance for the truck
Based on an upmarket car rental company offering truck hire for $30 per day, we have
made the assumption that it will be possible to obtain a car locally for considerably less. We
estimate this figure to be $10 per day. Also, the average distance between towns in the
Kandal province is approximately 25km. This will result in shipping costs for each filter
installation being $50 + $6.75 = $56.75.
Ongoing costs per filter:
The final section of our comprehensive cost projection deals with the ongoing costs of each
filter that is installed. This includes any maintenance or testing.
Maintenance:
As Section 4.6 outlines, we have developed a thorough maintenance plan and schedule for
each filter. We plan to train and employ one resident in each village where there is an
operational filter to carry out regular maintenance. On top of this, our budget will cover less
regular testing to be done on the filter.
As we are simply employing this on-site maintenance hand to carry out simple, low intensity
maintenance, we concluded that a fair wage was US$2 per month. One maintenance
employee will be adequate to fulfil this requirement, setting maintenance costs at US$2 per
month.
Additionally, we consider it an ethical requirement to provide adequate testing on a regular
basis. RDIC has the capacity to supply water testing equipment and personnel and hence
this will not add to the cost of our project.
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Conclusion:
It is clear then that a comprehensive project cost has been determined. With consideration
to all aspects of the design cycle, including one-time, ongoing and autonomous costs, we
have established that an investment of $6140.95 is required to launch this project in
Cambodia with 15 operational filters.
Autonomous Cost
$307.45
One-time cost per filter
$386.9
Total Cost for 15 Filter trial program = < $6500
62
Ongoing cost per filter
$2 per month
Water Purification In Cambodia 2008
6.7 Funding
The United Nations Children’s Fund, (or UNICEF), is one of the many mediums we could approach for
funding for our water filter. UNICEF was traditionally set up to assist countries that have faced
significant adversity due to World War 2. In recent times provide humanitarian and developmental
assistance to families in third world countries. (UNICEF 2008)
UNICEF works on improving different aspects of the family’s lives, for example water, environment
and sanitation. The water, environment and sanitation projects run in 90 different countries and all
form to be a part of the larger project named The Millennium Development Goal (Ki-Moon 2008).
This Goal is one that aims to halve the proportion of people without sustainable access to safe water
and basic sanitation. They work in conjunction with the World Bank and other aid agencies to work
on this project.
Our water filtration device fits perfectly into the vision that these agencies envisage for the
Millennium Development Goal. The investment that is predicted to fund the goal is currently at $15
billion a year, which is labelled as half of what the target is (World Bank 2008). If our water filtration
device is deemed a viable solution, becoming part of the Millennium Development Goal may be a
promising funding avenue.
Although the Millennium Development Goal is half way through their campaign (2000-2015), the
economic environment so far has been overall prosperous, a perfect environment for investment
(the main source of funding for the project) (World Bank 2008). However the future global economic
outlook is bleak; with developed countries already seeing diminishing growth levels. As the
development countries are the main source of the investment, the investment levels that have been
seen in the past undoubtedly will fall off.
Generally, third world countries weather global economic slowdowns better than developed
countries, due to their self-dependency, being net exporters and having low amounts of
globalisation. The program could possibly be implemented through government spending initiatives,
or assisting with the investment for the Millennium Development Goal initiative.
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7 Impact Assessment
Throughout the design process our team has thoroughly considered the full impact of our
design on local communities and initiatives to create a sustainable filter. Out team has
defined sustainability as the ability to coexist with the society in Kandal Province for an
indefinite period of time. This can be broadly divided into economic, environmental and
social areas. Economic sustainability refers mainly to funding of the filter to ensure initial
and ongoing costs are provided for the lifetime of the filters. Environmental impacts must
be identified and nullified to ensure self sustainability of the design. This includes the whole
design life cycle from material selection to disposal of waste and recyclability of the filter
once design life is achieved. Finally all social impacts on the community must be minimised
and considerable effort to encourage short and long term acceptance.
7.1 Economic Impact
The location of the distributors of the construction materials is important to the viability of
the project. All the materials for the filters are currently available in Cambodia and it is very
possible that key materials such as bricks and cement can be purchased locally. This
expenditure to the local market will support the local industry, especially if more than one
filter is produced in the same village. Moreover, the labour used in the construction process
will be locally obtained, again injecting economic activity into the local labour market. The
education system (as outlined in the ‘Education’ section of this report) is focused on
schooling locals with regard to the appropriate building techniques and maintenance
schedules that are required for the filter to operate correctly. The use of local labour and
materials is important in creating jobs and also in the establishment of the filter as an
important communal tool.
It is plausible to suggest that as the filter is going to be produced locally, and with local
materials, then the village people will feel more obliged to use and maintain the filter. The
filters allow individuals to take control of their own health and see the benefits of drinking
clean water, an essential aspect in our design being successful.
In the long term, our filter can be viewed as an economically viable addition to the deep
bore wells. After the initial costs arising from production costs and transport, the filter
requires low cost for continuous use. As seen in section 4.6 (Maintenance), the only
continuous costs during the lifetime of the filter are wages of maintenance personnel, and
field technicians who perform arsenic level tests. These wages are relatively low, hence
affirming the economic sustainability of our water filter.
In the long term, our filter can be viewed as making improvements towards a more
economical viable design. The injections into local communities attract a multiplier affect to
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Water Purification In Cambodia 2008
improve economic sustainability. After initial costs, little ongoing funding is required for
maintenance practises and rebuilding of the filter when design life is reached. These
economic occurrences demonstrate the ability of our filter being long term economically
sustainable.
7.2 Environmental Impact
One of our major goals was to ensure that our water filter has minimal impact on the
environment. As mentioned in the ‘Waste’ section of this report, all components of the
filter are either totally recyclable or can be returned to the place from which they were
originally taken. For example, all of the bricks used to make the outer structure can be
reused when a new filter needs to be built and the sand can be returned to local
riverbeds. Hazardous wastes, such as arsenic sediment, have also been considered and
their impact on the environment evaluated.
The materials we have selected to use in our design have been chosen with sustainability in
mind. The main issue was deciding whether to make the external structure from bricks or
whether to use concrete. Both of these materials act in the same way, they provide a
strong, watertight structure that is able to withstand the forces placed upon them when the
tank is full. In order to determine which material would be used in our final design, we
considered how they are manufactured. Bricks are constructed by setting pressed clay in
moulds which are then heated which concrete is made from cement, water and
sand. Cement has to be quarried, which uses a lot of energy and the general negative
environmental impact associated with quarries. Airborne pollution at quarries takes the
form of gases, noise, vibrations and dust. The process of manufacturing cement is also not
environmentally friendly, 5% of global man-made carbon emissions are a direct result of the
cement industry (WBCSD, 2002). When calcium carbonate is heated, it produces the
desired lime and carbon dioxide as a bi-product (EIA, 2008). At a time when carbon
emissions are taking a greater importance, we saw this as a reason to use bricks instead of
concrete for the filter walls.
When considering the construction process to build the filter, the construction site is limited
in size and thus its environmental impact in the long term will be minimal. As our filter has
been designed to be built in conjunction with deep well that are already in existence, the
filter site will be very close to the well pump. This means that a new site does not have to
be created, which could possibly harm the surrounding areas.
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Water Purification In Cambodia 2008
7.3 Social Impact
The success of the filter is overall dictated by the end user. The filter must be socially
accepted and this implies minimising or overcoming many of short and long term issues
identified. As the filter will be implemented in many different communities our team
anticipates a range of responses and all conceivable negative cases must be considered.
Water is vital for survival and ground bores account for 45% of Cambodia’s primary drinking
water source during the dry season (UNICEF 2007). A foreign object attached to their ‘life
source’ has been identified as a major short term problem. The connection between the
bore and filter is PVC pipe and can easily be vandalised by a single adult to re-establish the
direct connection with the bore. A large one 1 square metre brick and concrete box can
easily be seen as intimidating. To minimise the severity of the short term familiarisation
period, the education system provided to the community by the technicians will introduce
and inform users about the filter. A successfully delivered education program will replace
unfamiliarity with intrigue within the community and the model use by community leaders
encourages inital uptake.
The use of local labour and materials is important in creating jobs and also in the
establishment of the filter as an important communal tool. It is plausible to suggest that
should the filter be made by villagers with local materials, the village people will feel more
obligation and urge to use and maintain the filter. Encouraging and rewarding interest in the
construction process will also create a sense of ownership and involvement within the
community.
The test of our teams design and many other filter already in the world is the usage patterns
over a period of time. Many filters have failed to be utilised because of acceptability
concerning flow rate, maintenance practises and expense. The seamless integration with
respect to user friendliness minimises the likelihood of long term issue becoming a factor.
Instead of users pumping water straight into buckets and carrying back, water can be
pumped into the filter and then collected. No waiting times are incurred unless the filter is
empty and maintenance is only burdened on a financially compensated individual. The
turbidity removal of the sand filter will improve the aesthetic properties of the improve
satisfaction and acceptance of the filter.
Furthermore, we can see the implementation of our water filters increasing the knowledge
base of Cambodian communities. Once implementation is complete, there will be trained
technicians in every village and it is important for them to continue learning about the
filters. It has been discussed that it may be beneficial to establish a database through with
technician can communicate ideas that have been raised with regard to the water filtration
process. This database could be in the form of a website that is monitored by RDIC or
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Water Purification In Cambodia 2008
whichever organisation assumes responsibility for the ongoing success of our water
filtration technique in Cambodia.
With the associated health benefits gain of using the filter, there will be an increased
awareness about the importance of safe drinking practises. The filters allow individuals to
take control of their own health and see the benefits of drinking clean water, an essential
aspect in our design being successful. This may lead to improved health practises in other
parts of their life concerning water storage and sanitation.
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Water Purification In Cambodia 2008
8 Conclusion
The final two stage design solution given in this report has been concluded to be the best of
those considered to suit Kandal Province. Our team aimed to design a water filter capable
of treating water from an arsenic contaminated bore well at its collection point. The final
design satisfies this aim; it has been proven to remove arsenic to safe levels, those set by
the World Health Organisation, as well as pathogens and turbidity.
To reach our final design, vast amounts of research were undertaken and several concept
designs considered. Initial research was focussed on the current filtration solution, ceramic
water purifiers as implemented by Potters for Peace. We found a number of problems with
these filters that could not be eliminated while keeping the same design and so a new filter
design was necessary. It was important to evaluate the effectiveness of many filtration
techniques and consider the effectiveness, should they be implemented in Cambodia. This
eliminated many technologies and lack of technical data relating to porous concrete led to
the use of sand as the organic stage of our filter.
To find a system for the arsenic removal stage, we looked at a number of current arsenic
filters, primarily the Kanchan filter which makes use of iron nails. This idea was scaled up in
order to meet our goal of creating a filter that works at a well’s collection point. The two
filtration stages, arsenic and organic, then had to be combined in such a way as for them
both to work effectively. The best design was found to be a two chamber system with
arsenic removal followed by pathogen removal.
Our chosen design has been created with recyclability in mind as engineers around the
world are becoming more and more aware of the importance of this issue. One major issue
resulting from the final design was the arsenic sediment, a result of the arsenic reaction
with the iron nails. This toxic sediment could have forced a design change, however we
discovered a method through which this sediment can safely be contained within concrete
blocks. We further developed this idea by stating that these blocks could be used in the
rebuilding process, once one filter no longer has the required flow. Our design also allows
for a low-cost rebuilding phase as many of our materials can be recycled.
The appropriateness of our design for the Kandal province was considered throughout the
development of our design. This means considering the economic, social and environmental
context into which the filter will ultimately be introduced. For example, it is the belief of
many Cambodians that if water appears to be clean, then it is safe to consume. Hence our
filter needed to produce water that had good aesthetic properties. The filters ability to do
this was confirmed in tests using our prototype.
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Water Purification In Cambodia 2008
The lifetime of our design is 5+ years and we cannot find reason why it would fail before this
time. It is possible that simply adding more nails to the filter would increase this span
further. It is also possible that the filtration project will be funded by an organisation such
as RDIC or they could be integrated into current development programs such as UNICEF’s
Millennium Development Goal.
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Water Purification In Cambodia 2008
9 Reference List
Blicq D, 2008, Adhesives , Description of sources for adhesives, Available from 2008,
<http://xnet.rrc.mb.ca/davidb/examples.htm> [24 August 2008]
Brown J, Hill C, 2007 Effectiveness of Ceramic Filtration for Drinking Water Treatment in
Cambodia, Available from <www.edc-cu.org/pdf/joe+brown+dissertation.pdf> [15 August
2008]
Burch J, Thomas KE, 1998 An Overview of Water Disinfection in Developing Countries and the
Potential for Solar Thermal Water Pasteurisation, Available from
<www.osti.gov/bridge/servlets/purl/567490-HvB13u/webviewable> [1 September 2008]
Cambodia: A Small Market with Manufacturing Potential 2007, Available from
<http://info.hktdc.com/econforum/tdc/tdc071001.htm> [24 August 2008]
Cambodian Wildlife 2000, Available from
<http://www.asianinfo.org/asianinfo/cambodia/pro-wildlife.htm> [24 August 2008]
China steelmakers plan joint investment in Cambodia iron ore projects to cut costs 2007,
Available from <http://www.iht.com/articles/ap/2007/05/25/business/AS-FIN-ChinaCambodia-Steel.php> [24 August 2008]
Cuba G, 2005 In Bangladesh, Arsenic-free Water Set to Flow from Cheap New Filter, Natures
Medicine 11, 1128 Published online: 27 October 2005 [2 September 2008]
Dinesh Mohan, Charles U. Pittman Jr, 2007 Arsenic Removal from Water/Waste Water using
Adsorbents – A Critical Review, Journal of Hazardous Materials Volume 142, Issues 1-2, 2
April 2007, Pages 1-53 Available from <www.sciencedirect.com/science/article/B6TGF4MS3JB8-4/2/936f417f27121ad98fded4543ff3d> [17 August 2008]
Eurodia, 2008 Nanofiltration, Available from <www.eurodia.com/html/nab.html> [16
August 2008]
Exchange Rate 2008, Phnom Penh, Cambodia, Available from
<http://www.khmernews.com/exchangerate.asp> [24 August 2008]
Feldman, P. R. Rosenboom, J. W Saray, M. Navuth, P.Samnang, C.Iddings, S. 2007
Assessment of the Chemical Quality of Drinking Water in Cambodia, Journal of Water and
Health Vol 5; #1 pages 101-116
Fuwape JA, Akindele SA, 1996 Biomass Yeild and Energy Value of Some Fast –Growing
multipurpose Trees in Nigeria, Available from www.sciencedirect.com> [16 August 2008]
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Hagan, J. 2006 Materials Specifications and Costing EWB Available from
<www.ewb.org.au/ewbchallenge/files/Construction+Materials+2.pfd > [1 September 2008]
Hasslberger S, 2006 Low-tech Solar Water Purification: It works, Available from
<www.newmediaexplorer.org/sepp/2006/03/24/lowtech_solar_water_purification_it_work
s.htm> [16 August 2008]
Hillie T, Hlophe M, 2007 Nanotechnology and the Challenge of Clean Water, Available from
<www.nature.com/naturenanotechnology> [16 August 2008]
Hussam A, Muni A 2007 A Simple and Effective Arsenic Filter Based on Composite Iron
Matrix: Development and Deployment Studies for Ground Water of Bangladesh, J. Envrion.
Sci. And Health, Part A. Toxic/Hazardous Substances and Environmental Engineering,
Available from
<www.chemistry.gmu.edu/faculty/hussam/Arsenic+Filters/ESH+ARSENIC+FILTER+PAPER+20
07.pdf > [21 September 2008]
Irvine K 2008 An Overview of Water Quality Issues in Cambodia EWB Available from
<www.ewb.org.au/ewbchallenge/files/CHI+monograph,+Irvine+et+al+final.pdf> [29 August
2008]
Johnston R et al. 2008 United Nations Synthesis Report on Arsenic in Drinking Water,
Chapter 6 World Health Organisation Available from
<www.who.int/water_sanitation_health/dwq/arsenicun6.pdf > [29 August 2008]
Labour Costings 2008, Available from
<http://www.ewb.org.au/ewbchallenge/files/Labour%20Costings.pdf > [24 August 2008]
Legionella Control International, 2008, CFU or Colony Forming Units – Legiolnella Glossary,
Available from <www.legionellacontrol.com/cfu-glossary.htm> [17 August 2008]
Meng X, Korfiatis G, Band S, 2002 Combined Effects of Anions on Arsenic Removal by Iron
Hydroxides Toxicology Letters, Volume 133, Issue 1, pages 103-111 [27 September 2008]
Meng X, Korfiatis G, Bang S 2002 Removal of Arsenic from Water by Zero-Valent Iron Journal
of Hazardous Materials 121, pg 61-67 [1 September 2008]
Mushak P, 2000 Arsenic and Old Laws – A Scientific and Public Health Analysis of Arsenic
Occurrence in Drinking Water, Its Health Effects and EPA’s Outdated Arsenic Tap Water
Standard, National Resources Defence Council , Available from
<www.nrdc.org/water/drinking/arsenic/chap1.asp > [29 August 2008]
Ngai T, Murcott S, Dangol B, Construction, Installation, Operation and Troubleshooting of the
Kanchan Arsenic Filter (KAF) Gem505 Version
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<http://web.mit.edu/watsan/Docs/Other%20Documents/KAF/KAF_Construction_Manual_J
an2006.pdf> [30 August 2008]
Polya DA, Gault AG, Diebe N, Feldman P, Rosenboom JW, Gilligan E, Fredericks D, Milton AH,
Sampson M, Rowland HAL, Lythgoe PR, Jones JC, Middleton C, Cooke Da, 2005 Arsenic
Hazards in Shallow Cambodian Groundwater, Available from
<www.minmag.geooscienceworld.org/cgi/content/abstract/69/5/807> [16 August 2008]
Potters for Peace 2004, Filtron Ceramic Filter for Drinking, Available from
<www.pottersforpeace.org > [14 August 2008]
Shaw R, 1999, Running Water: More Technical Briefs on Health, Water and Sanitation.
Intermediate Technology, London UK p.103
Ray, CG 2004 Sherris Medical Microbiology 4th ed. McGraw Hill, unknown.
Ron Rivera 2004, Filtrón Ceramic Filter for Drinking, Potters for Peace, Available from
<http://pottersforpeace.org/wp-content/uploads/ideass-brochure-english.pdf> [14 August
2008]
UNICEF 2007, Use of Ceramic Water Filters In Cambodia, Available from
<www.unicef.org/eapro/WSP_UNICEF_FN_CWP_Final.pdf> [14 August 2008]
World Health Organisation 2008 Arsenic in Drinking Water, Fact sheet No 210, Available
from <www.who.int.mediacentre/factsheets/fs210/en/index.html > [29 August 2008]
Yamamura S 2001, United Nations Synthesis Report of Arsenic in Drinking Water, Available
from <www.who.int/water_sanitation_health/dwp/arsenicun5.pdpf > [29 August 2008]
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10 Acknowledgements
Our team would like to thank the following people and groups for their support and
assistance through the challenge.
Chris Rowles, GENG1003 tutor, Civil & Mechanical Engineering, UWA
For his support and encouragement throughout the project.
John Watling, Chemistry, UWA
For his generous advice and assistance regarding arsenic analysis.
Brad Stappenbelt, GENG1003 Unit Coordinator, UWA
For the support and assistance obtaining funds for water analysis.
Michael Smirk, School of Earth and Geographical Sciences, UWA
For his assistance regarding arsenic testing and water analysis.
Allen Thomas, Chemistry, UWA
For his assistance with water analysis.
Kevin Mavric and staff, Makit Bennett’s Hardware
For their generous provision of resources and facilities to construct our prototype filters.
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Water Purification In Cambodia 2008
11 Appendices
11.1 Concrete Tests
Porous concrete was initially considered as a cheap alternative filtration method to improve
turbidity and reduce pathogens. However research into the issue uncovered illusive and
contradicting details. The main issue presented was not of
biological capabilites but a definitve methodology to
source materials and construction instructions to create a
medium that was of known purification profeciency.
The aim of constructing porous concrete samples was to
examine flow rates, gain familiarty with concrete
construction methods that will be utilised throughout the
filter and if deemed necessary laboratory test some
samples.
Above: General purpose Portland Cement
Materials selected were chosen to be in line of what is typically available in Cambodia.
Regular portland cement with no addities is a commanly avaiable construction material as
depicted in the above photograph.
A selection of aggregate was used and in different ratios. The purpose of aggregate is to
create the void spaces which lead to the porosity. Using smaller size aggregate creates
smaller pore sizes leading to lower flow rate but increases its ability to trap microbiological
organisms. The composition of the agrregate is unimportant but rather the critical factor is
size and strength as the aggregate is what strengthens the concrete. Three different types of
aggregate were used as depicted in the pictures on the next page.
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Water Purification In Cambodia 2008
Above: The three aggregate sizes
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To familarise ourself with construction methods, moulds were constructed and tools used
inline with the resources Camboidan labourers would have. Any avaibale timber with one
straight edge can be constructed as the use of moulds. In our case 4 nails in each mould was
suffecient to hold its shape for mulitple uses. The mould was of approximately
270x160x50mm, For concrete poured in our final design, backing will also be required in the
moulds.
The only other materials required is sand, water, a shovel or mixing stick and
buckets/wheelbarrows to mix the concrete in. Black tarp was used in our case to provide
the backing of our moulds.
With collaboration of Steve Mueller from Cockburn Cement Pty Ltd and research already
conducted, eight different samples were tested, in a batch of five then a follow up sample of
three. Below is the following ratios by volume.
Test
Sample
1
2
3
4
5
76
Cement
Sand
1
1
1
1
1
2.5
2.5
2.5
0
0
Large
Aggregate
2
2
2
4
2
Medium
Aggregate
0
0
0
0
2
Small
Aggregate
0
2
4
0
0
Water
4
4
4
0.4
0.4
Water Purification In Cambodia 2008
6
7
8
1
2
1
0.5
0
0
2
2
0
2
2
4
0
0
0
0.6
0.8
0.4
The construction was competent and the ratios were strictly upheld too. 48 hours was
allowed for setting before water was ran through.
While permeability was observed in 4 of the 8 samples, the excessive flow rate was of
concern. The size of the pores and flow rate exhibit an inverse relationship. Especially
important is consideration of the Potters for Peace filter which has a 2-3L an hour flow rate
but works on the same principals. The large flow rate observed encouraged serious
consideration about whether porous concrete could match the pathogenic filtration abilities
of similar filters relying on the same principal like Potters for Peace. No calculations or
further testing was required to confirm our observations.
High doubt was present in the team about the plausibility of porous concrete as an organic
filter and the decision was unanimous not to pursue the technology any longer. However a
positive outcome from the experiment was the use of sample 4 to be used as a porous
medium to hold up the sand filter and the required construction methods to consistently
produce it.
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Water Purification In Cambodia 2008
11.2 Nail Rusting Tests
Objective
To investigate how the rate of rust production varies when nails are either
a) totally submerged or
b) left above the water level
Procedure
2 Kg of 'Bright', non-galvanised iron nails were split by volume into 4 equal portions
3 tubes were filled with nails with different amounts of gravel added at the bottom to
change the height at which nails sit above the water line.
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Water Purification In Cambodia 2008
The tubes were left to sit in a bucket, with water flow through them.
The nails in Column A were totally submerged under water at all times
The nails in Column B were partially submerged (half above the surface and half below)
The nails in Column C were completely above the water line
Over two days, water was run through the tubes for ~10 hours per day (to simulate real
use).
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Water Purification In Cambodia 2008
Results:
Column A (top), Column B, and Column C (bottom)
(Left to right) Column A, B and C
After two days there was the most rust in the partially submerged column(B), followed
closely by the above water column(C). The submerged column had very little rust(A).
Columns B and C had a fair bit of sludge, especially in the gravel layer.
Conclusion
Nails left exposed to air rust more quickly than nails left totally submerged.
The nails in the Kanchan filter are left exposed to air.
Our numbers for flow rate, arsenic removal efficiency and nail mass are based on those
from the Kanchan filter. If we choose to deviate from their design by leaving our nails totally
submerged, then those numbers won’t be valid any more. Since rust production is lower in a
totally submerged nail bed, we would have to compensate for this by etiher reducing our
flow rate, adding more iron nails or accepting a lower arsenic removal % efficiency.
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Water Purification In Cambodia 2008
11.3 Investigation of Sludge
The only operational waste product from our filter was the sludge from the rusting process
in the nails. Despite further research many unknowns remained about the properties of this
sludge that initiated an investigation. The aim was to determine the quantity produced and
aesthetics of the sludge as well as observationally observe properties like adhesiveness,
viscosity and fineness.
As part of our iron rusting experiment, our team accumulated a significant quantity of
sludge. While flow rate was not accurate within the design specifications flow rate, other
properties were still able to be observed. The sludge collected was collected from running
water over 2kg of plain steel nails for 20 hours.
Quantity
Aesthetics
Adhesiveness
81
Significant sludge was formed to suggest our team needs to incorporate
ways of managing and disposing accumulation of sludge. Our team
concluded that sludge levels will eventually restrict flow rate through
the organic stage of our filter and cause sedimentation along the
bottom.
The colour of the water as seen above will conflict with cultural values
adopted by Cambodian’s. A very effective turbidity filter will need to be
incorporated in our teams design to remove the sludge from the final
product.
A noticeable smell is present and an unpalatable taste is present even in
very small quantities. This further reinforces our requirements to
remove all ‘sludge’ from our final product to produce culturally
acceptable product.
One of the main purposes of the tests was to determine to likelihood of
sludge blocking holes over time. This was directly related to adhesive
properties of the sludge.
Water Purification In Cambodia 2008
Even on polished plastic surfaces removing the sludge was proved to be
hard and accumulation on all surfaces inside our filter was deemed
inevitable. This information was vital in our teams design selection
process. As a result our teams PVC method to control flow rate was
selected over more primitive methods of controlling flow rate.
The sludge was noticed to be moderately fine and easily unsettled when
water was passed over/through it. However when simulating the low
hydrological forces experienced by our design flow rate the sludge
remained largely unsettled.
Fineness
Filtering the sludge once with a bed sheet removed a significant amount
of sludge as demonstrated by the output product below This suggests
that particle size is great enough to be filtered out. There were some
larger flakes but a majority of the sludge remained as a powder.
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Water Purification In Cambodia 2008
11.4 Flow Rate Investigation
Conservation of Mass: The law of conservation of mass states that the flow rate in must
equal the flow rate out. The following equation is a representation of this.
Since flow rate is a measure of the flow through a certain area at a given velocity the above
equation can be rewritten as where A is the area and U the velocity.
Our filter requires an output flow rate of 200L/h. Conversion to is shown below.
1
1
200 200 5.56 10 1000 3600
To calculate the total area of the hole required we must assume a constant velocity U.
We can therefore assume that the flow velocity through the gravel and brick-chips is the
same as the flow velocity through the holes in the PVC pipe. We may consequently calculate
a value for the total area of holes required in the PVC pipe for a given flow velocity. A table
showing the area calculated using a variety of flow velocities is shown below.
5.56 10
Flow Velocity ( )
0.001
0.01
0.1
1
10
Total Area of Holes ( )
5.56 10
5.56 10
5.56 10
5.56 10
5.56 10
Summary:
•
•
•
•
•
For a velocity of 1mm/s the total area required is 5.56 10
For a velocity of 1cm/s the total area required is 5.56 10
For a velocity of 10cm/s the total area required is 5.56 10 For a velocity of 1m/s the total area required is 5.56 10
For a velocity of 10m/s the total area required is 5.56 10 Observation of the filter has lead us to believe that a reasonable flow velocity would be
about 1m/s.
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Water Purification In Cambodia 2008
When the flow rate was calculated experimentally at a flow rate of 200l/h the Area
determined was 28 holes with a 1/16 inch diameter. Conversion to a total area measured in
is shown below. To convert inches to metres have multiplied by 2.45/100
!"# 2.45
$% 28 $
5.16 10 4
16 100
4
The experimental Area coincides with a velocity value of
(")*+,- 5.56 10
1.08 5.16 10
This value is extremely close to our calculated value suggesting the filter will have a flow
rate of 200l/h for the 28holes of 1/16 inch diameter.
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Water Purification In Cambodia 2008
11.5 Prototype Construction
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Water Purification In Cambodia 2008
86
Water Purification In Cambodia 2008
11.6 Arsenic Testing
Aim of experiment: To obtain quantitative data on the arsenic removal capacity of rusted
nails
Description
A small-scale functional prototype filter was constructed to obtain quantitative data about
the amount of arsenic removed from contaminated water.
The prototype consisted of 3 plastic containers corresponding to the arsenic removal stage,
filter body and sand filter stages of the filter in development for the Engineers Without
Borders Challenge design project.
Water passed through a nail bed, a gravel bed and a sand filter before collection at the
device’s output.
Prior to the experiment, 12kg of 2mm diameter 25 mm steel nails were wet daily for 2
weeks to generate the required rust.
Nail Mass: 12kg
Measured Flow rate: 1.0 to 0.9 L per minute
Tap water spiked with inorganic arsenic was passed through the filter and samples were
collected for analysis.
Arsenic analysis was conducted with the assistance from The University of Western
Australia’s Centre for Forensic Science. Inductively Couple Plasma Mass Spectrometry was
used to determine the arsenic concentration of pre and post filtration samples.
Method
Stock solutions of concentrated Arsenite(As(III)) and Arsenite(V) were prepared from salts.
200 mg / L-1 arsenite(As (III)) stock solution was prepared by dissolving As2O3 in 20% w/v
NaOH and neutralised with concentrated sulfuric acid until universal indicator pH = 7.
200 mg / L-1 arsenate solution was prepared by dissolving Na2HAsO4.6H2O in deionised
water.
From the stock solution 5 x 40L dilute arsenic solutions were prepared with the following
concentrations:
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Water Purification In Cambodia 2008
Solution
Volume of
tap water
40 L
40 L
40 L
40 L
40 L
A
B
C
D
E
Vol of As(III)
(200 μg / mL-1)
0 mL
10 mL
20 mL
30 mL
40 mL
Vol of As(V)
(200 μg / mL-1)
0 mL
10 mL
20 mL
30 mL
40 mL
Total Arsenic
concentration
0 μg / L
100 μg / L
200 μg / L
300 μg / L
400 μg / L
Each stock solution was passed through the filter, with pre and post filtration samples
collected for each solution.
Samples were stored overnight and taken to UWA’s Chemistry building for analysis the
following day. The ICP-MS was cleaned and calibrated as against laboratory standards and
blanks. Prior to analysis, samples were diluted to bring the arsenic concentrations within
optimum range for analysis.
The ICP-MS provided raw ion counts for all ions with a mass to charge ratio(m/z) of 75,
corresponding to the most abundant isotope of arsenic. However, the determination of
arsenic concentrations by ICP-MS is complicated by interference from ArCl- ions present in
the plasma, which also have an m/z of 75. With the assistance of staff from the Centre for
Forensic Science, the raw data was corrected using standard isotope ratios to determine a
total concentration of arsenic present in each sample.
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Water Purification In Cambodia 2008
Results:
Results from ICP-MS Analysis:
Inductively Couple Plasma Mass Spectrometry Results
Sample
Number
Sample
Description
Arsenic Concentration
(PPB)
Solution A
S01
Pre filter blank
0.7
0 ppb
S02
Post filter blank
0.6
Arsenic
S03
Post filter blank
0.6
S04
Post filter blank
0.7
Solution B
S05
Pre filter 100ppb
149.4
100 ppb
S06
Pre filter 100 ppb
127.2
Arsenic
S07
Post filter 100 ppb
15.5
S08
Post filter 100 ppb
13.4
S09
Post filter 100 ppb
15.0
Solution C
S10
Pre filter 200 ppb
234.6
200 ppb
S11
Pre filter 200 ppb
252.2
Arsenic
S12
Post filter 200 ppb
30.6
S13
Post filter 200 ppb
23.5
S14
Post filter 200 ppb
26.1
Solution D
S15
Pre filter 300 ppb
424.4
300 ppb
S16
Pre filter 300 ppb
399.0
Arsenic
S17
Post filter 300 ppb
49.0
S18
Post filter 300 ppb
52.5
S19
Post filter 300 ppb
39.1
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Solution E
S20
Pre filter 400 ppb
608.7
400 ppb
S21
Pre filter 400 ppb
607.4
Arsenic
S22
Post filter 400 ppb
54.6
S23
Post filter 400 ppb
52.4
S24
Post filter 400 ppb
47.1
Summarised of ICP-MS results
Solution
Mean Pre Filtration
Arsenic
Concentration
Mean Post Filtration
Arsenic
Concentration
% of Arsenic
Removed
Solution A
<1 ppb
<1 ppb
N.A
Solution B
138 ppb
15 ppb
89%
Solution C
243 ppb
27 ppb
88%
Solution D
412 ppb
47 ppb
89%
Solution E
608 ppb
51 ppb
91%
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Arsenic Filtration Results
650
600
E = 602
550
500
450
D = 412
400
350
Arsenic Concentration (ppb)
Pre Filtration Arsenic Concentration (ppb)
300
Post Filtration Arsenic Concentration (ppb)
250
C=243
200
150
B= 138
100
D = 47
50
B = 15
A=0
E = 51
C = 27
0
0
1
2
3
4
5
6
Test Run
Graph showing the pre and post filtration arsenic concentrations of solns A, B, C, D, E
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Analysis of results
Arsenic Concentration of
Pre Filtration vs. Post filtration Samples
60
50
2
R = 0.9461
40
Post concentration = 0.0888 * Pre-concentration + 3.2134
Post Filtration Arsenic
Concentration (ppb) 30
Arsenic Filtration Results
20
10
0
0
100
200
300
400
500
600
700
Pre Filtration Arsenic Concentration (ppb)
Graph showing the arsenic concentrations of pre and post filtration samples. The gradient of
the line of best fit indicates (1.0 – 0.0888) * 100 = 91.22% arsenic removal.
The data obtained from ICP-MS analysis using laboratory standards and blanks suggested
that margin of error in analysis is <1 ppb. The mean results obtained from our solutions
indicate that in all trials, ~90% of dissolved arsenic was removed from solution. While there
was a small reduction in flow rate throughout the tests, as the sand filter became blocked
with rust particles, this was measure to be less than a 10% variation from the initial flow
rate.
Conclusion
The results of this experiment indicate that 12Kg of nails are sufficient to remove 90% of
dissolved inorganic arsenic from tap water when passed through at a rate of 1 L per minute.
This suggests that 40Kg of nails should be sufficient to achieve 90% arsenic removal at our
required flow rate of 200 L per Hour.
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11.7 User Manual
1.)
Pump Water
2.)
Place Clean Bucket Beneath Tap
3.)
Turn On Tap
4.)
Turn Off Tap
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11.8 Maintenance Manual
MAINTENANCE MANUAL
If filter is not producing water follow these steps.
The inside of the filter looks like this
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Remove Backwash Plug and wait until no water comes out.
DONT DRINK
1.) Remove Concrete Lid
2.) Remove Nails and place in bucket of CLEAN water
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3.) Shake nails around in bucket for 5 minutes.
4.) Put nails back in filter
5.) Put Concrete Lid Back
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6.) You must now refill the filter with water. Pump water in using
the pump until when turn tap water comes out
7.) If you cannot get water to come out of tap, repeat steps 1-7.
8.) If water still does not come out contact Resource Development
International (RDI)
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11.9 Construction Manual
CONSTRUCTION MANUAL
This manual is designed to be used in conjunction with a set of technical drawings. The
technical drawings will provide all measurements and dimensions of the filter. This
manual will provide you with a graphical description of the process and will break the
construction process up into a number of easy to follow steps. The steps are grouped
together in four main sections, each of which is explained below.
To build this filter one of the workers must have prior brickwork and building
construction experience. One experienced worker will be enough though, they will
easily be able to explain and teach the process to others.
A checklist of the equipment and materials required for construction is set out below.
Section 1:
Materials: Cement
Sand
Equipment: Wheelbarrow
Water
Shovel
Bucket
Tarpaulin
Wooden Frames
Section 2:
Materials: Cement
Sand
Equipment: Wheelbarrow
Water
Aggregate
Shovel
Bucket
Tarpaulin
Shovel
Bucket
Flywire
Water
Aggregate
Wooden Frames
Section3:
Materials: Sand
Water
Equipment: Wheelbarrow
Coal Ash
Section 4:
Materials: Cement
and
Products of sections 1-3
Equipment: Wheelbarrow
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Shovel
Nails
PVC pipe
Taps
Bucket
Trowel
Level
Water Purification In Cambodia 2008
Section 1: Concrete Slabs
Collect the equipment and supplies required for slab construction. Check you have
everything with the checklist.
Mix the sand and cement with a ratio of 1 cement to every 4 sand in the wheelbarrow or
a bucket. Add water and mix until desired texture is achieved. A skilled labourer will be
able to tell you when this occurs.
Pour the concrete into wooden frames provided. Cover the moulds and leave to set for 2
days.
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Clean equipment used with water so no concrete left on bucket and wheelbarrow
After 2 days remove moulds from the frames, leaving the finished concrete slabs.
.
Section 2: Porous Concrete
Collect the equipment and supplies required for slab construction. Check with checklist
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Sift Aggregate so only large bits remain.
Mix the sand and large aggregate with a ratio of 1 cement to every 4 aggregate.
Add water to the aggregate mixture with an approximate ratio of 0.4 water to every 1
sand. Mix again until the desired texture is achieved.
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Pour into the wooden frame provided. Cover the mould and leave to set for 2 days.
Clean equipment used with water so no concrete left on bucket and wheelbarrow
Remove porous concrete slab from mould after two days.
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Section 3: Cleaning sand for filter
Collect the equipment and supplies required for slab sand cleaning. They are Sand,
Wheelbarrow, Coal Ash, Flywire, Bucket and Water.
Sift the sand through the flywire
Remove waste left behind in flywire from sifting and wash remaining sand with water.
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Mix the cleaned sand with coal ash and wash again.
Section 4: Filter Construction
Collect the materials and equipment required for construction. They are the concrete
slabs, porous concrete and sand mix already produced. You will also need bricks, more
cement, a wheelbarrow, water, level, trowel and more sand. Check against checklist.
Prepare foundation. Clear an area of land near village pump of required size for the
water filter (In our case a wooden pallet.) Compact the area place the base slab on top.
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Lay the first level of bricks. Make sure to use a level to ensure a constant height. A
schematic diagram is shown with the required finish.
Leave a space at the bottom for the drainage or backwash plug.
Space for Plug
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Continue laying bricks on top of first layer until 4 layers of bricks are complete. Make
sure to continue using level so as to ensure an even finish.
Start making the out cut for the porous concrete layer. The porous concrete slab will sit
on top of the fourth brick layer.
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Mud up under and around the porous concrete slab and place in
Lay bricks on top of porous concrete and continue to build to desired height as given in
technical drawings. An approximate guide is 14 bricks.
At appropriate layer leave half brick space for taps
Attach tap to PVC pipe using PVC cement. Drill holes in pipe and insert galvanised nails
to prevent rotation. Place pipe and tap system, in gap left previously for bricks.
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Internally and externally render the filter with concrete using your hands and a trowel.
Cut the PVC pipe to length and place inside filter. Mortar up around the gaps
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Insert the nails
Put Sand/Ash inside the filter
Place Top Concrete Lid On
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Connect pipe work up to the pump well. A combination of PVC pipe and PVC cement
should be used to connect the pump outlet to the filter input.
Run Water through for a while
Clean all tools used and remove any excess materials left over from construction.
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11.10 Distillation Experiment & Costing
The aim of conducting a distillation experiment was to determine practically the energy
requirements in the distillation process, which encapsulates efficiency losses. While
such quantities are theoretically easy to obtain, compensation for efficiency is
ambiguous. A final value in terms of kilograms of wood will provide the most relevant
unit of measurement when considering Cambodia’s current practises.
The test bench was chosen as a gas stove. The energy expenditure is precisely
controlled at a known value. The distance and from the water to heat source is
appropriate to simulate energy losses and convention currents surrounding the flame
are unrestricted to allow for real word energy losses. The test set up is illustrated
below.
Starting Volume of
Water (L)
Final Volume of
Water (L)
Water Boiled Off (L)
Time Elapsed (hour)
Energy Input
(MJ/hour)
Steam/hour
(L/hour)
Energy/Litre Boiled
(MJ/L)
Time to Distil 12L of
water (hour)
Energy to Distil 12L
of water (MJ)
111
Data 1
Data 2
Average
2
1
-
1.375
0.21
-
0.625
.5
34
0.79
0.5
34
-
1.25L
1.58L
1.415
27.2
21.52
24.38
9.6
7.59
8.59
326.4
258.24
292.32
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While consecutive test results varied by 26.5%, this can be attributed to the different
starting volumes and as a result the larger energy requirements to bring a bigger volume of
water to different stages of latency. We believe a distillation unit would be used on a per
demand basis so an average of 1 and 2L initial volume is adequate reference data.
Burning wood generates 21.6 MJ/kg of heat (Fuwape and Shadrach – 1999). An average
household of 5.9 people (UNICEF -2007) each requiring 2L of water per person for drinking.
Assuming that efficiency losses in the experiment represent the real life efficiency losses, an
average household will require 13.53Kg of wood a day to provide enough distilled water.
The benefit of distillation is the comparative unit cost and maintainability. No ongoing
service is required, and only routine cleaning in order to prevent the build up of substituents
left behind. We conservatively estimate a life span of 5 years before corrosion becomes an
issue of concern.
Material
Cost (US cents)
Cost Per Unit (cents / unit)
Labour - Manufacturer
70 000 / month
1.72
Kettle / Metal Pot
200 /each
200
Water Pipe (42x34)
50
50
Welder Electrode
20
20
Welder and Set up
900 000
18
This results in a unit cost of US$2.89. However, the unit cost is insignificant compared to the
costs of fuelling the stove if firewood is not freely available or collection a time consuming
activity.
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11.11 Reasons for Arsenic Contamination
A variety of data analysis has observed relationships between arsenic occurrence and
environmental and geographical occurrences. Observations have found that the highly
populated area between the Mekong and Tonle Bassac rivers are highly affected by arsenic.
Studies conducted by Stanford University of select wells measured monthly, inclusive of all
depths, showed no significant temporal variations (Polizzotto et al - 2005). See figure 69.1
for experimental results. The author concludes that arsenic contamination varies spatially
but not temporally.
Temporal Variantion Source: (Polizzotto et al - 2005)
Arsenic seems to be more common close to major water ways. The same Stanford
University study observed high occurrences of arsenic close to the Mekong River, however
further from the river you go, concernable levels of arsenic contamination is only found in
deeper wells (>45m). The average depth of arsenic-affected household and community
wells was approximately 40 metres (Feldman et al – 2006).
Rivers to the south and southeast of Phnom Penh which is largely situated in the Kandal
Provinace show the highest levels of arsenic contamination. The main aquifer blanketed by
this region is the grey Holocene aquifer that’s sedimentology and water chemistry has large
similarities with arsenic ridden areas in Bangladesh. Major cation analysis suggests
progressive changes in age and origin of groundwater moving from the river inland
(Polizzotto ML - 2005).
The Holocene aquifer is characterised by high levels or iron and manganese. The other
critical characteristic is the strong reducing conditions in the aquifers which leads to
reductive dissolution of abundant iron oxides in the sediment, together with trace metals
such as arsenic (DPHE/BGS/MML 1999). Monsoonal conditions seasonally alter water levels
which catalyses wide swings in reduction and oxidation process within the soil. Widespread
flooding associated with these seasonal conditions result in anaerobic soil conditions which
subsequently results in reduction of iron (hydr)oxides and sulfate. A supplementary theory
to the reducing capabilities of the aquifer is decomposition of alluvial and deltaic sediments
of the Quaternary age soil compounded by low ground water flow velocities (Nickson et al.
2000; Smedley 2003; Feldman et al - 2006).
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Reducing conditions together with high iron and manganese levels are commonly present in
areas of high arsenic contamination, statistical correlations are only moderately strong. Data
from WHO study also measured occurrence of common elements in water samples.
Correlation between arsenic and iron was a significant 0.37 and so to was the correlation
between arsenic and reduction-oxidation potential (Eh) being -0.42. Also higher arsenic
concentrations were noticed in areas with high pH. The authors concluded “Data from these
more recent tests suggest that the areas of greatest arsenic contamination risk are in the
vicinity of major surface watercourses and/or areas underlain by Quaternary-age
sediments... highest risk of arsenic occurrence appears to be near major drainages and/or in
areas where the surficial geology is dominated by Holocene age sediments” (Feldman et al 2006).
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11.12 Water Borne Diseases
Access to clean water is one of the major factors contributing to water borne diseases, along
with water storage contamination and insufficient levels of hygiene. Water borne diseases
are defined as bacteria, viruses and other parasites contracted by consumption of water.
74% of all deaths in Cambodia are related to water borne diseases (RDI – Cambodia) and
diarrheal diseases (chiefly Cholera) being the number one cause of death and disease in
children (NIS 2000).
Asiatic cholera, Vibrio cholerae or more commonly Cholera is a particular aggressive
bacterial type of Gastroenteritis which is considered an epidemic in Cambodia by the
UNICEF. Its symptoms are profuse watery stool which cause the onset of severe
dehydration. Malnutrition is catalysed which increases the susceptibility of other diseases as
well as increasing the severity of the symptoms of diarrhoea. Cholera may cause the onset
of death in as little as 3 hours of symptoms being present without treatment (Ryan KJ 2004)
but more commonly results in death of Cambodian children within 1-2 days of the onset of
symptoms (UNICEF – 2007). Given sufficient fluids most healthy people can make a full
recovery.
Escherichia coli more often known as E. Coli is a mostly harmless bacteria strain commonly
found in the lower intestine of warm blooded mammals. E Coli is widely used as the main
quantitative measurement for bacterial contamination of a water source and its presence
normally indicates additional biological activity. Most viral strains of the bacterium results in
food poisoning and results in no more than a bout of diareahoa to a health human being.
Particular strains O157:H7 or O111:B4 can cause serious illness or death in the elderly, the
very young or the immune deficient.
Hepatitis A is an acute infectious disease of the liver. The virus is spread by the fecal-oral
route and has a transmission process similar to E. Coli. The most common transmission
process in Cambodia is a person’s hands coming into contact with faeces then into direct
contact with water supplies, water storage reservoirs or food. Symptoms include loss of
appetite, nausea, diarrhoea, pain in the liver and Jaundice. Symptoms commonly last several
weeks but most people make a rapid recovery with a mortality rate of less than 0.5% on the
western world.
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11.13 Arsenic Health Effects
Many deeps wells situated in the Kandal province are contaminated by naturally occurring
arsenic which has adverse effects on the long term health of Cambodian’s. Arsenic is a
ubiquitous element found abundantly in earth’s crust. Arsenic weatherd rocks and soills are
eroded and absorbed into ground water supplies. Cambodia’s per capita fish supply for food
was 20kg per annum (that earthworks link) which contains levels of arsenic varying from 0.2
to 320 ppm (Lenntech Organistation). Consumption of arsenic through the skin is minimal
and is primarily contaminated by ingestion.
Inorganic arsenic can be found naturally as pentavalent arsenate (As(V)) or Arsenate
(As(III)). Although As(III) is more toxic, human metabolic systems chemically reduce As(V) to
As(III) before undergoing detoxification by methylation (Smith et al 1992). Shortly after
arsenic contamination traces can be found in the liver, lungs and digestive systems. Most
arsenic is the then discharged naturally however traces may be found in skin, hair, nails, legs
and teeth (Lenntech Organistaion).
Acute or short term affects of Arsenic include nausea, oesophageal, cardiac arrhythmia and
diareahoa. Oral intake of more than 100mg is fatal however the concentration of arsenic in
ground water supplies is relatively dilute and lethally high concentration of arsenic is
nonexistent in water supplies. Long term consumption of arsenic leads to the chronic
condition Arsenicosis. The symptoms of Arsenicosis are less specific and vary between
individuals, populations and geographic areas. Typical symptoms are thickening
(hyperkeratosis) and changing pigmentation of skin, stomach pain, depression, sleeping
disorders, hallucinations, 116iarrhea, partial paralysis, spontaneous abortion and blindness.
However the primary concern is a cancer which is a late occurring phenomia commonly
taking over 10 years to develop.
The most prominent formation of cancers are of the skin, lungs, urinary bladder and kindey.
“On the basis of overall consistency of results from epidemologcal studies, there is
persuasive evidence that inorganic arsenic is a cause of human cancer at several sites.
“(Smith et al 1992).
Due to the primitive medical facilities and expertise in Cambodia the onset of chronic
cancers usually results in death. Arsenic is being widely regonised as a carcinogen and toxic
substance. Attached is a table adopted from Natural Resource Defence Council 2001 and
Smith et al 1992.
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Water Purification In Cambodia 2008
Arsenic Level in Tap Water
Approximate Total Cancer Risk
(in parts per billion, or ppb) (assuming 2 liters consumed/day)
0.5 ppb
1 in 10,000
1 ppb
1 in 5,000
3 ppb
1 in 1,667
4 ppb
1 in 1,250
5 ppb
1 in 1,000
10 ppb
1 in 500
(WHO Acceptable Level)
20 ppb
25 ppb
50 ppb
Being Married to a Smoker
1 in 250
1 in 200
1 in 100
1 in 100
(passive smoking)
Average Exposure of Radon
1 in 333
in homes
(table adapted stolen from http://www.nrdc.org/water/drinking/qarsenic.asp based on the
National Academy of Sciences' 1999 risk estimates and Smith et al 1992)
According to (Irvine et al 2008) a 2002 study found that the average arsenic content of wells
tested in the Kandal province was 178 parts per billion (ppb) which extrapolating the data
corresponds to a 1 in 28 chance. However the authors go on to postulate ‘This simple
summary underscores the risks. Many wells do not contain any arsenic and where it is found,
it can exceed 500 μg L-1.’
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11.14 Technical Sketches
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124