1

Cambodia: Arsenic Removal

from Drinking Water through a Variety of Options Molis O’nilia Nou

FEBRUARY 2016

ARSENIC

MITIGATION

OPTIONS

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1 INTRODUCTION

Table of Contents

1 Introduction ..................................................................... 1

1.1 Problem Statement ..............................................................................1

1.2 Background on Cambodia ...................................................................1

1.3 The Solution ........................................................................................ 2

1.4 Aims and Objectives ............................................................................2

1.5 Significance of Research ..................................................................... 2

2 Literature Review ............................................................ 3

2.1 Arsenic Contamination in Groundwater ...............................................3

2.2 The Cambodian Context ...................................................................... 5

2.3 Factors to Consider in Water Filtration Design ................................... 11

3 Arsenic Mitigation Options ........................................... 12

3.1 Arsenic Mitigation Techniques ........................................................... 12

3.2 Existing Projects in Cambodia ........................................................... 14

3.3 Projects Outside of Cambodia ........................................................... 16

3.4 Overview of Existing Arsenic Mitigation Projects .............................. 20

4 Recommendations ........................................................ 23

5 Conclusions ................................................................... 24

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Executive Summary

The research paper investigates a variety of filtration technologies and

systems for producing drinking water that is safe for human consumption.

The purpose of the research is to provide background information and a

review of existing literature that could potentially be used to design a water

filtration system for locals in Cambodian provinces such as the Kandal, Prey

Veng and Kampong Cham provinces.

The two primary sources of drinking water in Cambodia are groundwater

and surface water with groundwater being particularly prone to

contamination by arsenic. Hence, the research focuses on mitigation options

for the removal of arsenic from groundwater. Arsenic contamination has

been linked to various health problems including skin lesions and skin

cancer

This research paper describes 5 different arsenic removal technologies that

exist as well as practical applications of these technologies. From these

technologies, it was recommended that a household or community scale

design for a water filtration system should be used given the poor economic

state of the aforementioned Cambodian provinces.

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1 INTRODUCTION

1.1 Problem Statement

Whilst the vast majority of people living in developed countries have abundant access to

clean water supply, with an average of 90% of Australian’s having access to clean drinking

water, this is not the case for most developing nations (Sydney Water 2014). In particular,

access to clean water supply is a major issue in Cambodia. Although copious amounts of

water exist, from the two converging rivers, the Mekong and the Tonlé Sap, that flow across

Cambodia, to the 16 km of ocean water that borders Cambodia, much of it is contaminated.

During monsoonal season, both the Mekong and Tonlé Sap River serve as the primary

source of water supply in Cambodia and as rivers drain and the dry season arrives, locals

turn to groundwater extracted from wells. Among these water sources, groundwater presents

issues discovered only in the past two decades. Rivers are often used for washing pets as

well as clothes and household appliances resulting in bacteriological contamination.

Statistics have emphasised the significance of bacteriological contamination in rivers where

86% of deaths in Cambodia were related to preventable waterborne diseases in 2014 (RDIC

2014). In the case of groundwater, a study has shown that 73% of groundwater extracted

from wells along the Mekong and Bassac river banks contain high levels of naturally

occurring arsenic, exceeding 10µg/L, a guideline set by the World Health Organisation for

safe arsenic consumption (WHO 2014). Up to 1340 of arsenic per litre of water has been

recorded along these banks and a survey have shown that 1 in 10 people who drink water

containing 500µg of arsenic per litre of water may ultimately die from cancers caused by

arsenic including skin, lung, bladder and kidney cancers after long term consumption (A. H.

Smith 2004 and Buschmann et al 2007). There have been a number of efforts focused on

the removal of pathogens, however little has been done to address arsenic contamination.

1.2 The Solution

An affordable yet efficient water treatment system is essential to address the issue of

bacteriological and arsenic contamination in groundwater and ensure freshwater supply is

met across Cambodia, as well as other countries in the same situation.

1.3 Background on Cambodia

Cambodia, officially known as the Kingdom of Cambodia, is a country located in the

southern portion of the Indochina Peninsula in Southeast Asia. It is bordered by Thailand to

the northwest, Laos to the northeast, Vietnam to the east, and the Gulf of Thailand to the

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1 INTRODUCTION

southwest and has a landmass of 181,035km2. With a steadily increasing population and

economy of over 15 million people and GDP of $39.7 billion, respectively, Cambodia once

saw a very traumatic past (IEC, 2013). Led by Pol Pot, the Khmer Rouge regime rose to

power in 1975 and killed approximately a quarter of the population leaving Cambodia in

social and political distrust. At present time, the aftermath of the war has caused major

problems including lack of adequate water, sanitation and hygiene, education,

transportation, and communication. The most common diseases in Cambodia today are

related to problems with water and sanitation (WHO, 2014). Many initiatives for national

development have been employed and in particular within the water sanitation sector.

1.4 Aims and Objectives

The primary aim of this research paper is to assess the suitability of existing arsenic

mitigation technologies to provide safe drinking water to locals in small communities across

Cambodia. Achieving this objective requires clear understanding of the Cambodian context.

This objective will be accomplished through a comprehensive review of primary and

secondary literature of existing arsenic mitigation projects as well as a critical evaluation of

the appropriateness of each project for the context of Cambodia. To compliment this,

interviews may also be conducted to gain more insight and depth into the benefits and

limitations of the projects.

This research paper is being written to assess suitable water filtration systems across

Cambodia to treat arsenic contamination in groundwater.

1.5 Significance of Research

Given the discovery of the harmful health effects associated with prolonged periods of

arsenic consumption, it is necessary to take immediate action to remove arsenic in drinking

water. Studies have illustrated that an alarming number of locals in Cambodian living in

arsenic-affected communities have contracted health problems such as skin lesions, skin

cancer and internal cancers. Thus, the Cambodian population will greatly benefit from the

implementation of a water filtration system designed to remove arsenic as well as

pathogens. This research serves to provide basic knowledge on successful existing arsenic

mitigation technologies and therefore allow designers to make more informed decisions in

the design of a water filtration system to remove arsenic.

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2 LITERATURE REVIEW

After establishing the correlation between long-term consumption of arsenic in drinking water

and health issues in Bangladesh over two decades ago, emphasis has been placed on the

removal of arsenic in water filtration design. There is ongoing investigation on arsenic

contamination in groundwater across the world. In particular, it has been found that arsenic

contamination is a major issue in Cambodia, affecting over 2.25 million rural dwellers across

seven provinces along the Mekong and Tonlé Sap river banks.

This section provides a literature review containing background information relevant to the

removal of arsenic from drinking water in Cambodia. The literature review aims to facilitate a

wholesome understanding of arsenic contamination in drinking water and the Cambodian

context in relation to arsenic-affected drinking water. The literature review begins with an

investigation of arsenic contamination in drinking water by exploring the sources, behaviour

and distribution of arsenic as well as health effects of long-term consumption of arsenic. The

section concludes with background information on Cambodia including a description of

arsenic-affected areas, primary sources and usages of water as well as the societal scenario

and economic constraints. Section 3 to 4 will explore existing water treatment solutions in

Cambodia and integrate a critical analysis of the suitability of each system for treating

arsenic affected water in Cambodia.

2.1 Arsenic Contamination in Groundwater

2.1.1 Sources and Behaviour of Arsenic in Natural Waters

In some areas of the world, sources of drinking water are contaminated with arsenic, posing

significant health problems after long term consumption. It is typically found that arsenic

concentrations in groundwater are considerably higher than that of surface water, commonly

exceeding 50 mg/L while surface waters are frequently less than 1 mg/L (Smedley, 2002).

Numerous studies have been conducted to determine the cause for this difference. Studies

have revealed that there is a strong correlation between topographic environmental variables

and the content of arsenic in groundwater. These large-scale naturally occurring arsenic

groundwater problem areas tend to be found in two types of environment including inland or

closed basins in arid or semi-arid areas and strongly reducing aquifers often derived from

alluvium. In each of these environments, the groundwater flow is slow where the ground

consists of young sediments. Such environments are usually poorly flushed aquifers and

therefore arsenic released from the sediments builds up in groundwater. The groundwater is

pumped to the surface by wells and consumed by the local population (for long periods).

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2.1.2 Health Effects of Arsenic Consumption

Typically, the harmful health effects associated with arsenic consumption occur when

concentrations exceeding 50 μg per litre of water are consumed over prolonged periods. The

effects of arsenic consumption occur over time and no immediate harm is caused.

One of the most common effects of long-term arsenic consumption is the development of

skin lesions. In 1987, K.C. Saha, (Department of Dermatology, School of Tropical Medicine

in Calcutta, India) determined that of his patients from West Bengal whose primary source of

drinking water was contaminated with arsenic had symptoms of skin lesions in their upper

chest, arms and legs as well as keratoses of the palms of the hand and soles of feet.

A study of a large population in Taiwan found a clear dose-response relationship between

arsenic concentrations in drinking-water and the prevalence of skin cancer. In this study, the

average concentration of arsenic in water was about 500 mg/L and by age 60 more than

10% had developed skin cancer (Tseng WP et al, 1968).

Arsenic contamination has also caused life threatening internal cancers. Studies in Northern

Chile revealed that 5-10% of deaths over the age of 30 were a result of arsenic-caused

internal cancers of the bladder and lung. The study revealed that exposure to arsenic

reached 500 mg/L over a 10-20 year period (Smith AH et al, 1998). Similar conclusions have

been identified in Taiwan and Argentina (Hopenhayn-Rich C et al, 1996).

Other health effects associated to prolonged arsenic consumption have been discovered

and include neurological effects, hypertension and cardiovascular disease, pulmonary

disease, peripheral vascular disease and diabetes mellitus (A. H. Smith et al, 2000).

2.1.3 Distribution of Arsenic on a Global Context

Figure 1 illustrates the world distribution of arsenic contamination in groundwater, having

concentrations of more than 50 µg per litre of water. (Smedley, 2002). The most noteworthy

occurrences are in parts of Argentina, Bangladesh, Chile, China, Hungary, India (West

Bengal), Mexico, Taiwan, Vietnam, Cambodia and the USA. This paper will focus only on

arsenic contamination in Cambodia.

The following subsection provides background information on the water sources used by

locals in Cambodia and the areas affected by arsenic contamination. The aim is to facilitate

a better understanding of the Cambodian context so that several designs can be evaluated

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on the basis of what is practicable, socially and economically acceptable and complies with

regulations. The section begins by describing the prevalence of arsenic in Cambodia and is

followed by an overview of the significance of groundwater sources in Cambodia. Data

concerning the average household consumption rate is then provided. The section

concludes with the current Cambodian social and economic scenario.

Figure 1: Arsenic Contaminated Aquifers across the World

2.2 Cambodian Context

2.2.1 Arsenic in Cambodia

Several studies have been conducted to identify the areas in Cambodia where groundwater

is most affected by arsenic contamination. A trend can be observed that elevated arsenic

levels in groundwater are clustered along the Bassac and Mekong river banks and the

alluvium braided by these rivers (Goldschmidt, 2004). In addition, the provinces that are

mostly adversely affected are the Kandal, Prey Veng and Kampong Cham provinces which

are located in the south-east part of Cambodia. Concentrations have been reported to be as

high as 1,300 μg/L, far exceeding the 50 μg/L standard (MIME, 2004). Figure 2 shows the

distribution of arsenic concentration throughout south-east Cambodia.

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2 LITERATURE REVIEW

Figure 2: Distribution of Arsenic in Groundwater throughout South-East Cambodia

Figure 3: Percentage of Water Supply retrieved from Tube Wells by Province in Cambodia

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2 LITERATURE REVIEW

To further exacerbate the issue of arsenic contamination in groundwater, a significant

concentration of tube wells in Cambodia are relied upon during the dry season by south-

eastern provinces such as the Kandal, Kampong Cham and Prey Veng provinces shown in

Figure 3. The figure shows the proportion of water that is retrieved from tube wells during the

dry season.

It can therefore be seen that in south-east Cambodia, groundwater is relied upon as the

primary drinking water supply while at the same time also demonstrating arsenic

concentrations well above safe drinking water standards. The design of an arsenic filter

would therefore be critical for locations such as the Kandal, Kampong Cham and Prey Veng

provinces.

2.2.2 Water Sources

A survey conducted in 2007 by the United Nations Children’s Fund (UNICEF) and the Water

and Sanitation Program has shown that of the people participating in the survey, the primary

source of water in Cambodia is surface water during monsoonal season. The Mekong River

and the Tonle Sap Lake are the predominant sources of surface water. However, as rivers

drain and the dry season arrives, surface water and groundwater usage approximately

equal. The survey has shown that groundwater is the second most critical source of drinking

water at 44%, just behind surface water at 46% during the dry season (UNICEF and Water

and Sanitation Program, 2007). The column chart below (Figure 4) summarises the results

of the survey conducted by UNICEF and the Water and Sanitation Program. The chart

describes the primary source of water supply for households in Cambodia in the dry season.

Figure 4: Primary Source of Water Supply for Households in Cambodia during the Dry Season (Source:

UNICEF and Water and Sanitation Program, 2007)

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In addition to these findings, it is important to recognise that approximately 81% of

Cambodia is rural and of this group, many rely solely upon groundwater because of the lack

of access to surface water or shortage of surface water during the dry season. Close to 60%

of rural dwellers use groundwater as their primary source of water supply (Ministry of Rural

Development Department of Rural Water Supply, 2002). Moreover, only 15% of urban

dwellers consume groundwater.

Hence, the significance of groundwater in Cambodia along with the persistence of arsenic in

groundwater throughout the country justifies the need for the research and design of a water

filtration system.

2.2.3 Water Usage

In the case of water usage, Rural Development International Cambodia (RDIC) has found

that on average, one Cambodian will use 35 litres of water per day (RDIC, 2008). Of this

amount, 2 to 3 litres is used for drinking and the remaining amount for cleaning, livestock

and other household activities (RDIC, 2008). An average household in Cambodia contains 5

people (UNICEF, 2007) and thus household usage per day is approximately 175 litres per

day.

2.2.4 Quality of Groundwater Sources

Approximately 1607 villages located in seven provinces with a total population of 2.25 million

in Cambodia are affected by arsenic in groundwater. All seven provinces are located along

the Mekong River Basin and Tonle Sap Basin. Moreover, 38% of tube‐wells in these seven

provinces are contaminated with arsenic above (50 ppb). Since the main source of water

among these areas is groundwater, the water quality concerns that will be investigated is the

natural occurrence of arsenic. It is important to note that the quality of surface waters in

which waterborne diseases occur will not be investigated in this report as surface waters are

not the main source of water in arsenic affected areas.

Extensive field testing has been undertaken by the World Health Organisation (WHO), RDIC

and UNICEF to quantify the extent of the problem.

The WHO guideline for arsenic is less than 10 ppb (parts per billion) with the Cambodian

health standard being 50ppb. The WHO found that 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).

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Tests for the KienSvay and Takhmau districts of Kandal Province found arsenic

contamination to be so high in primary testing that secondary testing was required. 70% of

secondary samples exceeded the WHO guideline of 10ppb (WHO, 2007). Concentrations

exceed 504 μg/L and averaged over 130 μg/L.

Table 1 illustrates the composition of groundwater and the associated concentrations for the

Mekong delta region in Cambodia. The table illustrates the significant levels of arsenic in the

groundwater.

Table 1: Composition of Groundwater in the Mekong Delta in Cambodia (Hug. J.S. et al)

Groundwater Composition Mekong Delta Cambodia

pHinitial 6.9 ± 0.4

HCO3– (mM) 5.5 ± 2.5

Ca (mM) 1.1 ± 0.9

Mg (mM) 1.0 ± 0.9

Si (mg/L) 20 ± 7

Fe (mg/L) 2.2 ± 3.3

P (mg/L) 0.5 ± 0.7

As (µg/L) 150 ± 276

As > 50 (µg/L) 40%

As > 10 (µg/L) 49%

Mn (mg/L) 0.7 ± 0.7

NH4–N (mg/L) 4.9 ± 9.1

2.2.5 Safe Drinking Water Guidelines

It is mandatory that the design of all water treatment systems in Cambodia comply with the

Drinking Water Quality Standards (DWS) (MIME, 2004). DWS aims to ensure safe drinking

water to all Cambodians and that there is no associated health risks to the public. The

standards state that drinking water should be safe, clean and clear with pleasant taste and

odour. The safety of drinking water has been determined by microbiological, physical and

chemical quality where the water does not contain suspended matter, harmful chemical

substances or pathogens while the quality of drinking water has been assessed by aesthetic

factors accepted by the public. The DWS describes parameters and their associated

maximum concentration values that the filtered water must not exceed for safe drinking

water in Cambodia. These parameters and maximum concentrations are described by the

Ministry of Industry, Mines and Energy (MIME) as well as the World Health Organisation

(WHO). Note the standards should serve as the basis for the design and planning of the

arsenic filtration system.

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2.2.6 Societal Scenario

Multiple field studies have been conducted to assess the behaviour and cultural values of

Cambodians in regards to water consumption. The results of these studies should be used in

the design process of the sand filter to ensure a socially acceptable solution is met.

One such study determined that Cambodians opt to drink water that meets their aesthetic

expectations as well as expectation for odour and taste (RDIC, 2008). This claimed is

supported by another study, which indicated that surface water was preferred over

groundwater sources (Feldman et al, 2007) accounting for 46% of water use in Cambodia

(UNICEF, 2008). The study attributed the lower turbidity as well as cleaner taste and odour

of surface water over groundwater to be the primary reasons that Cambodians preferred not

to drink groundwater (Feldman et al, 2007).

Groundwater sources often contain high levels of naturally occurring minerals that

Cambodian’s feel are unpleasant to drink or use. The most common dissolved minerals

affecting the aesthetic properties of groundwater in Cambodia include iron, manganese,

sodium chloride and hardness (calcium and magnesium) (Feldman et al, 2007). Cases of

high levels of iron and manganese have caused unfavoured taste and odour of the water,

stained clothes when washed in the water and corroded pipes and metal fittings while

calcium and magnesium caused bitter-tasting water and scale deposits in cooking pots

(Feldman et al, 2007). Elevated levels of these minerals have caused consumers to reject

newly installed water supplies in the past (Feldman et al, 2007).

Since dissolved arsenic in water is virtually undetectable as it is odourless and tasteless and

that health problems are only noticeable after decades of consumption, there is an

understandable ignorance in regard to arsenic contaminated water. RDIC concluded that

Cambodian’s are aware of the health issues associated with consuming arsenic

contaminated water but have not acted on this. Moreover, it is a widely accepted belief that

clear water is safe in Cambodia (RDIC, 2008).

Cambodia's poor health standards are exacerbated by a lack of basic health education and

income. In Cambodian culture, the importance of safe hygiene and sanitation are

undervalued which therefore limits the possibility achieving improved health outcomes in

drinking water (WHO, 2004).

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2.2.7 Economic Constraints

The continual advancement of technology has seen a variety of water treatment methods

that can produce virtually any desired quality of water from any given source; the limiting

factor being economic rather than technical. For example, water can be obtained from highly

contaminated sources such as seawater or sewage effluent and treated using methods such

distillation, electrodialysis or reverse osmosis to produce extremely high degree of purity,

however the capital and running costs associated with these water treatment methods are

very expensive. In developing countries such as Cambodia, this is impractical. This section

provides data on the average income of rural communities and an overview of the

Cambodian economy. Consequently, design (such as material selection) and

implementation will be restricted to costs affordable for communities in Cambodia.

With a steadily increasing population of 15.4 million people, the Cambodian economy has

also continued to strengthen significantly, seeing high amounts of growth in the agricultural

and tourism industry. In 2013, the Cambodia GDP grew at a rate of 7.0% and was valued at

$39.7 billion (IEF, 2014). In addition, 0.3% of the population are unemployed (IEF, 2014).

Despite these promising statistics, further research revealed many Cambodian’s are still

facing poverty and that a community scale filter may better suit the economic scenario of

Cambodia. Community scale filters are classified as public goods and will allow users free

usage of the filtering system.

It is anticipated that the implementation of a community scale water filter will result in positive

effects to the Cambodia economy. The project will require initial funds for construction to be

sourced by external aid agencies supporting regional or large scale clean drinking water

projects. Hence, this will provide an autonomous injection of investment into the economy. In

addition, since the filter is of a communal or household size, it is appropriate that local

tradespeople will be responsible for the construction and erection of the filter. This will

increase employment opportunities and domestic expenditure for locals in Cambodia.

2.3 Factors to Consider in Water Filtration Design

To be successful, the mitigation strategy must take into account the geological differences in

groundwater; the economic resources of the population; the availability of infrastructure for

water treatment and the acceptability by the community (Hug S.J. et al). Other

considerations include ease of implementation, installation, maintenance and use;

performance; waste removal; limitations; and overall impact to the community.

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The literature review briefly touched upon the vast majority of locals in Cambodia living along

the Mekong delta floodplain and Tonle Sap River who are dependent on groundwater

sources. In addition to this, the literature discussed the occurrence of high concentrations of

arsenic in groundwater and that the locals living in these lowland alluvial areas are at high

risk of arsenic poisoning and the associated health effects. As such, schemes have been

implemented across the world endeavouring to remove arsenic from drinking water.

This section describes several techniques that can be implemented for a filter design for the

removal of arsenic in water. Several existing projects that utilise these techniques have also

been described to show their practical applications. Finally, each existing project listed is

neatly summarised in a table. The table provides an overview of the projects against set

criteria (e.g. % of arsenic removed, capital costs etc) and is intended to assist the designer

in applying the appropriate technology to their situation. Educated recommendations on the

technologies used to remove arsenic are then provided for the remainder of the paper.

3.1 Arsenic Removal Techniques

Through the means of laboratory and field testing, there are many techniques that have

been proven to remove arsenic from water. These arsenic removal techniques include

oxidation; adsorption (sorptive filtration); coagulation and filtration; and membrane

techniques. A brief description of each technique has been given below.

(1) Oxidation and Sedimentation

Arsenic removal technologies most effectively remove arsenic in its pentavalent form,

arsenate (As(V)) as it is less mobile than the trivalent form, arsenite (As(III)). This is because

arsenate tends to co-precipitate out with metallic cations or adsorbs onto solid surfaces. As a

result of this, many arsenic removal treatment systems often involve converting arsenite to

arsenate as the first point of action.

In order make this conversion, an oxidation process is required to take place. There are

many oxidising agents that allows for the conversion and include oxygen (most common),

hypochlorite, permanganate and hydrogen peroxide.

Oxidation with oxygen existing naturally in the air will reduce arsenic concentration in stored

water. Oxidation by oxygen is also known as passive sedimentation. For passive

sedimentation, the water needs to be stored for a sufficiently long time allowing the

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exchange of oxygen from the air to the water and is considered to be a very slow process

(Pierce & Moore, 1982).

(2) Adsorption (Sorptive Filtration)

Existing research has reported the success of several sorptive media in removing arsenic

from water. These sorptive medium include activated alumina, hydrated ferric oxide, hydrous

cerium oxide, activated carbon, iron coated sand, kaolinite clay, activated bauxite, titanium

oxide, silicium oxide and many natural and synthetic media.

The process of adsorption involves placing a packed column of sorptive media into the raw

water. Once immersed, the impurities including arsenic present in the water are adsorbed on

the surfaces of the sorptive media grains. Note that larger the surface area (m2/g) of the

sorptive media, the more effective the adsorption process will be. When the packed column

is saturated and can no longer filter impurities from the water, the sorptive media must be

recharged or replaced. A specified chemical is usually required to recharge the saturated

sorptive media. The recharging or replacement process is quite expensive and would not be

suitable for rural dwellers in developing countries. The process also leaves sludge and is not

a sustainable solution in the long-term.

Examples of sorptive medium used in existing projects to remove arsenic have been outlined

in Section 3.3 and brief descriptions on the process and their success rate have been given.

(3) Coagulation and Filtration

Coagulation technology is an effective technology for the removal of arsenic in water. The

most common methods of coagulation for the removal of arsenic from water are with metal

salts and lime. At present, it is possible to reduce arsenic from 400 μg/L to 10 μg/L at a rate

of 500 L/sec, assuming variables including pH, oxidising and coagulation agents are

controlled (Sancha, 2006). However, it has been reported that the arsenic removal by lime is

relatively low, between 40–70%.

The process of coagulation involves adding the coagulated substance into the raw water and

stirring the water until the substance dissolves. Thereafter, the flocculation process takes

place where all kinds of micro-particles and negatively charged ions are attached to the flocs

by electrostatic attachment. Arsenic is also adsorbed onto the coagulated flocs. The flocs

are then removed partially by sedimentation, followed by filtration to ensure complete

removal of all flocs.

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3 ARSENIC MITIGATION OPTIONS

(4) Membrane Techniques

Membrane techniques are capable of eliminating many contaminants from water including

dissolved arsenic. There are three membrane techniques that are capable of eliminating

arsenic from water including reverse osmosis, nano-filtration and electrodialysis.

The process of using membrane techniques involves raw water passing through special

selective membrane which physically retains the impurities present in the water (Ahmed F.

2011). The membrane has microscopic pores that are specially sized to allow water

molecules through, while trapping larger inorganic molecules like lead, iron, chromium,

manganese and arsenic.

The technique requires very little maintenance and no addition of chemicals. However, using

membrane techniques at household level provides little amounts of purified water while at

community level, it becomes very expensive to operate and maintain. The technique may

cause the water to taste bland due to the inorganic materials removed in the treatment

process.

3.2 Existing Projects in Cambodia

To demonstrate the practical applications on the techniques in the previous section, several

existing projects are described herein. This will aid in discerning the technique that would be

most suitable for removing arsenic in drinking water in Cambodia.

Kanchan Arsenic Filter (KAF) [adsorption techniques]

Based on 7 years of extensive laboratory and field studies in rural villages of Nepal,

researchers at the Massachusetts Institute of Technology (MIT), Environment and Public

Health Organisation (ENPHO) and Rural Water Supply and Sanitation Support Program

(RWSSSP) have developed the Kanchan Arsenic Filter (KAF), a system to remove arsenic

from drinking water in addition to providing microbiological water treatment (Ngai et al 2006).

The KAF is a household water treatment device that has been adapted from the Bio-Sand

Filter (BSF) and involves slow sand filtration and iron hydroxide adsorption techniques.

Pathogen removal involves standard sand filtration techniques while arsenic removal is

achieved by incorporating a layer of non-galvanised nails in the diffuser basin of the filter

where the arsenic adsorbs on the rusted iron nails surface and is removed from the water.

Figure 5 illustrates the cross-section of a typical Kanchan Arsenic Filter.

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3 ARSENIC MITIGATION OPTIONS

Figure 5: Cross-section of Kanchan Arsenic Filter

illustrating the Components

The KAF was tested under two conditions;

the first being under laboratory study in

Cambodia in 2006 by the Institute of

Technology of Cambodia (ITC) and then an 8

month field technical pilot demonstration

project in rural Cambodian communities.

The results demonstrated that the system

was successful as the KAF consistently

removed over 95-97% of arsenic, total

coliforms and E.coli from arsenic

contaminated groundwater. In other words,

the filters reduced arsenic levels from an

average of 637ppb to less than 50ppb.

These successful results allow for a reliable

mitigation option to arsenic affected households. In considering maintenance tasks, the KAF

does not require external energy or material input for operation and replacement parts with

the exception of iron nails (Chea S. et al, 2008). In addition, since the KAF uses biological

material such as sand, it is relatively cheap. Using the KAF results in arsenic-liquid-waste

formation and requires a high standard of waste management for safe disposal.

Subterranean Arsenic Removal (SAR) [oxidation techniques]

Developed by Professor Bhaskar Sen Gupta and his team of scientists in Queen’s

University, the Subterranean Arsenic Removal (SAR) Technology is a simple and easily

adaptable technology that removes arsenic from groundwater using controlled oxidation.

At present, there are nine SAR plants implemented across India, Cambodia and Malaysia

with more than 13,000 people receiving SAR treated water supply. Of the communities using

SAR Technology, significant signs of recovery from arsenic poisoning have been observed.

In a modified in situ process, water is oxidised above-ground and injected back into the

aquifer, where ferric arsenate particles are then filtered (Sengupta B. et al, 2008). Error!

Reference source not found. illustrates the process taken by SAR Technology.

The results obtained during testing in West Bengal, India illustrated that the arsenic and iron

concentration gradually dropped to a permissible limit (below 0.01 µg/L (WHO guideline))

from an initial very high concentration of 250 µg/L within 45-50 days of operation.

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Figure 6: Diagrammatical Representation of the Process

taken by SAR Technology

The greatest advantage of using SAR Technology is that the filtration process is chemical

free and results in no sludge. As a result, the process not only saves on disposal costs but is

also eco-friendly. The technology

is simple, easy to handle and is

very cost effective (low capital

and operational costs) and hence

SAR is suitable for developing

countries. In addition, the system

also has no restriction on the

volume it can handle.

The only disadvantage is that

SAR takes time to stabilise

because of the slow kinetics of

the oxidation process since the

oxygen rich impregnated

water requires time to create

the adequate oxidising zone

in the deep aquifer. Another consideration is that uncalculated amount of oxidation of the

aquifer can reverse the system resulting in arsenic and iron precipitation rather than

adsorption.

3.3 Projects Outside of Cambodia

Akin to subsection 3.2, this subsection serves to demonstrate the practical applications of

the techniques in relation to projects outside of Cambodia. Note projects that exclusively use

oxidation techniques have not been discussed because arsenic more effectively mitigated

from water in its pentavalent form (arsenate) which requires oxidation as the first point of

action, hence oxidation is discussed in combination with other techniques. This is Note also

that only brief descriptions will be provided for each project and the interested reader is

encouraged to seek further information by referring to the sources indicated.

(1) Adsorption (Sorptive Filtration)

Activated Alumina

Activated alumina can remove arsenic from water and is found to be highly effective as it has

a large sorptive surface and. A packed column of activated alumina is immersed into the

17

3 ARSENIC MITIGATION OPTIONS

contaminated where the impurities including arsenic in the water are adsorbed on the

surfaces of the media. As the column becomes saturated, regeneration through the use of

caustic soda of the saturated alumina is required.

Examples of activated alumina include the Bangladesh University of Engineering and

Technology (BUET) Activated Alumina, Alcan Enhanced Activated Alumina, Arsenic

Removal Units (ARU) of Project Earth Industries Inc, USA and Apyron Arsenic Treatment

Unit. The technologies were found to average an arsenic reduction concentration of less

than 10µg/L.

Read-F Arsenic Removal Unit

Produced by Shin Nihon Salt Co. Ltd in Japan, Read-F is an adsorbent for arsenic removal

in Bangladesh. Read-F is made from ethylene-vinyl alcohol copolymer-borne hydrous cerium

oxide and hydrous cerium oxide is the adsorbent. The product is not classified as hazardous.

Laboratory test at BUET and field testing showed the product is highly sensitive to arsenic

ions under a broad range of conditions and effectively adsorbs both arsenite and arsenate

without the need for pre-treatment. That is, the adsorbent is highly effective in removing

arsenic from groundwater (SNSCL, 2000).

Iron Coated Sand

Iron coated sand is effective in removing both arsenite and arsenate. The preparation of iron

coated sand can be found in a study by (Ahmed, 2011). Field tests in Bangladesh showed

that raw water having 300 µg/L of arsenic when filtered through iron coated sand resulted in

arsenic free water.

The Shapla Filter is an example of an arsenic removal technology using iron coated sand

adsorption processes. As water passes through the filter, the arsenic present in the water is

absorbed to the iron coated sand. The filter can remove arsenic to virtually untraceable

levels. The filter operates at a household level and can hold up to 30 litres of water. The filter

can provide average of 25 to 32 litres of safe water to households per day.

Indigenous Filters

Sorptive media developed using indigenous Bangladesh material such as red soil rich in

oxidised iron, clay minerals, iron ore, iron scrap or fillings and processed cellulose materials

are known to have capacity for arsenic adsorption.

18

3 ARSENIC MITIGATION OPTIONS

Examples of filters using these materials include Sono 3-Kolshi Filter, Garnet Home-made

Filter, Chari Filter, Adarsha Filter, Shafi Filter and Bijoypur Clay/Processed Cellulose Filter.

Arsenic can be removed by up to 97 % using these sorptive media.

Since the above mentioned adsorption techniques have not been investigated in

detail, they have not been included in the summary evaluation in this paper. These

techniques have been listed as they could potentially provide an effective solution depending

on the scenario. The interested reader is encouraged to further investigate these techniques.

(2) Coagulation and Filtration

The following examples of coagulation and filtration arsenic removal technologies have been

proposed by DPHE-Danida in Bangladesh and include the Bucket Treatment Unit, Stevens

Institute Technology, Fill and Draw Units and Arsenic Removal Attached to Tubewell.

Bucket Treatment Unit (BTU)

The Bucket Treatment Unit (BTU) removes arsenic from water by using a combination of

oxidation as well as coagulation and filtration processes. BTU is limited to household level

use only. The system works by the use of two plastic buckets, each 20 litres, placed one

above the other. In the upper bucket, chemicals are mixed with the polluted water by hand.

The chemical used includes aluminium, sulphate and potassium permanganate and are

supplied in powder form. Through a plastic pipe and sand filter box, the water in the upper

bucket flows through to the lower bucket. This technique has found cases with higher than

safe levels of aluminum and manganese.

Stevens Institute Technology

This technology also uses two buckets lying side by side. The first bucket mixes chemicals

including iron sulphate and calcium hypochloride which are supplied with the polluted water

while the second bucket serves to separate the flocs by sedimentation and filtration. Field

study illustrated that the Stevens Institute Technology reduced arsenic levels to less than

0.05 mg/L for 80% to 95% of the samples tested (BAMWSP, DFID, WaterAid, 2001). The

problems associated with the technology include quick clogging by floc in the sand bed and

requires washing at least twice a week.

Arsenic Removal Unit Attached to Tubewell

The Arsenic Removal Unit Attached to Tubewell project uses coagulation, sedimentation and

filtration techniques to treat the polluted water. The project has been implemented in villages

19

3 ARSENIC MITIGATION OPTIONS

in West Bengal, India. The project demonstrated a 90% effective arsenic removal from

tubewell water having initial arsenic concentration of 300μg/L. More information about this

project can be found in a study by (Ahmed, 2011).

(3) Membrane Techniques

MRT-1000

A household level reverse osmosis water dispenser named MRT-1000 was promoted in

Bangladesh by Jago Corporation Limited. This system was tested at BUET showing an

As(V) removal efficiency of more than 80%. Experimental results also showed that the

system could reduce other impurities in water effectively.

Reid System Limited

A larger scale reverse osmosis system named Reid System Limited was also implemented

in Bangladesh and showed similar results to MRT-1000. The capital and operational costs of

the system however are much higher due to the larger size.

3.4 Summary of Existing Arsenic Mitigation Projects

This section provides a comparison between of the arsenic filtration techniques and projects

that implement them. The comparison is based on criteria that enable the reader to assess

which design would be most appropriate for any other potential project. Table 2 describes

the criteria that were used to evaluate each of the filter designs so that they could be

compared directly. Table 3 provides an evaluation of the filter design listed in this research

paper.

Table 2: Criteria used to Evaluate Filter Design

Design Attribute Criteria

Technique Which technique does the filter use including oxidation; adsorption; coagulation;

or membrane techniques?

Functionality Is the filter able to remove arsenic?

Is able to provide safe drinking water?

Cost

Capital Cost

Implementation and installation cost

Operating and maintenance cost

Resources Requires skilled trades people to install and/or maintain

Performance

Percentage of arsenic removed from water

Percentage of other contaminants removed from water

Time required to filter water until safe for consumption

Size Individual/Household/Community/Commercial

Waste Removal Requires waste removal

20

3 ARSENIC MITIGATION OPTIONS

Table 3: Comparison of Existing Arsenic Mitigation Technologies listed in Research Paper

Arsenic Mitigation

Project

Arsenic Mitigation Technique

Oxidation; Adsorption; Coagulation; Membrane

Techniques

Functionality

Safely removes arsenic and

contaminants

Cost (in AUD$)

Capital cost; Operating and maintenance costs

Performance

Removal efficiency; Time efficiency

Size

Household or Community

Waste Removal

Yes/No

Kanchan Arsenic Filter (KAF)

Adsorption Yes

Capital Costs: $40 to $50 per person depending on location

No operating costs (except replacement of nails)

95% – 97% arsenic removal efficiency and 60% – 100% total coliform and E.Coli removal

Initially, just after filter installation, the flow rate can be as high as 30 L/hr. The flow rate will drop over time, to about 15 –20 L/hr in a month or two.

Household Yes

Subterranean Arsenic Removal

(SAR) Technology

Oxidisation Yes Not cost effective for developing countries

99.9% arsenic removal efficiency

45 – 50 days of operation Community No

Bucket Treatment

Technology (BTU)

Coagulation Yes Capital Costs: $10 to $15 Removes arsenic to below 50 µg/L

About 5 litres of water per capita per day Household Yes

Stevens Institute Technology

Coagulation Yes Capital Costs: $5 per family Arsenic concentration in drinking water was

reduced from 600 µg/L to less than 50 µg/L Household Yes

Arsenic Removal Unit Attached to

Tubewell Coagulation Yes Unavailable data 90% arsenic removal efficiency from tubewell

containing 300 µg/L of arsenic in water Community Yes

MRT-1000 Membrane Technique

(Reverse Osmosis) Yes

High capital and operational costs and not suitable or developing countries

80% arsenic removal efficiency Household Yes

Reid System Limited

Membrane Technique (Reverse Osmosis)

Yes High capital and operational

costs and not suitable or developing countries

80% arsenic removal efficiency Community Yes

21

4 RECOMMENDATIONS

In light of the previous, this chapter will provide recommendations for potential future

pathways for design work, as no formal design work was conducted. Note that many details

are subject to change throughout the project’s life cycle. The work remaining in this project

involves the design of a water filter for provinces in Cambodian such as the Kandal, Prey

Veng and Kampong Cham provinces.

Although many different water filtration systems were described, it is recommended that a

household or community scale water filter is used, given the economic limitations of the

affected Cambodian provinces. A community scale would allow for an affordable means for

providing safe drinking water to a large number of people while household filters allow for the

dismissal of skilled labourers during construction, operation and maintenance and provide

safe drinking water for families.

For these reasons, the Kanchan Arsenic Filter system may be a suitable option, as it is

affordable and easily operated without excessive maintenance costs. More specifically, the

KAF is a household filter that is able to provide essentially arsenic and microbiological-agent

free water (95-97% removal efficiency for arsenic) and meet social acceptance as the filtered

water is free from unpleasant odour, taste and turbidity. Resources including materials and

skilled labour are available locally, that is, there is no need for external aid of obtaining

materials or construction. In addition, the filter is very simple to use and does not require any

training. There is however a waste removal requirement.

Future design work must also conduct detailed requirements analysis for these provinces,

which may require field testing and collecting samples of drinking water. This would provide

a solution for overcoming arsenic contamination that is specific to the provinces that the filter

is to be designed for.

Finally, to ensure acceptability of the water filter design, it is recommended that locals in

Cambodia are surveyed and educated on the use and benefits of the filter. Doing so will

allow the operation and maintenance of the filter without constant aid from external entities.

22

5 CONCLUSIONS

This report has presented a comprehensive review of primary and secondary literature for a

project to provide safe drinking water to locals in small communities located in Cambodia.

More specifically, the aim of the project is to design a water filter to remove contaminants,

and in particular arsenic, from the drinking water sources in order to prevent adverse health

conditions such waterborne diseases and skin cancer.

A literature review was presented that highlighted the areas in Cambodia most adversely

affected by arsenic contamination, which included the Kandal, Prey Veng and Kampong

Cham provinces in south east Cambodia. Existing literature determined that the main source

of drinking water for these provinces is groundwater and that these groundwater sources

contained very high levels of arsenic concentration deemed unsafe for drinking (RDIC, 2008;

WHO, 2004; UNICEF, 2008).

The paper then proposed that a design for a water filter should be investigated in order to

provide such areas in Cambodia with safe drinking water. Several existing water filtration

techniques for arsenic removal were described. Existing projects that have implemented

these techniques were also described to illustrate practical applications of the techniques.

The investigation into the existing projects serves to stimulate further research into suitable

technology to remove arsenic from water in Cambodia and provide base knowledge for

future design work.

With key considerations in mind including the functionality of the filter, economic resources

of the population; the availability of infrastructure for water treatment and the acceptability by

the community as well as an all-encompassing review of the Cambodian context, two

selected technologies have been recommended. It has been recommended that the design

of the water filter should be based on the processes and techniques applied to the Kanchan

Arsenic Filter or the Subterranean Arsenic Removal Technology.

23

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28

About the Author

My name is Molis O’nilia

Nou but most people call

me Mel! I am in my final

year studying to

complete my Civil

Engineering degree at

the University of Sydney.

I have a strong passion

for humanitarian

engineering and as a

result, I became involved

with Engineers Without

mm Borders (EWB) Australia at the University level joining the Usyd

Chapter. I participated in the High School Outreach Program and

Appropriate Technologies Program. Shortly after, I became the

Secretary and Communications Coordinator for the NSW region.

As an avid supporter of humanitarian engineering, I sought to

participate in another initiative by EWB and was assigned to a

research project soon after. This paper is a product of the research

project deliverables. My involvement in this research project is of

particular significance to me as the project seeks to improve the

development of Cambodia as a nation. As Cambodia is the country

where my ancestors orgiinated, I have a deeply rooted personal

connection with the country. In addition, having been indirectly

affected by the Khmer Rouge, I have always wanted to create a

positive change in Cambodia.