Submitted to Journal of Health Population and Nutrition
Revision October 14th 2005
ONE SOLUTION TO THE ARSENIC PROBLEM:
A RETURN TO SURFACE (IMPROVED DUG) WELLS
Sakila Af. Joya, Bivash C. Barmon, Ariful Islam, Golam Mostofa, Altab Elahi, Jabed Yousuf ,
Golam Mahiuddin#, Mahmuder Rahman, Quazi Quamruzzaman
Dhaka Community Hospital
Wireless Railgate
Dhaka, Bangladesh
Richard Wilson
Department of Physics*
Harvard University
Cambridge, MA 02138, USA

Address to whom correspondence should be addressed
# Address to whom requests for reprints should be sent
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Abstract
The problem of contamination of drinking water in Bangladesh by arsenic is a major
catastrophe that dwarfs most other man made disasters. The national policy is to encourage a
return to the plentiful surface waters in so far as possible without encountering the problems of
sanitation that led to the use of ground water in the first place. In this paper we describe the
procedure and the success of the Dhaka Community Hospital team in implementing sanitary,
arsenic free, dug wells. The capital cost per person for running water is between $5 and $6 per
person. Since it seems that other groups have not had the same success, we include a detailed
description of the recommended procedures that others may follow in appendix 1. A detailed
cost breakdown is provided in appendix 2 and a description of the initial chemical and
bacteriological measurements is in appendix 3.
Key words: arsenic, dugwells, sanitary, coliform,
Introduction
The arsenic problem in Bangladesh has been widely discussed . About 20-40 years ago
people in Bangladesh the past 40 to 50 years, have been abstracting ground water by sinking
tube wells . The wells were cheap. The water seemed to be free of the bacteria that had caused
cholera. This seemed to be a magic solution to the nation’s drinking water problems. But it
produced its own very serious problems. About 30% of the wells contained too much arsenic.
Physicians at Dhaka Community Hospital (DCH) became aware of the ailments caused by
arsenic as early as 1982. But world attention was not brought to bear until the first (of eight)
International Conference on arsenic held by Dhaka Community Hospital in January 1998 held
jointly (in Dhaka) with Jadavpur University, Kolkata1. At that time also, DCH and Uposhon
carried out a 500 village rapid assessment2. DCH and Jadavpur University carried out detailed
surveys in many villages3 . At that time there were several “obvious” conclusions.
(1)
(2)
(3)
(4)
A short term solution might be acceptable if it was implemented on a wide scale at once.
A long term solution should fit into a national water policy
There was no reason for delay; short term solutions should be implemented at once.
A simple return to unsanitary surface waters is undesirable
The proposals that were made at once were:
(i) to have a national survey of wells,
(ii) encourage well switching (use of a well without arsenic) and
(iii) install temporary (household scale) arsenic removal devices.
(iv) Use deep wells (deep enough to penetrate a clay layer)
However 7 years later, there was delay, the short term quickly became a long term and
there are many villages still without pure water. Well switching has been variable: some
estimates are that only 30% of villagers switched wells. Columbia University scientists find that
the number is 60% in the area they studied, perhaps because they had an intense village
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education program. Moreover it is strongly suspected that continued pumping from a safe
(green) well can bring arsenic laden water into that part of the acquifer. The arsenic removal
devices proved too hard for many villagers to use and many of them were unsatisfactory and
were abandoned4. And some scientists have cautioned against indiscriminate use of deep wells.
Although the arsenic contamination of this deep layer is at present much smaller than the arsenic
contamination of the ordinary tube wells at a depth of 40 meters it is unclear whether it will
always remain so.5 In Dhaka continuous extraction of ground water is non rechargeable at the
same rate of extraction, and has resulted in severe lowering of the ground water level.
According to the WASA report 2003 6, the ground water level that was 11m in 1970s went down
to 20m in 1980s.
In 2003 the Government of Bangladesh (GOB) promulgated a “National Water Policy”7
which gives priority to surface water use among other options. These surface water options
seem to be:
1) Encouraging a return to surface (dug) wells (DW), but with a strict adherence to WHO
sanitary standards.
2) Use of sand filters to filter pond water (PSF) or river water (RSF)
3) Storage of rain water
In all solutions, involvement of the local community seems essential. DCH is
particularly suited to such pilot projects because each of their 40 local clinics can act as a focus
for action. DCH chose the second of these surface water solutions, the use of dug wells, for this
first demonstration facility in the Pabna district. This report describes three phases of the work
starting in the year 2000, till 2003, and some indication of further developments in another
district since 2003. Further tests on some of the wells in 2004/5 are also included. Other
groups are actively studying other solutions, including use of deep wells, and we make no
premature claim on whether, or where, a particular solution will prove to be the best.
The DCH Dug well Demonstration (Pilot) Project
Dugwells have been used for time immemorial, but were replaced by tube wells because
of simplicity and in particular freedom from bacterial contamination without the apparent
necessity of careful maintenance. A return to dugwells seems, therefore, an obvious possibility.
However this has not been uniformly successful. This project was begun to demonstrate that it
is possible to have bacteria free wells if due care is taken and in particular if WHO requirements
were followed.8 While this is obvious in a temperate climate such as UK, it is far from obvious
in the tropical village conditions of Bangladesh. There were therefore several aims. Will the
wells be bacteria free? Will the wells be free of arsenic and other undesirable chemicals? What
will be the cost? What maintenance is necessary? Are there other conditions such as limited
choice of sites that are necessary to achieve these aims? Will the wells be acceptable to the
people? After the start of the project DCH noted that the Bangladesh government electrification
program had already brought electricity to 50% of all villages and has the aim of bring electricity
to them all by 2020. This makes it easy to install an electric pump to raise the water to a storage
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tank, from which it is gravity fed by pipeline to a number (6 or more) individual houses. This
has proved very popular and is a major step toward the widespread acceptability of this solution.
It is interesting that Ahmad et al.9 found by survey that the availability of running water is more
important in public perception than the fact that the water is arsenic free. The Bangladesh
Arsenic Mitigation Water Supply Project (BAMWSP) has also stated its intention of providing
30 pipeline systems10. However we have no further information about them.
Although the project was begun in late 1999, it started in full measure in April 2002. In
the first phase 39 wells were dug, (or in some cases reconditioned) by February 2003. These
wells supplied 631 families and serve 3,250 users. Only one had a pipleine system attached. In
phase 2 seventeen new wells were dug and all had the pipeline system installed. Another 518
families were supplied and 2,903 users were served. In phase 3, nine old wells were renovated
(brought up to WHO sanitary standards) and one new one dug; all with electric pump, storage
tank and pipeline. This supplied another 400 families with 2,400 users.
In all 66 sanitary dug wells were installed in this demonstration pilot project in the Pabna
region. This region was chosen for a number of reasons. Firstly, the need seemed great in this
area. In several villages all, or nearly all, tubewells showed excessive levels of arsenic. In
several villages patients with evident arsenic related lesions had been found. Secondly, DCH
has a clinic in Pabna where patients may be seen and water samples analyzed. Thirdly
epidemiological studies of arsenic lesions are being studied in this region by DCH together with
a group from Harvard University. The general geographical location of these wells is shown in
figure 1.
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DUG WELL LOCATION MAP(WILSON P
No
Procedure for the installation of a Dug Well with Pipeline
March and April, which are the driest months in the country, are the best times for
digging a well. During this period, ground water remains at the lowest level so that if the well
hits water at that time it will always hit water. We believe that it is crucial to emphasize that
DCH does not own the wells. The community owns the wells and is responsible for their
installation and maintenance. DCH merely facilitates these, and in this paper reports upon them.
Because of the crucial importance of the full participation by the community, and the fact that
this has not always been achieved, we outline the procedures DCH have adopted to ensure this
responsibility.
DCH found that there were several major distinct activities, none of which can
be omitted if success is to be assured: Community mobilization, Committee formation, Training
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of community workers and the caretaker, Site selection, Drawing of water supply network,
Installation of dug well and pipe network, Community meeting, Water quality monitoring.
These are detailed below.
Community mobilization
Various mobilization and motivational activities were conducted, such as courtyard
meetings, to increase public awareness. Several meetings with the community were held in each
village. Local Government of Bangladesh (GoB) elected persons and influential local people
were present in meetings along with the DCH personnel. Community people including women,
the poor and arsenic patients shared their situation, needs, opinions and preferences about
mitigation options with DCH and others.
Committee formation
In each village a committee was formed for the supervision of each stage in the
implementation. Each committee was responsible to maintain the option provided to them. DCH
and the committees worked together to plan option installation and maintenance. The committee
accepted responsibility to collect the community contribution. The committee decided the
charges for water use for each family. A caretaker collected money from water users (usually
20 Tk or 35 cents a month for each family). Each family was provided with a water card for
payment.
Training
Local mistris were selected for construction and maintenance of the options. They were
trained on construction work options by DCH trainers. DCH trainers also trained caretakers and
users of options.
Site selection
Sites for wells were selected in areas highly contaminated by arsenic. This was done after
consultation with the community. Preference was given to sitting the wells near the patient
families and the poor. All 66 sites satisfied guidelines provided for site selection, including but
not limited to:
- Preparing a Dug Well 30-40 ft away from the latrine and dumping ground of waste materials
- Animals are penned away from the Dug Well
- The Dug well is installed at a safe distance from cropland and industrial area etc.
A detailed check list for adequacy of the site selection is being prepared taking account of
the expereince gaines so far
Installation
A hole is dug with a diameter of about 36 inches. The depth of the well varies from place
to place. A ring of cement or baked clay is set from bottom to top and the rings are joined
(sealed) by cement to keep the well water safe from contamination from contaminated surface
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water. An apron of about four feet is made around the head wall and a 30-40 feet drain is
constructed at the ground level to avoid water seeping into the well around the head wall. An
electric pump pumps water from dug well to an overhead reservoir of 3,000 liters. This
overhead tank is installed on an iron stand, 15 feet tall. The stand is fixed on the ground with
RCC work. A main water supply pipe (made of 3 /4'' plastic) is connected with the tank for
distribution of water to the household level. A GI pipeline of ½ inch plastic is connected with
the main line to supply water to each individual household. 40-50 households are connected
with a single main supply line. To prevent accidents, during construction of Dug Well, due to
collapsing of side-soil and occasionally asphyxiation from carbon dioxide and methane gasesrope, ladder, a Bosun’s chair and other safety equipment are kept at the site. A 30-40 feet drain
is constructed at the ground level to avoid water seeping into the well around the head wall.
Water quality monitoring and the Importance of Measurements
One of the most important functions of the village committee is the continuous
monitoring and guarantee of water quality according to quality guidelines prepared by DCH in
consultation with experts and according to the WHO guide lines. In this the village committee
can call upon the advice and help of Dhaka Community Hospital and others. This aspect of the
implementation is so important, and so often neglected that we emphasize it in a separate section
here.
Failure to make adequate measurements has been at the heart of the tragedy of
Bangladesh. For 20 years no one measuremed the arsenic levels in even a small sample of the
millions of tube wells until it was too late. More recently many small-scale arsenic removal
devices were installed without adequate measurements to demonstrate their efficacy. Some
NGOs returned to surface waters without following WHO sanitary guidelines and without
measurement of possible bacteriological contamination. For this, and other, reasons DCH have
insisted on measurements from the outset. Because of the past failures in this regard, DCH
recommend that a copy of all measurements be publicly available, for it is important that not
only the individual who has the well be convinced, but also DCH as a whole and through DCH
the wider community. The measurements of this pilot project are available in appendix 3 and
more detail is available on the web at http://DCHtests.arsenic.ws.
Measurement of Arsenic Concentrations:
It is extremely unlikely that aerated surface waters will have the same level of arsenic
that the deeper wells do. One present speculation is that the arsenic is dissolved by the water
when there is an anoxic environment11 and having a well open to the air is therefore helpful.
Indeed there was no report of chronic arsenic poisoning in the thousands of years of use of
dugwells before the tubewell came into use. Dipenkar Chakraborti reports12 on measurement of
700 dugwells in Bangladesh and West Bengal and finds that 90% have levels less than 30 ppb
and only a few have 50 ppb. More recently in phase 1 of the “Risk Assessment of Arsenic
Mitigation Options (RAAMO) by the Arsenic Policy Support Unit found that 1% of dugwells
they surveyed had arsenic above 50 ppb but none with the very high levels found in ordinary
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tube wells.13 This suggests that the frequency of arsenic measurement is less important than the
measurements of coliform bacteria. The problem with the requirements for arsenic measurement
is that we are asking to reliably measure levels of arsenic at 50 parts per billion in water when
other chemicals are present at much higher levels. Laboratory instruments can, in principle,
achieve this with no difficulty by gas chromatography (with $30,000 cost for each equipment)
but this involves taking samples in the field and bringing them back for measurement. A simple
calculation performed 4 years ago showed that there was barely enough equipment in
Bangladesh to measure every well every 1000 years! Worse still, an interlaboratory comparison
by the International Atomic Energy Agency showed, in an unpublished draft report 14, frightening
disagreements. Measurements in the field are even worse. The field kits depend upon a visual
identification of the color. This depends critically upon the training of the personnel. A group of
Bangladeshi and Bengali scientists report on their comparisons in 2002 and insist that “facts and
figures demand improved environmentally friendly laboratory techniques to produce reliable
data”15 . There is hope on the horizon. More recent (2005) laboratory comparisons of water
samples with the IAEA laboratory show that several laboratories are in full agreement Some
laboratories seem to fail in the precision of the measurements. The lower precision (25%) is not
important for the present purpose. Columbia University scientists find that the Hach kit can be
reliable if used in a slightly different manner than recommended by the manufacturer 16 but this
information was not available to DCH at the time.
It is not anticipated that arsenic levels will be high in surface wells, whether tube wells or
dug wells, and it has been suggested that aerated dugwells have even less arsenic. While
measurement is important, it is less important for dugwells than the measurement of coliform
bacteria. For the measurements in appendix 3, the Silver Diethyldithiocarbamate Method was
used. It is well known that this is difficult to use below 5 ppb. Cross calibrations with
measurements at Harvard University (but not using these exact samples) using gas
chromotography showed the measurements to be unreliable below 5 ppb. For this reason only
an upper limit is quoted in appendix 3. For future work, samples are being sent to other
laboratories and a better detection apparatus will be obtained.
The measurement of Coliform Bacteria:
The measurement of coliform bacteria is, in principle, much simpler than the
measurement of arsenic concentrations although again the reliability in practice is critically
important and the frequency of measurements needed for the dug wells is greater than the needed
frequency of arsenic measurements. However, many users of dugwells have found considerable
coliform bacteria. There is general agreement that measurement of coliform bacteria can be
reliable. For the first measurements Dhaka Community Hospital had no equipment of their own.
Measurements by other institutions were expensive and unreliable and are not reported here.
However in 2001 we acquired a “Delagua” kit17 designed at the University of Surrey and used it
for all measurements for the 66 wells reported here. More recently the coliform vial from a JALTARA18 measurement kit from CLEAN INDIA in New Delhi has been used to give an initial
qualitative test to determine whether a full measurement is necessary. The initial measurements
of the 66 dug wells in this project are shown in appendix 3. They were repeated by DCH every
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three months for a little over a year before handing over to the community managers. The initial
set of 5 – 6 tests is available on the web. Unfortunately the date of disinfection (with lime) was
not recorded but it is possible that it was shortly before the measurement so that the measurement
might not be a good indication of long term behavior. This may explain the fact that the
measurements of total coliform were low and of faecal coliform were consistently 0 whereas the
tests discussed in the next paragrpah were high..
In 2004 questions were raised about the quality of the DCH wells. Accordingly 20 of the
wells were tested again frequently for a year (July 2004 to June 2005). A different coliform
measuring equipment was used – from MacConkey, because the culture medium, MacConkey
(purple) broth is more readily available in Bangaldesh, than the culture medium for the Delagua
kit (membrane Lauryl Sulphate Broth). This time, tests were only made for faecal coliform and
not for total coliform. The measurements revealed problems of which we were not aware. It
can be seen from a plot for 6 of these wells in figure 2 the coliform bacteria levels were high in
July 2004, and were therefore in violation of the present standard, but soon dropped to less than
10 structures per 100ml (although one rose again).19 It is unclear why. This was the first time
that the “multiple tube” method was used and the first meaasurement may have been an error. It
is also possible that the guardians of the wells had not applied lime when appropriate during the
previous 6-12 months. These faecal coliform indicate that the water may be contaminated with
human or animal wastes. In principle both the US EPA and WHO state that there shall be no
faecal coliform.20 Unfortunately the dates when liming and other maintenance was performed
was not recorded. Work is continuing to understand the reasons for the high levels when they
occur; and this will be used in recommendations for frequency of monitoring.
Figure 2
C o u n ts p e r 1 0 0 m l
C o u n ts p e r 1 0 0 m l
Faecal Coliform Bacteria
200
150
100
50
0
2
5
8 11 14 17 20 23 26 29 32
Months since January 2003
The capital cost of the wells was about $70,000. This cost does not include the cost of
DCH planning and supervision. The capital cost is falling with time as we learn how to use
indigenous materials and labor. Detail of the cost breakdown for different types of installation is
shown in appendix 2.
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Note to Editor
It seemed best to us to have this crucial detail in appendix 2. But you may prefer to omit it
entirely and we will merely say that it can be obtained from DCH or from the arsenic website.
Measurement of Manganese and other chemicals21
The first measurements in appendix 3 were of those pollutants that were easily measured
with the Delagua kit. But recently it has been suggested that manganese is a serious problem in
many surface waters and has effects upon health that can be as serious as those of arsenic.
Accordingly at our request BUET made a search for manganese. The WHO standard is 0.4
mg/l and most of the measurements were below 0.1 mg/l. In two wells at one time only, the
measurement was up to 0.6 mg/l. Details of the measurements are posted on the website22.
Acceptability
APSU performed a “Social Assessment” survey on the acceptability of the dug wells they
tested23 79% stated that they were acceptable. No specific surveys have been undertaken to
provide a quantitative level of acceptability.in this study. However on the various visits to the
villages, by one or more of the authors, subsequent to installation there has uniformly been
enthusiasm. Persons from neighboring villages have requested the help of DCH. In particular
enthusiasm has been shown for the distribution of water by pipeline because the distrance to
fetch water is important. This was not an issue or question in the APSU study (but see their table
4.7) . Since the addition to the cost is modest, and it enables more people to be served by the
same facility, we encourage that this improvement be undertaken at the same time.
We feel that any further discussion and verification of acceptability should be accompanied by a
“willingness to pay” for the improvements
In figures 2,3 and 4 below are shown photographs taken on one of these visits in 2004.
They show respectively a typical dug well with attached tube well, the water tank from which
gravity feeds the houses, and the tap with pure water in a lady’s kitchen for the first time in
history.
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Figure 3
Figure 4
Figure 5
Subsequent maintenance
It is a part of the whole principle under which DCH are helping the villages that the
villages own the wells and have the responsibility for their good operation. Nonetheless in the
short term DCH help. DCH has suggested a careful visual inspection every three months
Frequent measurements have been made on the 66 wells and on subsequent wells dug with DCH
guidance, so that the issues may be fully understood. In long term, many fewer measurements
are likely to be necessary. No problems of arsenic and manganese contamination have been
found, and it is unlikely that they would increase rapidly. Therefore we suggest that a complete
chemical analysis need not be frequent – maybe every 2 years. But, as noted above,
bacteriological contamination can be serious and can change fast.
So DCH is urging the community to call for measurements if and when any of the following
occur:
- after a visual inspection (to be carried out every three months) the well casing, or the apron
- surrounding the well seems cracked
- the water begins to smell foul
- the turbidity increases
DCH is preparing a detailed advisory and check sheet for this maintenance. Since as noted in
appendix 2 the maintenance can be an appreciable cost item, this remains an important
consideration for further study and elucidation.
Long term
We have always noted that a choice between acceptable actions could well be guided by
whether the action leads to a long term solution. In the long term we hope that most citizens of
Bangladesh will have access to publicly supplied pure running water where the concerns about
purity are handled centrally. We note that dug wells with a piped water supply have traditionally
been a step in this direction in many countries. For example, in one English village in which one
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of us lived for several years, an open dug well was used for centuries with a bucket for
collection. This well was covered and a pump installed about 1920; in 1939 a windmill was
installed to pump up water to a tank from which a pipe led to every house and cottage. In 1945 a
small petrol engine was installed for use when there was no wind. About 1960, a main water line
came within a mile of the village and it was easy to make a spur connection to the village supply
network. This, of course would also apply if water from a deep well were pumped to an
overhead tank for distribution.
Conclusion
The use of a sanitary (dug) well has been shown to be a satisfactory and reliable solution
for the provision of bacteria free, arsenic free, and running water in several Bangladesh villages.
The capital cost is about $5 to $6 per person. Crucial steps in achieving arsenic free and bacteria
free water seem to be:
Selecting a site suitable for a dug well (one in peat is sure to smell!)
Strict adherence to sanitary standards as discussed for example by WHO
Ensuring community participation, ownership and maintenance of each well
This pilot project has can be, and is being, extended considerably in the Pabna region
where there has been word of mouth communication creating demand by people from other
villages. The installation has been supervised by DCH personnel, but there is a steady increase
in the understanding of the villagers themselves. With the financial assistance of UNICEF,
DCH have also supervised (since 2003) the installation of 137 wells (but only 3 with pipelines)
in the Sirajdikhan upazila.24 In principle, sanitary dug wells could be installed in many other
parts of Bangladesh. DCH has at the time of writing supervised 224 Dug Wells, bringing pure
water to perhaps 50,000 people – but only 0.1% of the people in Bangladesh who are in need.
In all of these the same careful procedures are adopted. The original 66 dug wells described in
this paper were free of faecal coliform bacteria, and very low on total coliform, but about 18
dug wells dug later in the Sirajdikhan upazila had contamination after an unusually severe flood.
These were retreated by DCH and now all of them are safe and measurements show a zero or
very low coliform bacteria count. In 50 of these wells, the measurement of the bacteria count
(using the Delagua kit) and contamination by other metals has been verified by measurements by
the International Center for Diarrheal Disease (ICDDRB). These are noted in the list of
measurements for these wells that are on the arsenic website at:
http://phys4.harvard.edu/~wilson/arsenic/remediation/dugwells/Dugwell_tests_for_UNICEF.xls
or a shortcut: http://DCHtests.arsenic.ws
As the Dug Well option is further implemented it is important to use indigenous materials
and measurement techniques whenever possible. This concept was used in this “pilot” project.
A part of the pilot project was clearly to demonstrate all aspects of a remediation method including a measurement of its cost effectiveness. However, the resources of DCH are limited, so
that for widespread use of dug wells it will be necessary for other groups to come forward, learn
the details of the simple technology, and to work with, and supervise the villages in the same
way. Hopefully some group will take this next step during the coming year.
12 12
In addition to the dug wells, Dhaka Community Hospital has started to provide other
surface and sub-surface water-based alternative safe water options – 5 River Sand Filters (RSF),
9 Pond Sand Filters (PSF), and 1,122 Rainwater Harvesting (RWH) units in the arsenic affected
communities in collaboration with GoB, UNICEF and donor agencies. All work satisfactorily.
These pilot, demonstration, projects will also be available for others to follow. DCH also
provides training on arsenicosis and arsenic problems through its Institute of Family Health,
including training for oversees medical personnel e.g. the Nepalese Health Department. These
will be described in forthcoming papers.
Acknowledgments
It is a pleasure to acknowledge the help of the many others who made this work possible.
First and foremost, the OPEC fund for International Development and other donors who made
the project possible. CLEAN INDIA of New Delhi, started by Dr Ashok Khosla, has been
helpful in providing at low cost reliable test equipment. In addition Richard Wilson thanks all
the staff of Dhaka Community Hospital for their hospitality.
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APPENDIX 1
DETAILED GUIDELINES FOR THE CONSTRUCTION OF A DUG WELL
Note to editor. If you prefer not to include Appendix 1 we will here refer the reader to the
arsenic website and to DCH itself.
A. Dug Well (DW) Survey
1) A survey and collection of records (number, location, present situation) of any existing
Dug Wells in the area should be made
2) The reason that a Dug Well is unused should be determined. Attempts should be made to
renovate an existing Dug Well if possible
3) In case of non-availability of any such records, a test borehole should be made to make a
bore log at the site.
B. Site Selection
The following factors must be considered in selection of the site: –
1) Areas of peaty soil should be avoided for the Dug Well as these cause the water to have
an unpleasant taste and smell.
2) There should be a stable soil layer at the top (a clay layer is preferable)
3) Presence of sandy layer within 9 to 12 m (30-40') from ground level is desirable
4) The site must be at least 30' away from any existing latrine
5) The site must be at least 30' away from pond
6) The site must be at least 30' away from a river
C. Dug Well Configuration
1) Inner diameter is 88.2 cm (3') and outer is 1.17 m (4')
2) Depth of Dug Well varies with the soil condition and water availability of the site. Depth
should be such to ensure 1 to 1.5 m (3' - 6') water column at the driest period
3) Height of concrete ring is 29.4 cm (1')
4) Height of head wall is 1 m (3.5') above ground level
5) About 59 cm (2') apron is provided all around the well
6) 1.17 m (4') x 75 cm (2.5') platform is provided for Tube Well installation beside apron
7) Length of drain pipe attached with the Tube Well platform varies from 1.5 m to 3 m (5' 10')
8) Dug well should be covered to protect it from outside contamination ensuring proper
ventilation and sunlight. The cover is made following WHO guidelines. Or a 0.4m (1’4”)
wire mesh should be placed on the head wall, for ventilation and a roof on the top with
translucent sheet to facilitate illumination and sunlight.
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D. Manpower
1) Trained workers (mistris) must be used for construction
2) 6 workers (mistris) should be employed for construction work- 1 head mistri, 2 assistant
mistris and 3 local persons to help the mistris so that they become trained after
construction of a few Dug Wells.
E. Construction
1) The Dug well should be dug manually
2) The Dug well should not be constructed to a pre-specified depth. The required depth
will depend on the soil and water table conditions. Instead it is better to construct the dug
well in the dry season, with the objective of achieving about two meters of water in the
Dug Well upon completion. This procedure will ensure a sufficient depth of water to
remain serviceable year-round.
3) Concrete rings are inserted after completion of digging
4) Where the sub-soil formation is not stable enough, the method of caisson driving (widely
used in bridge construction), may be used
5) Where the self-sinking method is used, the first ring of the Dug Well should be robustly
fabricated with a cutting edge
6) To prevent sand boiling rings should be jointed together using cement mortar inside and
outside of rings and joint-less flexible PVC, floating pipe can be connected with the Tube
Well. Iron rings, connected with concrete rings, can be used to hold this flexible pipe
7) To prevent accidents, during construction of the Dug Well, due to collapsing of side-soil
and occasionally asphyxiation from carbon dioxide and methane gases - rope, ladder,
Bosun’s chair etc should be kept at the site. No one should be allowed to work alone.
F. Water Quality
1) 30 cm (1') layer of brick chips are placed at the bottom of the well. 1.8 cm or 3/4'' chips are
placed at the bottom in 10 cm (4'') layer, 1.3 cm (1/2'') chips are placed in next 10 cm (4'')
and 2.5 cm (1'') chips are placed in the last 10 cm (4'').
2) Water parameters should be tested in the laboratory at least two times a year. These
parameters should be: pH, color, turbidity, iron, manganese, chloride, total dissolved solids,
total coliform (TC), fecal coliform (FC) and arsenic.
3) Well water is cleaned two times a year. For this 2 kg lime is thoroughly mixed with 35 L of
water and then it is poured in the well. The well water is stirred and then kept unused for 3 to
4 days. After 3 days the well is unloaded. The well is then filled with fresh water seeping
from the aquifer.
G. Maintenance.
The village must form a committee to be responsible for regular maintenance. The best time for
cleaning is the period between March and April. 2 kg of lime is thoroughly mixed with 35 l of
15 15
water and then it is poured into the well. The well water is stirred and then kept unused for 3 to 4
days before use. Workers must be trained for this task. If maintenance is not regularly
continued it is possible, even likely, that the coliform count will rise and the water become
unsanitary. If all requirements are met, we have found that water is of good quality. However
the requirement of testing [(3)] should not be omitted.
DCH is preparing a checklist to make sure that these requirements are followed. A
typical drawing of a village layout, as posted for example in the nearest clinic, is shown in the
figure below.
Note to Editor
It seemed best to us to have this detail in appendix 1. It is a typical plan at the DCH clinic office
for consulation by the villagers. But you may prefer to omit it entirely and we will merely say
that it can be obtained from DCH or from the arsenic website.
Overhead water
tank
Electric pump
Figure 6
16 16
APPENDIX 2
Note to Editor
It seemed best to us to have this crucial detail in appendix 2. We are continually asked about the
costs and this seems to be the place to put them and the right amount of detail. But you may
prefer to omit it entirely and we will merely say that it can be obtained from DCH or from the
arsenic website.
Typical costs of different types of Dug Wells
excluding DCH supervision
1
Sl
1
2
3
4
5
6
7
8
2
Type of Dug Wells
3
Tap
Points
4
Families
Covered
5
Popul.
Covered
Average
Approx
Approx.
6
7
Total Cost
In Taka
Improved New Dug Well+ Pipeline Network+
8
50
250
83,260.00
Water Tank(Steel) + Water Tower (Steel Column)
Improved New Dug Well+ Pipeline Network+
8
50
250
92,760.00
Water Tank(Steel) + Water Tower (Brick Column)
Improved New Dug Well+ Pipeline Network+
8
50
250
98,610.00
Water Tank(Steel) + Water Tower (RCC Column)
Improved New Dug Well +Hand Tube Well
1
15
75
58754.00
Recondition Dug Well + Pipeline Network + Water
8
50
250
50,350.00
tank (Steel) + Water Tower (Steel Column)
Recondition Dug Well + Pipeline Network + Water
8
50
250
72,070.00
tank (Steel) + Water Tower (Brick Column)
Recondition Dug Well + Pipeline Network + Water
8
50
250
70,220.00
tank (Steel) + Water Tower (RCC Column)
Recondition Dug Well + Hand Tube Well
1
15
75
31,394.00
Note:- 1. Calculated at the rate of 1USD = Tk. 60.00
8
9
Per person
Cost In:
1388
Taka
Cl.6/
Cl5
333.00
USD
Cl.7/
Cl.5
5.5
1544
371.00
6.2
1643
394.44
6.5
979
839
783.00
201.00
13.0
3.3
1201
288.00
4.8
1170
280.00
4.6
USD
$
523
418.50
17 17
7.0
Table 4
Maintenance Cost (per well)
Material
Quantity
Price
Total Tk
Labor charge for cleaning
3 person
400
2000/=
Potash
100 gm
Lime
3 kg
30/=
10
Repairing and fixing broken, leaking and
other damaged parts
30/=
1000/=
Total:
3060/= ($51.00)
[Calculated at the rate of 1 $ = 60 Thaka ]
The annual expense for maintaining a dug well is modest and is borne by the village
community.) A typical cost breakdown is shown in table 4 above. Typically families pay 10 –
20 Taka per month (120-240 Taka per year) which usually includes 60 Taka for maintenance , a
small stipend for the caretaker as chosen by the village Option Management Committee (OPC)
and the electricity bill for the pump.
At the present time the cost of the measurements is borne by DCH.
Cost of full 15 parameter (including Arsenic) test
Performed Initially and when needed (biannually)
5500/= Tk ($95)
Cost of Preliminary Coliform test by Clean India(Jal-Tara)
Performed quarterly
$1 each $4 a year
Cost of faecal coliform (FC) measurement is
400/= Tk. ($7)
when indicated by Jal-Tara or other test (approximately annually)
.
18 18
APPENDIX 3
The initial measurements of the first 66 dugwells
More complete measurements are available at:
http://phys4.harvard.edu/~wilson/remediation/dugwells/DCH_Phase1_Bacteria_tests.xls
or http://DCHtests.arsenic.ws
Dhaka Community Hospital – Pilot Sanitary Dug Well Project – Pabna
Region
Department of Environmental Research Laboratory Report
Data
: Analysis of Arsenic & Bacteriological test in water samples
Method of Analysis (Arsenic)
: Silver Diethyldithiocarbamate Method
Method of Analysis (Bacteriolocical)
DW
Code
Name
FC = Fecal Coliform per 100ml; TC = Total Coliform per
100ml
Date of Fam Ph
As Cond. TDS Turb FC TC
Date
ilies
conc.
.
Install or
Covered
(ppm) (us) (ppm)
(NTU)
of
: Oxfam-Delagua Kit Method
Address
of
Caretaker
Renovate
Village
Union
WHO Guide Line Values 1996
Thana
6.5-8.5
First
0.01
850
1000
5
0
0
Testing
DWH -1 Md. Anowar Master
Maddhapara UBM - 01 TBC - 01 1999 Nov
12
7.0
<0.03
234
152
<5
0
1
20.06.01
DWH -2 Ramjan Ali Pramanik
Ruppur
UBR - 02 TBC - 01 1999 Dec
11
7.5
<0.03
212
138
<5
0
0
20.06.01
DWH -3 Md. Akbar Hossain
Ruppur
UBR - 02 TBC - 01 1999 Nov
10
7.1
<0.03
241
157
<5
0
0
20.06.01
DWH -4 Md. Tipu Sultan
Kazipara
UBM - 01 TBC - 01 1999 Dec
12
7.5
<0.03
265
172
<5
0
0
20.06.01
DWH -5 Govt. Idara
Bissanathpur UBJ - 03 TBC - 01 1999 Nov
15
7.2
<0.03
354
230
<5
0
2
20.06.01
DWH -6 Md. Masum Master
Sinduri
UBJ - 03 TBC - 01 1999 Dec
14
7.0
<0.03
310
168
<5
0
1
20.06.01
DWH -7 Md. Nasir Khan
Sinduri
UBJ - 03 TBC - 01 1999 Nov
13
7.1
<0.03
241
157
<5
0
0
20.06.01
DWH -8 Md. Mirja Abdul Halim Aminpur
UBJ - 03 TBC - 01 1999 Nov
10
7.2
<0.03
246
160
<5
0
0
20.06.01
DWH -9 Md Jamal Hossain
Aminpur
UBJ - 03 TBC - 01 1999 Nov
15
7.0
<0.03
260
152
<5
0
1
20.06.01
DWH -10 Md. Majnu Mia
Aminpur
UBJ - 03 TBC - 01 1999 Nov
12
7.1
<0.03
212
138
<5
0
1
20.06.01
DWH -11 Md. Hanif Sheikh
Kalikapur
UBJ - 03 TBC - 01 1999 Nov
15
7.0
<0.03
350
228
<5
0
2
20.06.01
DWH -12 Md. Ali Hossain
Kalikapur
UBJ - 03 TBC - 01 1999 Nov
14
7.0
<0.03
235
153
<5
0
1
20.06.01
DWH -13 Md. Kader Mondal
Kalikapur
UBJ - 03 TBC - 01 1999 Nov
10
7.0
<0.03
215
140
<5
0
0
20.06.01
DWH -14 Md. Samsur Hossain
Nayabari
UBJ - 03 TBC - 01 1999 Nov
14
7.2
<0.03
198
129
<5
0
1
20.06.01
DWH -15 Md. Jabber Master
Nayabari
UBJ - 03 TBC - 01 1999 Dec
12
7.1
<0.03
263
171
<5
0
0
20.06.01
DWH -16 Md. Abdur Rahman
Tangbari
UBJ - 03 TBC - 01 1999 Dec
10
7.4
<0.03
325
211
<5
0
3
20.06.01
DWH -17 Md. Sohorab (Police)
Tangbari
UBJ - 03 TBC - 01 1999 Dec
13
7.0
<0.03
349
227
<5
0
0
20.06.01
DWH -18 Md. Jahur Ali
Tangbari
UBJ - 03 TBC - 01 1999 Nov
13
6.9
<0.03
285
185
<5
0
3
20.06.01
DWH -19 Md. Lutfor Rahman
Tangbari
UBJ - 03 TBC - 01 1999 Nov
15
7.0
<0.03
168
109
<5
0
0
20.06.01
DWH -20 Md. Mojhar Sheikh
Kabaskanda
UBJ - 03 TBC - 01 1999 Dec
10
7.0
<0.03
365
237
<5
0
0
20.06.01
DWH -21 Md. Sohorab Ali
Kabaskanda
UBJ - 03 TBC - 01 1999 Dec
15
7.0
<0.03
265
172
<5
0
0
20.06.01
DWH -22 Md. Jalil Sheikh
Kabaskanda
UBJ - 03 TBC - 01 1999 Nov
10
6.9
<0.03
282
183
<5
0
1
20.06.01
DWH -23 Md. Juran Mondol
Kabaskanda
UBJ - 03 TBC - 01 1999 Dec
13
6.8
<0.03
320
208
<5
0
2
20.06.01
DWH -24 Md. Monnaf
Sinduri
UBJ - 03 TBC - 01 1999 Nov
12
7.0
<0.03
315
205
<5
0
0
20.06.01
DWH -25 Md. Abdur Rajjak
Master
Natiabari
UBJ - 03 TBC - 01 1999 Dec
15
7.0
<0.03
252
164
<5
0
0
20.06.01
19 19
DWH -26 Md. Sahadot Hossain
Natiabari
UBJ - 03 TBC - 01 1999 Nov
10
7.0
<0.03
346
225
<5
0
0
20.06.01
DWH -27 Md. Rohmot Ali
UBJ - 03 TBC - 01 1999 Nov
10
7.2
<0.03
292
190
<5
0
2
20.06.01
UBJ - 03 TBC - 01 1999 Nov
10
7.0
<0.03
304
198
<5
0
3
20.06.01
UBJ - 03 TBC - 01 1999 Dec
11
7.1
<0.03
269
175
<5
0
1
20.06.01
DWH -30 Md. Sattar Sheikh
Rajnarayonp
ur
Rajnarayonp
ur
Rajnarayonp
ur
Sibpur
UBJ - 03 TBC - 01 1999 Nov
10
7.3
<0.03
214
139
<5
0
0
20.06.01
DWH -31 Md. Ahmed Ali
Sibpur
UBJ - 03 TBC - 01 1999 Dec
9
7.2
<0.03
198
129
<5
0
0
20.06.01
DWH -32 Md. Mirza Ruhul Amin Aminpur
UBJ - 03 TBC - 01 1999 Dec
15
7.0
<0.03
282
183
<5
0
2
20.06.01
DWH -33 Md. Harun Uddin
Aminpur
UBJ - 03 TBC - 01 1999 Dec
12
7.0
<0.03
322
209
<5
0
1
20.06.01
DWH -34 Md. Hosen Sheikh
Aminpur
UBJ - 03 TBC - 01 1999 Nov
14
7.5
<0.03
187
122
<5
0
1
20.06.01
DWH -35 Imam Mirjapur Jame
Mirzapur
UBJ - 03 TBC - 01 1999 Nov
12
7.1
<0.03
189
189
<5
0
0
20.06.01
DWH -36 Md. Motaleb Hossain
Khas
DWH -37 Md. Chad Ali Kash
Aminpur
UBJ - 03 TBC - 01 1999 Dec
11
7.2
<0.03
340
222
<5
0
2
20.06.01
Aminpur
UBJ - 03 TBC - 01 1999 Nov
14
7.0
<0.03
241
157
<5
0
1
20.06.01
DWH -38 Md. Akkas Ali
Aminpur
UBJ - 03 TBC - 01 1999 Nov
10
7.0
<0.03
342
222
<5
0
0
20.06.01
DWH -39 Md. Sahabuddin
Master
DWP -40 Mukul Malitha
UBJ - 03 TBC - 01 1999 Nov
10
7.0
<0.03
305
198
<5
0
5
20.06.01
UIP - 01
TIC - 02
2003 Jan
40
7.5
<0.03
202
131
<5
0
1
25.01.03
UIP - 01
TIC - 02
2003 Jan
37
7.0
<0.03
172
112
<5
0
3
25.01.03
UIP - 01
TIC - 02
2003 Jan
53
7.1
<0.03
198
127
<5
0
0
25.01.03
DWP -43 Mrs.Rashida Khatun
Rajnarayonp
ur
Ruppur
(Malithapara
Ruppur
(Biswaspara
Ruppur
(Charabottala
Babulchara
UIA - 02
TIC - 02
2003 Jan
48
7.1
<0.03
211
137
<5
0
1
25.01.03
DWP -44 Md.Harunar Rashid
Durgapur
USA - 01 TSC - 03
2003 Jan
28
7.4
<0.03
222
144
<5
0
3
25.01.03
DWP -45 Mrs.Samshunnahar
Gopalpur
USK - 01
TShC 05
USA - 01 TSC - 03
2003 Jan
20
7.0
<0.03
282
183
<5
0
2
25.01.03
2003 Jan
35
7.2
<0.03
298
194
<5
0
5
25.01.03
DWH -28 Md. Ali Saheb
DWH -29 Md. Torab Ali
DWP -41 Mrs.Salina Khatun
DWP -42 Mrs.Samshunnahar
DWP -46 Md.Abdul Momin Khan Sayedpur
(Dangapara)
DWP -47 Md.Mojibur Rahman
Ahmedpur
USA - 01 TSC - 03
2003 Jan
32
7.3
<0.03
301
196
<5
0
0
25.01.03
DWP -48 Md. Khorshed Alam
Koromja
UBK - 04 TBC - 01
2003 Jan
28
6.9
<0.03
314
204
<5
0
1
25.01.03
DWP -49 Md.Mamunur Rashid
USA - 01 TSC - 03
2003 Jan
32
7.1
<0.03
382
248
<5
0
3
25.01.03
DWP -50 Md.Zinna
Sayedpur
(Ujanpur)
Ahmedpur
USA - 01 TSC - 03
2003 Jan
30
7.4
<0.03
203
132
<5
0
4
25.01.03
DWP -51 Md.Azim Uddin
Bhabanipur
UBR - 02 TBC - 01
2003 Jan
28
7.4
<0.03
168
109
<5
0
1
25.01.03
DWP -52 Md.Badsha Master
Durgapur
USA - 01 TSC - 03
2003 Jan
28
7.0
<0.03
321
209
<5
0
2
25.01.03
DWP -53 Sree Nironjan Kumar
Sagorkandi
UBM - 01 TBC - 01
2003 Jan
35
7.1
<0.03
354
230
<5
0
0
25.01.03
DWP -54 Md.Raton Chowdhuri
Arifpur
UPM - 04 TPC - 04
2003 Jan
15
7.3
<0.03
265
172
<5
0
7
25.01.03
DWP-55 Md. Abdul Awal
Bhabanipur
UBR - 02 TBC - 01
2003 Jan
27
7.0
<0.03
312
203
<5
0
5
25.01.03
DWP -56 Sree Sudha Ranjan
Shagorkandi
UBM - 01 TBC - 01
2003 Jan
26
7.2
<0.03
255
166
<5
0
8
25.01.03
DWP -57 Md.Rabiul Islam
Char Ruppur
UIP - 01
TIC - 02
2004 Jan
24
7.3
<0.03
265
172
<5
0
2
28.01.04
DWP -58 Md.Zahidul Haq
Char Ruppur
UIP - 01
TIC - 02
2004 Jan
25
7.0
<0.03
346
225
<5
0
1
28.01.04
DWP -59 Md.Shahjahan
Char Ruppur
UIP - 01
TIC - 02
2004 Jan
25
7.3
<0.03
269
175
<5
0
4
28.01.04
DWP -60 Md.Iddris Ali
Arippur
UPM - 04 TPC - 04
2004 Jan
39
7.0
<0.03
187
122
<5
0
2
28.01.04
DWP -61 Md.Shamim Hossain
Arippur
UPM - 04 TPC - 04
2004 Jan
27
7.4
<0.03
340
221
<5
0
1
28.01.04
DWP -62 Md.Mizanur Rahman
UBJ - 03 TBC - 01
2004 Jan
27
6.9
<0.03
241
157
<5
0
3
28.01.04
DWP -63 Mrs.Shahanara Lipi
Bishawnathp
ur
Dariapur
USA - 01 TSC - 03
2004 Jan
25
7.1
<0.03
305
198
<5
0
4
28.01.04
DWP -64 Md.Abul Raja
Birahimpur
USA - 01 TSC - 03
2004 Jan
28
7.3
<0.03
202
131
<5
0
0
28.01.04
DWP -65 Md.Habibur Rahman
Rajnaraynpur UBJ - 03 TBC - 01
2004 Jan
24
7.2
<0.03
211
137
<5
0
0
28.01.04
20 20
DWP -66 Md.Raij Shikder
Bhuya Para
UBR - 02 TBC - 01
2004 Jan
25
7.2
<0.03
282
183
<5
0
1
Reports of each of these conferences have been widely circulated and are, for example, available on the web at
http://phys4.harvard.edu/~wilson/arsenic/conferences/arsenic_project_conferences.html
2
Arsenic in Bangladesh: report on the 500 Village Rapid Assessment Project, Published by
Dhaka Community Hospital, May 2000
3
Groundwater arsenic contamination in Bangladesh: summary of 239 days field survey from August 1995 to
February, 2000 and 27 days detailed field survey information from April 1999 to February 2000
Printed by and available at: School of Environmental Studies, Jadavpur University, Calcutta - 700 032, India,
Dhaka Community Hospital, Dhaka –1217, Bangladesh, Richard Wilson Harvard University, USA.
Also available on the web at:
http://phys4.harvard.edu/%7Ewilson/arsenic/countries/bangladesh/BANGLAREPORT.html
4
6th Report on Arsenic Removal Plants: July 2004 Part B. Follow-up Study on 20 ARPs found to be functional
in March 2004,
School of Environmental Studies (SOES), Jadavpur University, Kolkata- 700032, India
Website: www.soesju.org
5
Report of Groundwater Task Force, Government of Bangladesh, Chairman Dr S.K.M. Abdullah. 2002.
6
Water and Sewerage Authority (WASA)
Ministry of Local Government and Rural Development, Government. of Bangladesh
WASA report of 2003
7
National Policy for Arsenic Mitigation and Implementation Plan for Arsenic Mitigation in Bangladesh
Local Government Division
Ministry of Local Government, Rural Development & Co-operatives
Government of the Peoples’ Republic of Bangladesh March 2004
8
WHO table of dug well recommendations http://www.who.int/water_sanitation_health/dwq/wsh0306tab8.pdf
9
J.K. Ahmad, B Goldar, and S Misra.
Value of arsenic-free drinking water to rural households in Bangladesh.
J Environmental Management, January 1, 2005; 74(2): 173-85.
10
Report of Bangladesh Arsenic Mitigation Water Supply Project http://www.bamwsp.org/news5.htm
11
Professor Charles Harvey, MIT, private communication
12
Only a web version of the report seems available.
http://phys4.harvard.edu/%7Ewilson/arsenic/countries/bangladesh/Chakraborti/Chakraborti%20Dugwells/Chakrabor
ti%20Dugwells.html
13
Risk Assessment of Arsenic Mitigation Options (RAAMO)
Phase 1 report June 2004 Arsenic Policy Support Unit (APSU) Government of Bangaldesh
available online at: http://www.apsu-bd.org
21 21
5
28.01.04
14
PK Aggarwal, M Dargie, M Groening, KM Kulkarni,and JJ Gibson
“An Inter-Laboratory Comparison of Arsenic analysis in Bangladesh” IAEA draft report available at:
http://phys4.harvard.edu/~wilson/arsenic/measurement/arsenic_inter_laboratory_comparison.pdf
15
Rahman M., Mukherjee D., Sengupta M., Chowdhury U., Lodh D., Chanda C., Roy S., MD. Selim,
Quamruzzaman Q., Milton A., Shahidullah S., MD. Rahman T., Chakraborti D. (2002)
“Effectiveness and Reliability of Arsenic Field Testing Kits: Are the Million Dollar Screening Projects Effective or
Not?”
Journal of Environmental Science and Technology 2002; 36(24); 5385-5394..
16
Cheng Z., Van Geen, A, Chuangyong, J., Meng, X., Siddique A., Ahmed K.M. and Ahmed K.M.
Performance of a household-Level Arsenic removal System during 4 months Deployment in Bangladesh,.
Environ. Sci. Tech. 38:3442-3448 (2004)
http://phys4.harvard.edu/~wilson/arsenic/measurement/ES_and_T.pdf
17
The Delagua coliform bacteria measuring kit from the Robens Centre, University of Surrey UK
http://www.robenscentres.com/delagua/index.cfm
18
The Jal-Tara pollution measuring kit from Clean India in New Delhi, India
http://www.cleanindia.org/jaltarakit.htm
19
Details are available on the arsenic website at http://DCHtests.arsenic.ws
20
Drinking Water Standards an Health Advisories EPA 822 B 00 001 (2000)
http://www.epa.gov/safewater/mcl.html#mcls
21
A. Opar, A. Pfaff, A.A. Seddique, K. M. Ahmed, J. H. Graziano, and A. van Geen
Responses of 6500 Households to Arsenic Mitigation in Araihazar, Bangladesh
Submitted to Health & Place, May 31st, 2005
22
At http://DCHtests.arsenic.ws
23
Risk Assessment of Arsenic Mitigation Options (RAAMO) Phase 1 report June 2004 Chapter 4 Arsenic Policy
Support Unit (APSU) available online at: http://www.apsu-bd.org/chapter_4.pdf
24
These UNICEF sponsored wells are formally included in the APSU study but none of the randomly selected
clusters were in the upazilla and none were installed by DCH. The entry referring to DCH and the implications of
their table 3.2 are therefore incorrect. Moreover, we believe that APSU erred in not distinguishing those wells
where WHO guidelines had been strictly followed and those that had not.
22 22