ONE SOLUTION TO THE ARSENIC PROBLEM:
A RETURN TO SURFACE (IMPROVED DUG) WELLS
Sakila Afroz Joya, Bivash Chandra Barmon, Ariful Islam, Golam Mostofa, Altab Elahi, Jabed
Yousuf , Golam Mahiuddin, Mahmuder Rahman, Quazi Quamruzzaman
Dhaka Community Hospital
Richard Wilson
Department of Physics
Harvard University
A brief history of Worldwide Arsenic Use
Arsenic has been used since 3000 BC (Partington, 1935). In the United Kingdom, for
example, it was used to extract iron from iron ore. It has long been known that arsenic is acutely
toxic. Anyone who drinks arsenic in water at 60 parts per million (ppm) will soon die. Miners
took particular precautions to avoid exposure. Arsenic was also used for criminal purposes to
poison a rival and may for example have been used to poison Napoleon in his exile.
However, chemicals and substances are often only dangerous at high doses. Indeed at
lower doses beneficial effects can often occur. Arsenic has been used for about 2 centuries for
medicinal purposes. At fairly high doses it was successfully used as a cure for syphilis before
antibiotics entered the pharmacopoeia 70 years ago. Arsenic in moderately high doses repeated
over a month has been shown to assist in curing some leukemia (Soignet et al. 1998). In a 1%
solution of arsenite (Fowler's Solution) it has been used for nearly two hundred years since Dr
Fowler of Edinburgh recommended its use. That arsenic at low levels is safe seemed to be
reinforced by animal studies that seemed to show that arsenic is beneficial (to animals) at low
doses. Indeed, the fact that laboratory animals (mice, rats, cats, and dogs) could not be persuaded
to develop cancer misled toxicologists throughout the world and greatly contributed to the
present catastrophe. Others have written about other possible beneficial effects at very low
levels.
Thus a myth developed that while the acute effects of a large single dose are lethal, the
chronic effects of a small repeated dose were either small or beneficial. But we now know that
this perception is wrong.
Another myth is pervasive throughout society and across cultures. That the effect of an
ingested or inhaled substance is either adverse or beneficial but not both. We now know that it
can be both simultaneously, even at the same dose, with one medical outcome being beneficial
and another adverse. For chronic exposures, the adverse effects of arsenic dominate.
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A brief history of water use in Bangladesh
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Water is life. Water for human consumption should be potable, which should be:
Easily accessible
Adequate in quantity throughout the year
Free from contamination
Clear
Pleasant to taste
Odorless
Arsenic free
Germ free
Toxin free
Acceptable
Affordable
Convenient
User friendly
Sustainable
People of Bangladesh in the past 40 to 50 years, have been abstracting this water from
ground water by sinking hand/shallow tube wells and deep tube wells for drinking and domestic
water and also for irrigation. The water available in the saturation zone (pores completely filled
with water) is known as ground water. Physically ground water is generally clear, colorless with
little or no suspended solids. The water is also free from diseases producing microorganisms,
which causes high prevalence of diarrheal diseases in Bangladesh. The only disadvantages are
due to high iron content (the iron makes cooked food blackish in color) and hard.
Ground water is available in large quantities in shallow depths. The amount of ground
water that can be obtained from an area depends on the characteristics of the underlying aquifer
and the extent and frequency of recharge. Betweeen 1980 and 2000, Bangladesh achieved a
remarkable success by providing 97% of the rural population with bacteriologically safe tube
well water. This success led simultaenously to a disaster. Rural people were made aware of the
importance of drinking bacteriologically safe water and rapidly developed their habit of drinking
Tube Well water. Unfortunately arsenic in shallow ground water aquifers is at an unacceptable
level. WHO estimated 30 million people of South East Asian regions are living with arsenic
(REF) but recent information suggests that 50 million people (REF) in Bangladesh is under the
threat of arsenic. However DCH estimates an even higher number - possibly 80 million people
are at risk of arsenic poisoning in Bangladesh. Of these a large fraction will develop skin
lesions of internal cancers as estimated, for example by Harvey et al. (REF)
Today possibly more than 3 million affected shallow tube wells are used for drinking
water. Out of the total 64 districts of Bangladesh, in 50 districts arsenic has been found above 50
µg/l (the recommended level of arsenic in drinking water of Bangladesh) and in 60 districts
above 10 µg/l (which is the World Health Organization (WHO) recommended maximum level of
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arsenic in drinking water).
Soon after the arsenic problem was discuvered, it was widely suggested that a simple
option is to drill te wells deeper – to below a clay layer where the water is relatively arsenic free.
But in some areas the deep tube wells are found to be already contaminated with arsenic so that
this is not a solution. Moreover it is feared that the deep aquifer may become contamitated with
use.
In some villages 100% tube wells are contaminated with high level of arsenic. DCH and
Dipankar Chakraborti, Jadovpur University, Kolkata, India, jointly surveyed on arsenic affected
areas of Bangladesh and prepared the following maps (Fig. 1&2). Similar maps have been
prepared by others such as the British Geological Survey (REF):
Figure-1
Figure-2
Moreover in Bangladesh the water demand is increasing rapidly. 82% of the water supply
system depends (in 2005) on ground water of which 95%goes for irrigation and only 5% used for
drinking and cooking. Continuous extraction of ground water, which is non rechargeable at the
same rate of extraction, resulting in severe lowering of the ground water level. According to the
WASA report 2003 (REF), the ground water level that was 11m in 1970s went down to 20m in
1980s. It is estimated that it will go below 45m by 2016. Which, it is predicted, will create a
severe crisis to meet future water demand. So we have to reduce the load on ground water use
and have to make alternative water supply options based on arsenic free surface water that is
abundant in Bangladesh and was historically the source of water. Surface water is abundant in
the wet season in Bangladesh. An estimated 795,000 million cubic meter of surface water is
discharged per year through the Gangaes and Brahmaputra. This is equivalent to 5.52 m deep
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water over the land area of 144,000km2.
The Government of Bangladesh (GOB) in its national policy on arsenic mitigation (REF)
gave priority to surface water use among other options. Most of the people used dug wells along
with other surface water sources before 1985 when tube wells were suggested and encouraged.
The only problems of these surface water options are contamination with high level of bacteria
along with few other contaminants (such as iron, and phosphate).
These can be overcome easily if the surface water can be treated and maintained
properly. Due to poor management and improper investment, we are hardly utilizing the
abundant surface water with which Bangladesh is blessed. Now time has come to protect our
next generation from drinking arsenic poisoned ground water by proper management of surface
water, which is an easily available and affordable water source for the people of our country,
and it is also easy to keep safe. In the past years DCH has established 224 Dug Wells, 9 Pond
Sand Filters, 5 River Sand Filters and 1,122 systems for Rainwater harvesting. The original 66
dugweels described in this paper but about 18 dugwells dug later in the Sirajdikhan upazila had
contamination after an unusually severe flood and had to be retreated by DCH and now all of
them are safe and working. Pond Sand Filters (PSF), River Sand Filters (RSF), and the
Rainwater Harvesting systems that are models of safe water provided by DCH are also working
satisfactorily.
The worldwide mistake
Starting about 1980 it was suggested that Bengalis, both in Bangladesh and West Bengal,
should switch from the use of the abundant, but unsanitary, surface waters, to the use of ground
water using simple tube wells. This seemed to have the advantage of vastly improved sanitation,
and hopefully a reduction in the incidence of cholera. This was particularly urged by a wide
spectrum of western agencies: the World Bank, UNICEF and The British (UK) Geological
Survey in particular. In retrospect it is curious that none of these agencies, and none of the
“bystanders” insisted, or even seem to have suggested, that the ground water be tested for arsenic
and other heavy metals. With 2,000,000 tube wells sunk by, or on behalf of, these agencies and
another 8,000,000 sunk privately it is surprising that not even a small sample of these wells were
so tested. Even if a sample of 100 wells had been tested in 1980, the agencies would have been
alerted.
Early warning signs of chronic adverse effects
As early as 1888 Hutchinson (Hutchinson 1887,1888) published data showing adverse
effects on the human skin from prolonged use of Fowler’s solution. Lung cancers were
attributed to inhalation of arsenic pesticides as early as 1897. Neubauer, among others, had
described arsenical cancers in 1947 (Neubauer 1947). Skin pigmentation, keratoses and skin
cancers were found by Tseng (Tseng et al. 1968, Tseng 1977) in Taiwan among people who
drank from arsenic contaminated wells (but no effect was seen below about 150 parts per billion
(ppb), which might therefore be a biological threshold). Dr KC Saha in Kolkata (India) reported
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in 1980 (Saha 2002) that there were cases of arsenic poisoning in West Bengal But these early
warnings were ignored.
The world was finally alerted to unusual risks by the report of a very high incidence of
lung, bladder and other cancers in Taiwan by Dr Chien-Jen Chen and colleagues (Chen et al
1985). It appears that there are no data on humans to contest the idea that prolonged exposure to
low doses is dangerous. But even then it took 10 years for everyone to respond. It is now
realized that the catastrophe is much worse than the well known catastrophes of the Chernobyl
nuclear power plant accident, the Bhopal isothiocyanate leak or the Kuwait oil fires. Yet for
30% of the Bangladeshi communities, pure water is still a long time away.
Dhaka Community Hospital
Dhaka Community Hospital was founded in 1988 and have 40 clinics dispersed
throughout the countryside. DCH became involved with the arsenic problem in 1996 when DCH
doctors working at an annual health camp at Pakshi, Pabna District first detected patients
suffering symptoms of arsenicosis. DCH lobbied extensively to establish this issue as a public
health problem and went on to work with Jadovpur University, Kolkata, India, to survey by
sample the whole of Bangladesh. Since then DCH has collaborated with various partners in
research into the problem and solutions for mitigation as well as conducting its own arsenic
projects.
The choice between solutions
At the first International Conference held by Dhaka Community Hospital in January 1998
held jointly with Jadevpur University, Kolkata, several solutions to the problems were discussed.
Either arsenic must be taken out of the water or an alternate solution must be found. There
seemed to be some important criteria that any solution must satisfy:
(1) A short term solution might be acceptable if it was implemented on a wide scale at once.
(2) A long term solution should fit into a national water policy
(3) There was no reason for delay; short term solutions should be implemented at once.
If there was delay, the short term quickly became a long term.
(4) A simple return to unsanitary surface waters is undesirable
The proposal that was made at once was to have a national survey of wells, and install
temporary arsenic removal devices. However 7 years later, there are many villages still without
pure water. The arsenic removal devices proved too hard for many villagers to use and many of
them were unsatisfactory and were abandoned. Accordingly DCH has since 2000 been
emphasizing longer-term solutions.
Two facets of an overall elimination of the Bangladesh arsenic problem seem to be
agreed.
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(a) There is no one solution for all places and communities. In some cases purifying the water
may be preferred; in others use of arsenic free water is easier.
(b) It is vital to involve the local community in the choice involved in the decision and even
more important in the follow up and maintenance.
(c) The solution in any community and location must be based upon the best possible scientific
understanding.
(d) Both anecdotal evidence and a detailed survey suggest that villagers are very interested in
running water in our near their houses and according to a recent survey seem to be more
willing to pay for it than running water than for arsenic free water. This makes it preferable
to use a solution which provides pure water at the same time as running water.
The solutions which meet these criteria seem to be:
1) Drilling deep wells (150+ m) to a deep aquifer, below a clay layer. Many hydrogeologists
suggest that this aquifer is replenished by water from the mountains rather than annually from
rainfall. 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. Although it is unclear whether
it will always remain so.
2) Encouraging a return to surface (dug) wells (DW), but with a strict adherence to WHO
sanitary standards.
3) Use of sand filters to filter pond water (PSF) or river water (RSF)
4) Storage of rain water
DCH chose the second of these, the use of dug wells, for their demonstration facility in
the Pabna district. This report describes three phases of the work, and some indication of
further development.
The DCH Dug well Demonstration (Pilot) Project
The project was made possible by charitable donations from a number of foreign
individuals and from the OPEC fund supplemented by locally generated funds. Although the
project has begun somewhat earlier, 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 serving 3,250 users. Careful measurement was made of the bacterial content of
each well. These wells were of different shapes and sizes, but all had in common the general
sanitation features. They were sited remote from latrines. They were covered to prevent the
entry of foreign matter, (animals, feces etc) and a small tube well and hand pump on the side
extracts the water. Chemicals were used in the initial installation and subsequent maintenance.
(See Appendix 1 for the detailed requirements recommended by DCH)
Bringing running Water to Houses
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 tank, from which it is
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gravity fed to a number (6 or more) individual houses. This has proved very popular and is a
major step toward the acceptability of this solution. It is interesting that another group (Ahmad et
al. 2005) has found by survey that the availability of running water is more important in public
perception than the fact that the water is arsenic free. Already in phase 1 one well was installed
with a storage tank. 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.
We believe that the positive experience with a pipeline system is a most important part of the
demonstarion, pilot, project and we suggest that it will be an important part any solution to the
arsenic problem since a pipeline system can be added, for exaple, to a centrally located deep tube
well. Another grouop, the Bangladesh Arsenic Mitigation Water Supply Project has stated its
intention of providing 30 pipeline systems (http://www.bamwsp.org/neos5.htm) CHECK
In all 66 sanitary dug wells have been installed in this demonstration pilot project. The
capital cost was xxx This cost is falling with time as we learn how to use indigenous materials
and labor. Detail of the cost breakdown is shown in Appendix 3. In figures 3,4 and 5 are
shown 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.
Procedure for the installation of 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. 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
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bottom to top and the rings are joined by cement to keep the well water safe from contamination
from contaminated surface 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.
Detail of Project Implementation
In the implementation of the Dug Well project, 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 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
20k 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.
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Site selection
Sites for wells were selected in highly contaminated areas. This was done after
consultation with the community. Preference was given to sitting the wells near the patient
families and the poor. 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.
Installation of dug well and pipe network,
1) The Dug well is dug manually
2) Concrete rings are inserted after completion of digging
3) To prevent sand boiling rings are jointed together using cement mortar inside and outside
of rings
4) Joint-less flexible PVC floating pipe is connected with the Tube Well . Iron rings,
connected with concrete rings, are used to hold this flexible pipe
5) To prevent accidents, during construction of Dug Well, due to collapsing of side-soil and
occasionally asphyxiation from carbon dioxide and methane gases- rope, ladder, a
Bosun’s chair and other safety equipment are kept at the site
6) A 30-40 feet drain is constructed at the ground level to avoid water seeping into the well
around the head wall.
7) An electric pump pumps water from dug well to an overhead reservoir, installed on an 15
feet tall iron stand, of 3,000 liters.
8) A main water supply pipe (made of 3/4'' plastic) is connected with the tank for
distribution of water to the household level.
9) 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.
Community meeting,
Various mobilization and motivational activities such as campaign, courtyard meeting etc
were conducted in arsenic affected villages that increased public awareness. Meetings with the
community were held in the target villages with the community. Local GoB elected person and
influential local people were present in meetings along with DCH personnel. Community people
including women, the poor and arsenic patients exchanged opinions and preferences about
mitigation options and identified their needs. Priority communities were selected from these
meetings. A beneficiary committee was formed for the supervision of each implementation. Each
committee was responsible to operate and maintain the option provided to them. DCH and the
committees worked together to plan option installation and maintenance. Committee also
decided the down payment and monthly charge for water use for each family. Money receipt was
provided to the user families after getting the down payment money. The head of the
maintenance committee signed a contract paper before installation began. This consent paper
covers detailing of the community contribution for the option selected.
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Water quality monitoring
One of the most important functions of the village committee is the continuous
monitoring and guarantee of water quality according to quality guideline prepared by DCH in
consultation with experts and according to the WHO guide lines. In this they 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.
The Importance of Measurements
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 and through DCH the wider
community. The measurements of this pilot project are available as an appendix to this paper
which is also on the web.
Measurement of Arsenic Concentrations:
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, (REF) 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”
(Rahman et al. 2002). There is hope on the horizon. Columbia University scientists claim that
the Hach kit can be reliable if used in a slightly different manner than recommended by the
manufacturer (Chen et al. 2004). Also CLEAN INDIA of New Delhi is developing a cheap,
efficient kit that shows great promise (REF).
More recent laboratory comparions of water
samples with the IAEA laboratory show that several laboratories are in compliance, and the non
compliance are often in the precision of the measurements that are less important for the present
purpose.
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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. 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 we aquired a “Delagua” kit (REF) 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 JAL-TARA measurement kit from CLEAN INDIA in New Delhi (REF) to
give an initial qualitative test to determine whether a full measurement is necessary. The
measurements of the 66 dug wells in this project are shown in Appendix 4. If water is impure
Fecal Coliform (FC) and Total Coliform levels (TC) would be in the thousands. It can be seen
that the coliform bacteria levels are low. Our confidence that this also applies for the first year
where measurements were inadequate comes from the failure to find, after diligent search, and
case of water borne disease: cholera, jaundice or diarhhea.
Further extensions of this project:
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 supervized by DCH personnel, but there is a steady increase in the
understanding of the villgers themselves. With the financial assistance of UNICEF, DCH have
supervises the installation of 137 wells (but only 3 with pipelines) in the Sirajdikhan upazila. 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. In all of them measurements show a zero or very low coliform bacteria
count. In some of them, the measurement of the bacteria count and contamination by other
metals has been verified by measurements by the International Center for Diarrheal Disease
(ICDDRB). 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 supervize the villages
in the same way. Hopefully some group will take this next step during the coming year.
In addition to the dug wells, Dhaka Community Hospital has started to provide other
surface and sub-surface water-based alternative safe water options (River Sand Filters (RSF),
Pond Sand Filters (PSF), and Rainwater Harvesting (RWH) in the arsenic affected communities
in collaboration with GoB and donor agencies. These pilot, demonstration, projects will also be
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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.
Conclusion
The use of a sanitary (dug) well has been shown to be a satisfactory solution for the provision of
arsenic free running water in several Bangladesh villages. The capital cost is about $5 to $6 per
person. Similar results for sanitary dug wells have been obtained in West Bengal by Smith et al.
(2003) and this paper.
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
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.
14
G. Maintenance.
The village must form a committee to be responsible for regular maintenance. 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.
APPENDIX-2
A typical water supply network
As drawn to supervise implementation
Electric pump
Overhead water
tank
Electric pump
15
APPENDIX 3
TYPICAL C APITAL COST FOR DIFFERENT TYPES OF IMPROVED DUG
WELLS:
Sl
1
2
3
4
5
6
7
8
Type of Dug Wells
Improved New Dug Well+ Pipeline Network+ Water
Tank(Steel) + Water Tower (Steel Column)
Improved New Dug Well+ Pipeline Network+ Water
Tank(Steel) + Water Tower (Brick Column)
Improved New Dug Well+ Pipeline Network+ Water
Tank(Steel) + Water Tower (RCC Column)
Improved New Dug Well +Hand Tube Well
Recondition Dug Well + Pipeline Network + Water tank
(Steel) + Water Tower (Steel Column)
Recondition Dug Well + Pipeline Network + Water tank
(Steel) + Water Tower (Brick Column)
Recondition Dug Well + Pipeline Network + Water tank
(Steel) + Water Tower (RCC Column)
Recondition Dug Well + Hand Tube Well
Total Cost
In Thaka
In USD
83,260.00
$= 1435
92,760.00
$= 1599
98,610.00
$= 1700
58,754.00
50,350.00
$= 1013
$= 868
72,070.00
$= 1243
70,220.00
$= 1211
31,394.00
$= 541
Note:- Calculated at the rate of 1USD = Tk. 58.00
16
Detail Cost of Annual Maintenance:
The annual expense for maintaining a dug well is modest and should be borne by the village
community. The best time for cleaning is the period between March and April. 2 kg of lime is
thoroughly mixed with 35 l of 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. (See Appendix 1) A typical cost breakdown is
shown in the table below:
Material
Quantity
Price
Total Tk
Labor charge for cleaning
3 person
Potash
100 gm
Lime
3 kg
Repairing and fixing broken, leaking and
other damaged parts
400
2000/=
30/=
10
30/=
1000/=
Total:
3060/= ($53.00)
[Calculated at the rate of 1 $ = 58 Thaka ]
Annual Cost 60 Taka per family or 12. Taka per person = 20 cents per person
Typically families pay 10 –20 Taka per month (120-240 Taka per year) This usually includes a
small stipend for the caretaker as chosen by the village Option Management Committee (OPC)
and the electricity bill for the pump.
17
Cost of Measurements
At the present time the cost of the measurements is borne by DCH.
Cost of full 15 parameter (including Arsenic) test
5500/= Tk ($95) Initially
Performed Initially and when needed (maybe every 5 years)
Cost of Preliminary Clean India Test (Jal-Tara kit)
Performed quarterly
Cost of coliform (FC) measurement is
400/= Tk. ($7)
when indicated by Jal-Tara or other test (approximately annually)
$1
.
18
APPENDIX 4
Detailed Measurements for each of the 66 wells
(Note to publisher. This is a long appendix but in our view it is an essential part of the
paper. However if it is desired not to print it, reference will be made to a version on the
web)
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20