Arsenic website project (remediation page)

Well switching

Left. a well painted green(water safe) and, right, one marked red(arsenic content is toxic).

This is in many ways the simplest, cheapest and most effective method of remediation. It is important to understand the causes of the availability of arsenic in the tube wells and the extent to which the problems can be avoided by careful choice of wells. John McArthur of University College, London, emphasizes that 75% of the shallow wells are doing what was intended - providing pure water. The general view is that 33% of the people in Bangladesh villages have switched wells in response to the general advertisement of the problem. The team of Columbia Uiversity and University of Dhaka scientists find that in Ariahazar Upazilla, where they have been working, 68% of people have switched wells. This well switching is the cause of the biggest number of persons now drinking arsenic free water who were not before. Yet in a Government of Bangaldesh survey, this still leaves 1400 villages without any well that is free of arsenic. Obviously, these villages are priority villages for the pilot projects for the various technologies discussed below. This issue was discussed by the Arsenic Policy Support Unit (APSU) now defunct in a report "not just red or green".

Various remediation Systems

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Small (Household) Scale Arsenic Removal
Use of deeper wells
Surface waters
        Sanitary dugwells
        River Sand Filters
        Pond Sand Filters
Rainwater collection and Storage

Large Scale arsenic filtration

Purifying the water by simple inexpensive means available to each household. Many argue that this last of the four solutions recommended in 2003 by the Bangladesh government, can only be a short term solution but the proponents are more optimistic. Several groups (in Kushtia in Bangladesh for example, claim lasting success. Others have not had such good experience. It was widely recommended in 1978 as an emergency measure but is hard to implement and maintain. An important facet of many of the early systems is that after a period of use there was and is a "breakthrough". The filtering action ceases, and even some of the arsenic previously trapped comes back. There has been a mixed experience. Dipenkar Chakraborti, Meera Smith and John McArthur all find that many systems have stopped working in many places in West Bengal . The reasons are unclear. Maybe it is because of the break through that is not understood by villagers, maybe because of clogging by iron. Not only is it a waste of resources but it is a tragedy of false hopes. As discussed further below, there is one system, the SONO filter, for which "breakthrough" has not been observed. For this system there is also local backup In Kushtia.
Drilling deep wells (150+ m) where arsenic contamination is at present smaller. This is being urged by UNICEF and Columbia University scientists. It will probably be fine for 75% of locations in Bangaldesh. But this solution may not be available everywhere. There have been some problems so that continued monitoring (yearly arsenic measurement) is recommended by all experts.
Encouraging a return to well constructed and sanitary, surface (dug) wells, in which arsenic contamination tends to be smaller than in the tube wells - even those on the surface. This, as noted below, is an option that is being studied by Professor Chakraborti, Dr Meera Smith , Dhaka Community Hospital (DCH), with some scientists in Harvard University. But they must be installed with care. This webmaster urges strict attention to WHO guidelines (which includes use of disinfectants). Chlorination was not at first used in Bangaldesh, although widely used in most other countries, but recent work by DCH suggests that chlorination at least every two weeks is essential - especially in the monsoon period. The necessary monitoring ( measurement of bacterial contamination) is uncertain but once a year may be fine provided chlorination is used, and provided it is done at a time of expected maximum pollution. In 2009 this is being studied further
Rainwater collection and storage. Again the long storage time needed from the time of heavy rain to the end of the dry season suggests the need for careful attention to sanitation.

Small (Household) Scale Arsenic Removal

    At the first International Conference on Arsenic in drinking water, held in Dhaka in February 1998 simple methods for each household to filter the water were suggested as an immediate short term solution. They have in common a series of containers. Water is poured into the top container and filters through sand and iron chips to the bottom container where the water is now free of arsenic. It was hoped that these methods would be easily used by villagers, would use local materials, and be affordable.    Several groups claim lasting success.
Here is a 2001 report of several systems by an independent company, WR Akins.

    Guy Howard of the Bangladesh Arsenic Policy Support Unit pointed out that there were, in August 2005, 100,000 household arsenic removal units in Bangladesh.   Dr Abul Hussam of George Mason University, with his brothers in Kushtia and Dhaka, designed and market the SONO/MSUK filter. 21,000 SONO filters have been distributed throughout Bangladesh by May 2006.   They are marketed from their base in Kushtia. 400,000 people drink water from these filters from may parts of Bangladesh as shown in the map.. PDF files of photographs and other details of the SONO filter can be downloaded.   Professor Abul Barkat of the University of Dhaka comments that they "have collected data for last four years (that's how long some of these filters are running). More than a billion liters of water has been consumed from these filters. The filter has been optimized to last for seven years minimum at a cost of $35.00"     The system is continuously being modified and updated.   The importance of the back up that is provided for the SONO filter is the example of a dozen filters that were supplied in the village of Eurian in eastern Bangladesh where Dr Chakriborti of Kolkata and DCH are working.   The tests, in 2005, of these filters in the field by DCH were far from satisfactory.   Dr Hussam believes this was due to a manufacturing defect that has now been corrected and the group has replaced the filters at no charge.   The test results of the replacement filters are excellent. This emphasizes the importance for this method, of expert back up. The need for expert back up probably applies for all mitigation methods!   A recent independent report on the SONO filter shows that this filter is playing a major role in reducing the Bangaldesh arsenic problem. Additional data on the tests on the SONO filter installed by BAMWSP-DPHE in Hagijang, Chandpurhas can be found here. Furthermore, the water quality test report on the SONO filter installed by the BAMWSP-DPHE in Gojaria, Munishijang can be found here.   The SONO filter by itself does not grow bacteria as shown in tests by Village Education Resource Center (VERC),

    In other locations problems arose.   According to the 6th report by the Jadavpur University team, 80% of Arsenic Removal Systems (ARS) in West Bengal are not functional. Not only is it a waste of several millions of dollars but also it is a tragedy of false hopes.    It was noted as early as 1998 that the systems then proposed all had a problem of "breakthrough"    After a certain time, the filtering action ceases, and even some of the arsenic previously trapped comes back.   The existence of the "breakthrough" was a primary reason that the filters were proposed, as stated on this site at the time, solely as a short term solution.    A possible reason for the failures is explained in this note from Professor McArthur. "Do they know the water is Fe-rich? If not, find a way to tell them. It might change their view of the matter, because, unless Fe is removed before the As plant, it messes up a good deal of the removal technology currently available: and, as an Fe-removal plant aerates and precipitates FeOOH, it removes most of the As. This is standard (old) technology. If they fund someone who does not know the water is Fe-rich (and most don't) they may put a big sum into methods doomed to fail. Attached is a good example: a year old and doomed to follow 20 or so other clones now abandoned that litter my field area in West Bengal. Raw feed is 900, output 300 and climbing, blocked by Fe most of the time: a disaster."    Another reason may be that villagers found them too complex to use.

    In this connection it is very encouraging that the SONO filter has so far experienced no breakthrough.    Whether the break though will come in 7 years, 20 years or not within a lifetime is unknown.   But this gives a user, and those recommending their use, enormous confidence.   It seems clear that the reliability and effectiveness of Arsenic Removal Systems depends upon the water chemistry, and probably on the maintenance.   It is also unclear whether laboratory experience is predictive of performance in the field. It is unclear to this webmaster whether the SONO or other filters work on all waters in Bangladesh; and if a particular ARS only works on some waters how to decide whether it will work on a particular village water and how to explain all of this to the villagers affected.

    In 1978 the Government Of Bangladesh   instituted a program now called BETV-SAM (Bangaldesh Environment Technology Verification-Support to Arsenic Mitigation) to verify the claims regarding the efficacy of Arsenic Removal Technologies and appointed BCSIR ( Bangladesh Council of Scientific and Industrial Research) to carry out this program. BCSIR is being assisted by OCETA (Ontario Center for Environmental Technology Advancement) of Canada. This program was supported by CIDA and BAMWSP (Bangladesh Arsenic Mitigation Water Supply Project financed by the World Bank).    Under the current GOB regulations, no arsenic removal technology may be deployed in Bangladesh unless it is cleared by the BETV-SAM program.    In February 2004 the first four technologies were approved for "provisional" use and are now being sold -READ-F, SONO 45-25 (the system noted above designed by Dr Hussam for which he has been awarded the Grainger challenge prize ), Sidko and MAGC/ALCAN. For three years the webmasters unsuccessfully tried to obtain a copy of the report but now the report of BETV-SAM has now been posted on the BAMWSP website and is copied here.

     It is noteworthy that releases of the test results failed to note the important fact that only the SONO filter had no 'breakthrough". In Nepal, the KANSHAN filter has been deployed by Susan Murcott but the webmasters have no test data thereon.

    A new system, Electrochemical Arsenic Removal (ECAR) has been developed at Lawrence Berkeley Laborotary is is now being tried in the field both in India and in Bangladesh.    This webmaster has no opinion yet on the relative advantages and disadvantages.

Medium (community) Scale Arsenic Removal

The pessimistic conclusions of Chakriborti and McArthur are also challenged in West Bengal by Arup Sengupta of Lehigh University , John E, Lee M. Blaney, Owen E. Boyd, Arun K. Deb, and the nonprofit organization Water For People and colleagues in Bengal Engineering College. Their detailed paper of the results of follow up on over 150 (now 200) medium sized systems seems convincing. As of June 2011 their Tagiore-SenGupta Foundation was awarded the first prioze of $50,000 in the Reed-Elzevier environmental challenge for this fine work.in West Bengal. The cost is about $1,200 for a unit which purifies water for 300 families or about 1200 people. This works out at $1 per person. We are delighted that the Silver award of the Grainger Challenge Prize of $200,000 has been awarded to this details of the award can be accessed here. Anyone interested should call Dr Anriban Gupta at Bengal College. As of June 2011 their Tagiore-SenGupta Foundation was awarded the first prioze of $50,000 in the Reed-Elzevier environmental challenge for this fine work.in West Bengal.

In 2006 this webmaster made a tentative conclusion: it is vital to have a village community that is committed to follow up maintenance and hopefully a nearby institution for expert backup information and advice. In 2011 he is more sure of this than ever.

Subterranean Arsenic Removal

In some places it may be possible to remove the arsenic by oxidiation of the aquifer. This is the aim of the Subterranean Arsenic Removal (SAR) technology proposed by Mukherjee of Kolkata, India. They cliam" This technology can transform the way arsenic is removed from groundwater in Ganges, Brahmaputra and Mekong delta where the arsenic is of arsenopyrite origin, saving millions of lives. This includes affected areas of India, Bangladesh, Cambodia, Nepal, Vietnam and Thailand. The technology is about to be implemented in Cambodia and Burkina Faso with the help of Royal University of Phnom Penh and ‘Friends in Action International’ respectively, subject to proper research. The technology is scalable from a production capacity of 10,000 litres/day (USD 4,000) to 1,00,000 litres/day (USD 20,000) for each plant, catering to the drinking water needs of 2000 to 20000 people, depending on the soil & water conditions." A couple of years ago Harvey tried expeiments along these lines with limited success

Use of Deep Wells

The information from well water surveys such as that of the British Geological Survey and Mott MacDonald shows that many deep wells, greater than 150 meters in depth, are free of arsenic. This seems to be confirmed by more detailed studies from an MIT/BUET (and others) group and a Columbia University group. Dhaka and the southern part of Bangladesh (where salt water enters the shallow aquifer) are mostly free of arsenic. The reason appears to be that there is a clay layer below the aquifer from which most tubewells take their water and these deep wells tap a lower aquifer. But this is not true, for example, in Jessore where there is no clay layer. It is claimed that these deep wells are cheaper than most other alternatives. As of 2009 this has been the major mitigation solution and is supported by the funding agencies, World Bank and UNICEF and the Department of Public Health Engineering (DPHE). More important, however, is that these retain much of the simplicity of the "ordinary" tubewells and require less care in construction and less maintenance than other solutions. Details are available in the report of the Ground Water Task Force, July, 2002 and a detailed report of the Deep aquifer Data base and Preliminary Deep Aquifer Map. (Local Governme/nt Division, GoB March 2006) Full Final report Contents , Chapters1&2 , Chapter3 , Chapter4 , Chapter5.1-5.4, Chapter5.4-5.44 , Chapter5.5 , Chapter 6 , Chapter7Con , Chapter8Ref , Chapter9Appendices. A comparison of the Bangladesh government reports in 2002 and 2006 shows the increased confidence in deep tube wells as the preferred solution for 75% of the country.

But there are potential problems that should be considered in any implementation:

    - if such wells are dug carelessly, and not properly grouted, there is a possibility of "shunting" the aquifers and allowing water from the higher aquifer to contaminate the lower aquifer.
    - it is unsure whether the lower aquifer is a "closed" aquifer from a hydro geologic point of view or whether it is as easily recharged as the upper aquifer.
    - It is unclear whether, in a longer term, pumping from these wells would increase the arsenic level.

    These can be checked by frequent (once a year) measure of the arsenic levels. If arsenic levels are rising, other solutions must immediately be found.   Since money would be saved by using this cheaper method, the money could be set aside for such eventualities in what, we all hope, would be a limited number of locations.    Such a commitment should be made in advance.     In 2002 many experts were dubious. Dr Dipankar Chakraborti was still cautious in 2005.   The report by the Arsenic Policy Support Unit (APSU) "Risk Assessment of Arsenic Mitigation Options (RAAMO)" finds little arsenic and almost no bacteria in a selected group of deep tube wells.   Nominally they were selected randomly but that means little since it is strongly believed that the quality of deep wells is very dependent on geography.   Nonetheless this is highly encouraging and suggests that some of the caution in the use of deep tube wells may not be justified.   Indeed this reviewer would emphasize that at the worst, a deep tubewell would produce arsenic-free water for 10-20 years, and might do so for well over 100 years.   Since the cost may be lower than other alternates, it would in most cases be well worth a try.

There are many indications that Manganese can be found in deep wells.    This can be a problem in itself.    A recent paper discusses the effect on school children

Return to Surface waters.

Sanitation

    The reason for installing tubewells between 1980 and 1998 was to avoid the problems of sanitation and in particular to reduce cholera.   If Banglaesh is to retrun to use of surface waters Although n 2003 it was the official Bangladesh National Water Policy to return to the use of surface waters whenever possible.   Yet the Report of the Committee on Surface Water Development and Management for Drinking Water Supply in the Arsenic affected areas of Bangladesh, July 2003 pays inadequate attention to assuring sanitation and in most cases, chlorination.     As a result many surface water solutions were construction with inafdequate attention.     One Non Governmental Organization (NGO), Dhaka Community Hospital, (DCH) has paid attention to sanitation from the outset and also, through its medical clinics, has considerabel community involvement.   This webmaster pays, and will pay especial attention to their work..

    There are three imporant steps.
    A proper protocol for construction
    A proper protocol for maintenance
    A proper protocol for chlorination if necessary

    The first two protocols will vary with the surface wter chosen.   But the clorination procedureapplies to them all.     In the western world, water from whatever source is first filtered to remove as much organic matter as possible and then chlorinated.    These are for example discusded in a historical paper by Okun.

It is now clear from measurements that chlorination can keep wells free of bacteria and should be done at least every 2 weeks. This is shown in particular by measurements by DCH of bacteria the wells in the PABNA region Although measurements continue, this problem which has set back the use of surface wells is probably now solved.

Another possibility is to accept the surface waters and filter them on a small household scale and then chlorinate the water. This is done in the Mukti Pani filter, proposed by Meer Hussein of Kansas. The webmasters have no measurements on the effectiveness of this and welcome any measurements that we can post on this site. Other filters exist for large scale bacteria removal such as the Pure Safe Water using filtration and ozone.

In the past (50 years ago) many of the villagers drank from "holy" ponds where the water was protected from animals and cattle. Many of these were unsanitary. It was to prevent water borne diarrheal diseases that the tube wells were suggested. A return to surface waters must therefore be done with full regard to better sanitation than before. In particular this webmaster recommends rigid adherence to WHO standards. Waters should be tested for coliform bacteria, not just once but regularly and in particular at the worst period - the end of the dry season. Disinfectants such as lime can work for awhile after complete cleaning, but regular chlorination is far superior. Use every 2 weeks is recommended. Indeed in the USA Some wells are chlorinated daily. Tests should be made before the disinfection, not only just afterwards, to be representatative of the worst time. Also in the rainy season when the ground is water logged and the ability to filter bacteria is lost. Public confidence was lost when water from the tube wells were found to contain arsenic. It was lost again when the Arsenic Removal Systems were not successful in many places. Confidence once lost is hard to regain. For that reason, among others, this webmaster recommends that in order to inspire public confidence these measurements must be available for public inspection (for example the measurements of the dugwells installed by DCH are in a directory on this website.)

Use of Dug Wells

DCH Dugwells list details
    Before the (cheap and simple) tube well was introduced, many villages dug wells to obtain surface water. However,   many, if not most, were NOT carefully installed, dug, covered, and chemically treated, and they were full of bacteria.    Successful projects involving sanitary dugwells exist in other countries, and some that may be successful have been reported but not yet in the detail to convince the skeptics that no coliform bacteria exist. Here the webmaster reports primaily on the work of Dhaka Community Hospital (DCH) .    The site selection is the first step in a construction protocol. Wells must be remote from latrines, old or new. Adetailed paper includes the detailed construction protocol.     WHO has suggested similar guidelines so has Chakriborti. Grameen Bank now has a similar list. They must be covered to prevent entry of animals and refuse but is aerated to allow oxidization. Water is taken out by a connected tube well and pump, making them as easy to use as a tube well. They are located at a distance from latrines including past latrines with their buried organic waste if possible.

    In many wells, the water is pumped by electricity to an overhead tank fro which PVC pipe leads to half a dosen taps in indididual houses or between houses.   This system of running water is popular, but cost of electricity prevents it being run continuously..

    The well maintenance is crucial. DCH has a protocol for this and will not help a village with a new well unless they agree to follow the protocol with a custodian to implement it.    But in the protocol for measurement DCH initially made an error. Initial measurements of 66 wells in the Pabna upazilla showed no coliform bacteria and it was incorrectly concluded that chlorination was unecessary. But later measurements of some of the PABNA wells showed high levels of faecal coliform bacteria.   Although the cause of the error is uncertain, it seems likely that measurements were made soon after cleaning and maintenance instead of just before.   All the DCH measurements are available in a directory, DCHTests, on this site.    DCHTests.   Chlorination tests were was begun in Pabna in 2006.    Household bleach (5.5% chlorine) was used.   The amount was determiend by a US EPA recommendation for "shock" chlorination and successfully brought the levels of coliform to zero.       It seems that three weeks after maintenance coliform levels rise again, and the recommendtion to each well custodian is to chlorinate weekly or at least biweekly. \

The simple, portable tests for bacteria are simple yes/no devices.   If chlorination gets the level to zer, as it is in the USA, then they work.   But in Bangakledsh this has proved difficult at a low, but non-zero level is accepted.   For this, there exists no cheap field test.

Reports on DCH work:
List of DCH Dugwells (224) as of May 2009
2nd phase (in html) and (msword)
       pipingto individual houses
       layout of the piping)
third phase in (msword)
pictures from the webmaster's visit
DCH Tests
       Initial tests 2001-2004 (EXCEL file)
       Measurements on 48 wells in Siridjikan
Dr Chakraborti reports on tests of 483 dugwells in West Bengal confirming that most are arsenic free. No measurements of coliform bacteria are available to this webmaster, but Dr Chakriborti recommended disinfection with chlorine once a month.

Project Well in West Bengal, directed by Dr Meera Smith, has published details on about 170 sanitary dugwells in West Bengal;   A detailed listing showed high initial levels of arsenic in two wells. These high levels went down with time. According to the most recent report suggests that they are chlorinated every 2 weeks,   and no high bcteria lvels re reported.   But it seems that the bacteria levels are not brought to zero

Meer Husain of Kansas has also joinned in recommendations for surface watrers with filtration and chlorination.

The status of the chlorination and coliform measurements is unclear to this webmaster.

    CRITICISM of dugwells

The Arsenic Policy Support Unit (APSU), a Bangladesh Government group, reported in June 2004 that 1,524 dugwells had been dug by 6 groups: BAMWSP, DPHE-Unicef, DPHE-Danida, World Vision, WATSAN, and Asia Arsenic Network. By 2009 it was orally reported that 4000 new dugwells had been built. Of these many, perhaps half, have been abandoned. Of the 240 DCH wells only 7 have been abandoned for various reasons.    This webmaster has been unable to find details of these other wells.

    The dugwells, with pipeline, are a further step in matching the history of the water supply in the small English village in which Richard Wilson lived from 1953-1955. For several centuries, a village well existed from which everyone drew water in a bucket. In the 1930s, the well was covered and a windmill installed to pump water to a storage tank with water supply to one tap in each cottage. The cottages were "modernized" by installing staircases to the upper floors to replace the ladder. In the 1940s a small petrol (gasoline) engine supplemented the windmill when the wind died down, and a bathroom was installed in the cottage in which Richard Wilson lived. In the 1960s, the main water supply pipe to the city of Oxford was brought within 1/2 mile and the village connected to main water.

    In 1998 it was a puzzle to many geologists, and even some hydrogeologists, why the surface wells were free of arsenic. For they seemed to be sample the same water as the shallower tube wells, and in many locations shallow tube wells showed concentrations of arsenic concentrations increaing with time. Why does this not happen in dugwells? This question, asked 6 years ago has never been satisfactorily answered. There are several possible answers. Firstly, over centuries people used dugwells, mostly unsanitary, but no arsenic problems were ever reported. Secondly the experience of DCH, Meera Smith and Dipenkar Chakraborti suggest a difference.    They claim that the shallow dug wells were likely to be less polluted than shallow tube wells because, being wider (often over a meter diameter) they allowed access of oxygen and so would oxidize dissolved ferrous iron and that would scavenge arsenic from the water. Also the top of the aquifer is the freshest, youngest water,   which has been most recently recharged by flood (rain) water,    and so the least likely to be polluted by iron reduction.   On coming to the surface in a dug well the water oxidizes and deposits arsenic, by co-precipitation with FeOOH or sorption onto existing FeOOH in the sediment.    This argument may not apply to a small dugwell where water is continually coming in from the side and aeration may not be complete.

    The dug wells generally sample water that is shallower than the shallow tube wells. Dug wells are dug until the water table is hit, plus a bit more. Those dug in December, when the water table is high, sometimes went dry in a dry year. They were often a bit shallower than those dug in May at the end of dry season. Shallow tube wells are sunk until the first good clean aquifer sand in found, then are made 20 foot deeper to accommodate the screen,   Much of the pipe comes in 20 feet lengths, so that "shallow" tube wells may be 20 to 30 meters deep (5-7 pipe lengths, including screen).

River Sand Filters

DCH River Sand Filters.
River water is often pure, but in tropical countries it is usually not. Nonetheless it may be collected and filtered. For example in 2002-2004 Dhaka Community Hospital using funds provided by UNICEF constructed 6 River Sand Filters in the Saridjekan upazilla. Water is pumped into a series of 6 tanks containing sand, from which it is pumped up to an overhead storage tank before being fed to a number of taps for the villagers. Although the supply for each of these systems is adequate (6 liters per person per day) for 250 families, only 107 use the water from the River sand filter (RSF1). The custodian of the system spontaneoulsy told this webmaster on his 11th January 2009 visit that he and the villagers are very happy with the system. Tests of water qualityb in 2007 and 2008 show consistently good quality in PSF1 to RSF4, but in RSF5 the coliform bacteria rise in the monsoon and the top layer of sand has to be replaced. Normally such cleaning is done every six months. Details of the construction, and Measurements are available on this site.

Pond Sand Filters

    It seems logical to collect river water in a pond, and then filter it naturally. Again this has been done for centuries. Then it can be filtered as it goes into a second pond by sand or soil. A pond sand filter can purify water for several hundred people so that the overall cost (per person) is about the same as a deep tube well, but it probably needs more careful maintenance.    The webmaster photographed one system in 2004.   At first it was not bacteria free but it was improved and is bacteria free now.   The Phase 2 report of May 2005 by the Arsenic Policy Support Unit (APSU) "Risk Assessment of Arsenic Mitigation Options (RAAMO)" tests 42 Pond Sand Filter systems and found that 95% had bacteria both in the monsoon and in the dry seasons. They attribute this to inadequate maintenance and poor filter depth. Again no indication was given that disinfectant (lime or chlorine) was used.    The webmasters have no record of tests with chlorination for pond sand filters, but suggest that chlorination be at least as often as the tests in dugwells.

The abstract of a comparative field study on the effectiveness of arsenic removal from groundwater by household sand filters is available on the ACS website.

    In India, the Jal-TARA Slow Sand Filter is a common water purification systems comprise of chlorination, coagulation and sand filtration techniques. Of all these techniques, sand filtration offers a chemical- free, reliable and economical treatment. Jal-TARA Slow Sand Filter is designed to treat drinking water using slow sand filtration technique as per the specifications of World Health Organisation (WHO). Jal-TARA filter is a biological filter merged with advanced technique of fabric protection to improve and simplify the traditional process of slow sand filtration. Two type of filtration act together to improve the quality of water: It consists of a gravel filter to remove turbidity, and sand bed filters to completely remove pathogenic bacteria from raw water.

    Meer Husain of Kansas has developed the Mukti Pani filter for filtering surface water and removing pathogens. He recommends chlorination of the water after filtration. This seems similar to the Jal-TARA Slow Sand Filter noted above. The webmasters have no information about any measurements of either filter. We would welcome any measurements to post on the site.

Rainwater Harvesting

Household tanks with a capacity of 3200 litres. Photo courtesy of UNICEF-Bangladesh.

Rainwater harvesting is extensively practiced in India (W Bengal). Attached is a comment by Dr Meera Smith.

For anyone unfamiliar with the cycle of monsoon rain and long dry season, it is puzzling why there is a problem in Bangladesh at all. One of the web masters lived in an English village where rain water harvesting and storage was usual. But storage was only needed for several weeks. In Bangladesh water must be stored for several (none!) months. The size of the tank must be increased tenfold, and it becomes difficult, although vitally important, to keep the water pure during storage. Nonetheless it is a solution for many communities where other alternates are not available. Particularly in southern Bangladesh, where there is frequent flooding, it is almost impossible to make a sanitary surface well, because it is not possible to keep the latrines at a distance from the wells. Rainwater harvesting is being advocated by UNICEF as reported by Dr Colin Davis at the 5th International Arsenic Conference in San Diego in July 2002. As of February 2004, 1000 new rainwater harvesting units were being installed by UNICEF and DCH

Simple storage of rainwater is not as simple a solution as it may appear from the above description. In some high-iron waters little or no arsenic is found. Everyone who has looked for microbiological contamination of such stored waters has found gross contamination - water containers act as incubators in the house, especially when they are uncovered or do not have taps. After 12 hours, fecal coliform can be more than 10,000/100ml, or even 'TNTC' (too numerous to count). The Phase 2 report of May 2005 by the Arsenic Policy Support Unit (APSU) "Risk Assessment of Arsenic Mitigation Options (RAAMO)" tests 42 rainwater harvesting systems. While less than half were contaminated by coliform bacteria in the monsoon period, this increased markedly during the dry season. A test of a rainwater collection system on the roof of Dhaka Community Hospital showed that chlorination reduced fecal coliform to less than 10 fc/100ml but they rose drastically again after 3-4 weeks. Chlorination of all rainwater tanks every 3 weeks seems desirable.

Various Charitable organizations are helping to bring pure water to Bangladesh and SE Asia. This webmaster suggests that you financially support one or all (any currency) and airline frequent flyer coupons gratefully accepted: