The Lmportance of Chlorination in Bangladesh

Tags Physics

The lmportance of Chlorination in Bangladesh

Richard Wilson

Department of Physics, Harvard University, Cambridge, MA 02138, USA

To be Presented to International Conference on Surface Waters

Dhaka Community Hospital, 190/1, Baro Moghbazar, Wireless Railgate,

Dhaka-1217, Bangladesh

January 15th 2009

Prior to the 1970s, the people of Bangladesh (then only 35 million) relied on surface water for their daily requirements. The water was directly taken from ponds and shallow hand pumped wells. But this water became increasingly polluted. The pollution stemmed from many sources including poor sewage systems in India and Bangladesh, and newly established industrial plants frequently dumped their waste in the water. This ultimately made its way into the low lying plains of Bangladesh. This contamination led to various health problems such as cholera and the extensive pollution of the environment. Western aid agencies, primarily the World Bank and the United Nations International Children's and Educational Fund (UNICEF) suggested a "solution" to the immediate problem of infection and industrial contamination. They advocated tapping the groundwater as a resource. This seemed to be a simple, cheap and effective, even magical, solution to the problem. Groundwater could be easily tapped by constructing a simple steel hand pump. Soon after, millions of dollars were spent on digging about 2 million shallow tube wells by western engineers and aid agencies. But no one told the government or the villagers to test for arsenic. The villagers dug more wells. Now there are over 11,000,000 tube wells tapping ground water. In the early 1990s, it was discovered that the well water, which had seemingly provided a solution to the country's water problems, came with a hidden poison. The water in nearly one third of the wells was laced with naturally occurring arsenic. No one had thought to check for arsenic contamination of well water when the wells were being dug.

The arsenic in Bangladesh is the greatest case of mass poisoning the world has ever experienced. In the sheer magnitude and in the numbers of victims it exceeds the Chernobyl disaster nearly 100 fold. In Bangladesh 97% of the population, or 116 million people ingest well waters. It was not until a major international conference in 1998 in Dhaka that the attention of the Bangladesh Government and international experts and donors was brought to the problem. The long term solution to the problem is a national water supply, where professionals take water from whatever source, purify it and deliver it to the consumers. Short and medium term solutions should bear this in mind and lead naturally to a long term future. In the intervening ten years the medium term solutions were discussed and implemented include:

(1) Use of deep tube wells that tap an aquifer below a clay layer where iron pyrites are not reduced to release arsenic

(2) Simple and reliable household filters to take arsenic out of the water.

(3) A return to the use of surface waters

This last seemed the obvious solution to many people. Bangladesh has a lot of water - too much in the monsoon period - so why not learn to use it correctly? In 2003 it was the official Bangladesh National Water Policy to return to the use of surface waters whenever possible, in spite of the fact that many communities have excellent water supplies from ground water (deep wells). But problems arose. A return to surface waters must be done with better sanitation than before to avoid the cholera and other water borne diseases that led to the use of tube wells in the first place. But leadership in sanitation in Bangladesh has been lacking in the last 10 years. In particular, Bangladesh failed to learn from the western experience of providing pure water which included filtration and chlorination (Okun, 1996). That experience enabled us to avoid typhoid, cholera and other water borne diseases. Western city waters are first filtered to be as free as possible of organic material, then bacteria are removed by a combination of ozone, and chlorination but there is always a little free chlorine. Attempts are made to ensure that there is still free chlorine at the tap at the end of a long pipeline. City dwellers such as myself have never lived in a community without chlorination.

It is unclear why chlorination has not been adopted by all the developing countries that try in many other ways to emulate the west. I remember lecturing on Risks to health in Islamabad in Pakistan in 1982. I pointed out that the hotels provided bottled water and recommended that no one drink the tap water. The chairman of the lecture, the Minister of Health of Pakistan, stated that he would never drink tap water without boiling it or adding chlorine tablets. Mexico traditionally had bad water and US tourists were advised to drink bottled water. Those who did not often got diarrhea, dubbed Montezuma’s revenge, referring to the slaughter of indigenous Mexicans by the Spaniards at the time of Montezuma.

One reason, perhaps, is that chlorine interacts with residual organic matter to produce chlorinated hydrocarbons that are, at high levels, carcinogenic to rats and mice. Although this is a very small risk compared with the other risks of impure water, this may have been the reason that the Peruvian government banned chlorination, but a cholera epidemic led them to chlorinate drinking water. Another possible reason is the undesirable taste and smell. Whatever the reason, chlorination was not used very much in Bangladesh or West Bengal. But Abul Hussam, the Grainger Prize winner, informed me that his father, the public health official in Kushtia regularly distributed chlorine tablets to many villages.

It might be argued that the wells dug by DCH are sufficiently good that it does not matter. This seems to be the case for the larger, INDIRA, wells in the Pabna region, even in the monsoon. But psychologically it has been a strong reason for opposing the return to surface waters which are the subject of this conference. I suggest that it is wise for DCH and others to address chlorination. Dipenkar Chakriborti of Kolkata, has argued for daily chlorination. His writings give no detailed measurements but in 2002 he has described on his website one large well system: "It is almost 3 years my model village people are drinking dug-well water. In my opinion my dug-well water is nectar, complete balanced cations and anions, arsenic 8-18 microgram/l and iron ~100 microgram/l. Please find herewith the photograph of my dugwell. I have two ponds near my dugwell with two cement storage tanks 20 ft X 20 ft X 5 ft. The tank is two storied. Between upper and lower tank people can rest in summer, as it is cold. Note my dugwell is 12 ft diameter with depth ~ 50 ft. It is a complete concrete structure. After two years of laboratory testing villagers are now allowed to drink the dug well water. To keep dugwell safe from bacterial contamination normally I make through cleaning twice a year and removing the sand and treating with KMNO4 bleaching powder and NaOCl. (For) almost 2 3 days I do not use the dugwell (but stored water in the tank serves the need). The most important fact even after cleaning everyday at night I put 2 drops of NaOCl per 5 liters of water. I know the water level and a simple calculation will decide how much NaOCl to be added. If you do it regularly bacteria contamination is not there. From my dugwell 800 people can drink water. "

Nazmul Islam of the WATSAN partnership in a 2004 report (Islam, 2004): He describes bacteria measurements in a number of wells. The measurements were not very detailed but he did point out that not only chlorination seems effective, but that bacteria levels tended to rise again after 3 weeks. That report was presented at an international conference in Dhaka Community Hospital in 2004 but not appreciated by this speaker.

But chlorination is not a panacea that can correct for all other deficiencies. It cannot by itself cope with many of the more recent problems. After severe flooding in Bangladesh during summer 2004 many inundated tubewells became contaminated by bacteria. “Shock” chlorine treatment by a single application of chlorine was ineffective in bringing bacteria levels down to acceptable levels (Luby et al., 2006). ICDDR’B also found shock treatment of flooded tubewells to be ineffective. In contrast, dugwells if so contaminated DCH has shown that they can be, and were, readily cleaned.

Dhaka Community Hospital (DCH) has also been an advocate for sanitary “improved” dugwells. Their procedure and guidelines are similar to those of WHO and are described in Joya et al. (2006). These satisfy steps (1) and (2) of western water supplies

(1) Choose a supply of water that is as clean as possible (or reasonable)

(2) Filter the water to remove as much organic material as possible

Nothing of what I say below is applicable to a situation where these criteria are not met. But I and DCH made a mistake. Starting in 2001 DCH measured bacteria in every well using originally a test kit from the University of Surrey in UK. As posted on the web and noted in Joya et al. they found no bacteria, or very few bacteria, in the wells dug in the Pabna region, and very few in wells dug and paid for by UNICEF in the Siridjikan region. This led us to believe, incorrectly, that chlorination was unnecessary. In retrospect it appears likely that measurements of coliform bacteria were only measured just after construction or just after cleaning with lime. They should have been measured just before maintenance since measured bacteria levels increase with time after cleaning the well.. Starting in summer 1996 and 1997 tests were made of chlorination and it was demonstrated that chlorination every week or two can cut bacteria levels to zero even in the monsoon period. These measurements were posted on the web and reported at conferences. (At the Royal Geographical Society, UK, 2006 and Geological Society,of America (2007) , available on the web. But villagers disliked the taste. I now argue that daily chlorination at a much lower level is likely to be acceptable and should become a normal practice.

I am not alone in arguing for chlorination. . Whereas 10 years ago the world ignored water supplies in developing country villages, attention has been paid by many organizations in the last 5 years. Wilkes University, USA, has instructions for owners of private wells in the USA. Safe Drinking Water Foundation in Edmonton Canada, and Center for Disease Control USA. There seems to be agreement that the doses DCH gave in 1986 and 1987, 0.2 ml of chlortech (a commercial bleach agent) per liter (10 mg chlorine per liter) was high, and although recommended by the US EPA (EPA, 2006) at the time it is appropriate for “shock “ treatment of a polluted well and not for regular use. The authorities above agree now that there should on a free chlorine level of 0.1 to 0.2 mg/liter, 50 times less. However, in an attached dosing paper CDC 0.2 – 3.0 mg/liter. But this must be maintained by daily addition of chlorine (every night) to the well or storage tank or both.

This immediately raises the question of how much chlortech to add to achieve this free chlorine level. These organizations have now also recommended test procedures and kits for quick test to see whether there is adequate free chlorine. The cost varies from a few cents per test or as high as a dollar per test. I have here a gift from CDC of such a test kit manufactured by Hach corporation sent to me by Daniele Lantagne, PE. an engineer at CDC who apologizes for not being able to get here because of a frantic schedule in many developing countries. I have also some examples of the kit PUR from Proctor and Gamble

One proposal by DCH, and ICCDRB has been to chlorinate at the point of use. There are recent papers showing that this reduces diarhoea in Karachi, Bolivia, Kenya and Zambia. I suggest that this be available as an option. I urge every agency of the government of Bangladesh to commit itself to chlorination. Even if the water is pure at the pump from a deep tube well, or as rain falls from the sky, there is much experience showing that bacteria can arise in storage containers and pipes. Pure water in the well or the storage tank is not enough. For the recent work of DCH where water is pumped to a tank and then to a pipeline, water must be measured at the end of the pipeline, and sufficient chlorites added to the well or tank to archive a satisfactory level. For our own part, the foundation of which I have the honor to be President, the Arsenic Foundation has committed some funds for Dhaka Community Hospital to carry out such tests and education, and we are funding an excellent Harvard University student, Ms Tracy Han, to spend 4 months here to help in the dissemination. Unfortunately she has an important examination next week (January 21st) so cannot be at the meeting. She will arrive January 23rd. I invite you all to support this push from the western world of the last 10 years to help in chlorinating the drinking water supplies of Bangladesh when it is necessary.

I have confessed to two errors on my part (firstly not chlorinating and secondly excessive dosing) over the years. Confusion has been caused also by others. In the desire to avoid arsenic contaminated water as quickly as possible many wells were dug and surface waters recommended which failed to satisfy the WHO standards. This was done by several, otherwise excellent, NGOs but not by DCH. In many cases even shock chlorination cannot clean them, as it failed to clean flooded tubewells. I suggest that all wells that do not satisfy WHO construction standards be rebuilt and reconditioned. It will probably be cheaper to do so that extensively purify the contaminated water.

Confusion has also been caused in a well publicized survey of surface water supplies (dugwells in particular) that combined wells of all sorts in an analysis. It is not surprising to me that the upper limit of their measurements of 60 wells or so was very high - many thousand fecal coliform per ml. Since I have been unable to find the details of the wells and timing of the measurements, in spite of diligent inquiry, I can only speculate that these high figures were in badly built wells with bad maintenance. I suggest that this survey be still used as a very strong warning of what can happen, but it need not be taken as an obstacle to wise use of surface waters with adequate chlorination.

REFERENCES

Websites

Arsenic website

Safe Drinking Water Foundation, Canada,

Center for Disease Control http://www.cdc.gov/safewater

World Health Organization, household water:

and :

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