Chlorination JAn 2009

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					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, 1991). 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. One reason, perhaps, is that chlorine interacts with

residual organic matter to produce chlorinated hydrocarbons that are, at high levels, carcinogenic

to rats and nice. 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 . Another possible reason is the undesirable taste and smell.

Whatever the reason, chlorination was not used very much in Bangladesh or West Bengal. But

Abu Hussam, the Grainger Prize winner, informed me that his father, the public health official in

Kushtia regularly distributed chlorine tablets to many villages.
         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 describeed 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 Sridjikan 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.. 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.

(Royal Geographical Society, 2006 and American Geological Society, 2006) 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 this. 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 litre (10 mg chlorine per litre) 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 tuimes 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 acheive 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

mexamples of the kit PUR from Proctor and Gamble

       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 aor 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

chlortech added to th well or tank to achive a staisfactory 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.   MIt will probbly be chaper 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 surprizing to me

that the upper limit of their measurements of 60 wells or so was very high - many thousand faecal

coliform per ml. Since I have been unable to find the details of the wells and timing of the

measurements, in spite of diligent enquiry, 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.

Safe Drinking Water Foundation, Canada,

Center for Disease Control

World Health Organization, household water:

 And :

Quick et al Bolivia
Quick et al. Zambia

Luby et al. Karachi, Pakistan

Lantagne et al. Kenya

Lantagne review of chlorination

Okun, 1991
Luby et al. 2006

Guy Howard, M. Feroze Ahmed, Abu Jafar Shamsuddin, Shamsul Gafur Mahmud, and Daniel


Risk Assessment of Arsenic Mitigation Options in Bangladesh

J HEALTH POPUL NUTR 2006 Sep;24(3):346-355

See also RAAMO final report:

Sakila Afroz Joya, Golam Mostofa, Jabed Yousuf, Ariful Islam, Altab Elahi, Golam Mahiuddin,

Mahmuder Rahman, Quazi Quamruzzaman, and Richard Wilson

One Solution to the Arsenic Problem: A Return to Surface (Improved Dug) Wells

Journal of Health Population and Nutrition 24(3) September 2006


By Daniel A. Okun, Honorary Member, ASCE

Kenan Professor of Environmental Engineerini. Emeritus, Univ. of North Carolina, CB 8060,

Chapel Hill. NC 27599

(Royal Geographical Society, 2006 and

American Geological Society, 2006)

the Committee
Surface Water Development and Management
for Drinking Water Supply in
the Arsenic affected areas of

i) Director General, WARPO                                           Convener
v) Mr. S. K. M. Abdullah, Former DG, GSB                             Member
vi) Professor Ainun Nishat, IUCN                                     Member
ii) Director General, Directorate of Environment                     Member
iii) Director General, BWDB                                          Member
iv) Chief Engineer, DPHE                                             Member

Representative of convener of National Arsenic Expert Committee

July 2003

Nazrul Islam

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