Chlorination of Surface Waters in Bangladesh

Jabed Youssuf and Golam Mostofa

Dhaka Community Hospital

Ahmed et al⁽¹⁾. presented in Science in December 2006 a pessimistic outlook for safe surface drinking water in Bangladesh based upon data and analyses in an earlier paper referenced therein. These authors analyzed a group of dugwells constructed with various degrees of caution, and in so far as we can tell, none were chlorinated..

Data on bacteriological contamination in wells dug according to WHO guidelines, and regularly chlorinated, suggest that this pessimism is unjustified. This work studied coliform bacteria in 20 wells constructed in the Pabna region. Coliform bacteria were close to zero soon after construction or after 3 month maintenance with lime. In 2004 chlorination was not thought to be necessary. But high coliform counts were observed during summer 2005. We chlorinated and measured bacteria starting in May 2006, with daily measurements in July and August 2006, when the soil is flooded, the filtering capacity is low. Before the tests, coliform levels were unacceptably high and fell to below 10 FC/100ml immediately after chlorination with chlortec.. Using the same method of reference 16 of Ahmed et al. (not easily available except on our arsenic website below), we find the risk of microbiological contamination is 5.10-6 DALYs, about the risk level of a deep tube well.

In West Bengal Chakriborti, and Hira Smith have successfully chlorinated dug wells. Islam reported that after chlorination water was coliform free for 2-3 weeks, but got worse rapidly thereafter. Chlorination could be done daily as Chakriborti suggested, but every two weeks is adequate. We suggest that measurements be undertaken in any other region where dug wells are proposed. We suggest that the National Water Policy enunciated in 2003 giving preference to the use of surface waters in preference need not be abandoned if chlorination is used.

Full details are available on the website at http://PABNA.arsenic.ws

They are also available from DCH and a full paper is in preparation.

We gratefully acknowledge the full support of the staff of DCH and of the Arsenic Foundation Inc. for financial support.

1. Ahmed, M.F., Ahuja, S., Alauddin, M., Hug, S.J., Lloyd, J.R., Pfaff, A., Pichler, T., Saltikov, C., Stute, M., van Geen, A. .Ensuring Safe Drinking Water in Bangladesh.

Science. Vol. 314. December 15, 2006.