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Thoughts on chlorination in BGD

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  • Richard Wilson
    Dear Colleague I hope you will forgive this fairly general circulation. But I want to get views on what one should do about chliorination in the small water
    Message 1 of 2 , Jul 1, 2009
      Dear Colleague

      I hope you will forgive this fairly general circulation. But I want to
      get views on what one should do about chliorination in the small water
      supplies of Bangladesh. I had some thoughts in January 2009 which I
      presented to DCH and others in Dhaka (and attached) but it turns out
      that they were inaccurate So I circulate these updated thoughts about
      purification, when necessary, of water supplies

      Dick Wilson


      Background and Mistake

      In January 2009 in Dhaka Community Hospital I mentioned chlorination as
      a subject that should now be automatic in Bangladesh to ensure pure
      water supplies. But I had a few things wrong.

      In 2002 it was hoped that tby following very strict construction and
      operating standards (now codified by WHO) it would be unnecessary to
      chlorinate the well waters. Indeed in a temperate climate that might be
      true. I have seen reports from those involved with the people in
      Canada�s NW territories �the first nation� people, that suggest that
      proper well construction is all that is necessary. This was also stated
      to me in 2005 in Vancouver by the Health Department of British Columbia
      who observed about the DCH wells that I was describing -�I wish I could
      get people in BC to be as careful in construction.� Advice from a
      southern university in type US suggests chlorination of well water.

      But bacteria were found in the wells anyway. In 2006, 2007,and 2008,
      Jabed Youssuf and Golam Mostofa of DCH had great success in cleaning dug
      wells with massive amounts of chlorine in household bleach The amounts
      were as high as EPA suggested in amounts sometimes called �Shock
      Chlorination�. Interestingly this had been tried on contaminated
      (flooded) tube wells with no success. It seemed possible just to use
      shock chlorination every 2-3 weeks but the taste of chlorine after its
      use made it difficult to persuade people when they saw no reason (on
      which I will comment later)

      Both Dr Jamie Bartram of WHO and Dr Windsor Sumg of Massachussetts Water
      commission recommended that I talk to Dr Daniele Lantagne of CDC. But I
      failed to understand one thing. She said that attempts to chlorinate
      well water never seemed to result in an excess of free chlorine and
      therefore was unlikely to be effective. This Tracy Han and Mostofa found
      for themselves in April and May this year. Dr Meera Smith has had some
      success in getting rid of bacteria by weekly chlorination at about 1/3
      the dose that Jabed and Mostofa used in 2006-2009. But a look at her
      data showed that she also did not get free chlorine. I am not sure what
      Dipenkar Chakriborti does in his Ashram. I suspect he adds chlorine to
      the tank and not the well.

      What do we do next?

      I visited Dr Eric Mintz of CDC on June 16th. In his office in Atlanta,
      GAt. He was very gracious and helpful. Unfortunately Daniele was out of
      town. Dr Mintz is Daniele�s administrative �boss�. He has been working
      on pure water for 30 years or so. The general approach of CDC starts
      with central water supplies which should be so operated that there is
      always a little fee chlorine at the tap. That they argue is the only way
      of ensuring that bacteria will not flourish although of course they are
      well aware that the aim is to have no bacteria and free chlorine may not
      always be needed. He understands and agrees with Daniele that
      chlorinating at the well is unlikely to eb successful, although for the
      larger wells it might work for awhile. His approach, exemplified by his
      advice to Chile, is to add a little chlorine in the pipe carrying water
      and checking for free chlorine at the tap. Such equipment exists for
      city water supplies and might be used in DCH supplies from the big
      INDIRA wells or River Sand Filters.

      �Point of Use� chlorination has been encouraged by a number of people
      who are helping developing countries. Typically a standard size water
      collection can is used, and every time water is collected an appropriate
      amount of bleach is added to give a little excess chlorine. The can does
      not seem to absorb the chlorine the way a dug well itself seems to do.
      But in the newer DCH wells water is pumped to an overhead tank for
      distribution by PVC pipe to a number of taps - maybe as many as 50 or
      so. He agreed with me that if one can get the right amount of chlorine
      in the overhead tank that might be ideal. It would be easier to get the
      custodian to chlorinate than each individual user at the �point of use�.
      Measurement of excess chlorine should be made at the tap - not the tank.

      We discussed a little how this could be done since the overhead tank
      system is not designed for this. Climbing up every night and dumping
      liquid or powder in the tank might be OK for a test, and that is what I
      have suggested to Jabed and Mostofa. But this is dangerous in itself if
      done regularly. Maybe one could put in an �on line � feed to the water
      from the well to the tank as Mintz suggested for the Chile water supply
      authority. I have not yet checked the cost and availability of suitable
      equipment. But it seems that all future overhead tank projects should
      have this in mind. I note that this applies to the overhead tanks being
      installed by DFID fed by deep tube wells. They may need chlorination
      although not as much.

      We briefly discussed whether the attempt to get arsenic free water
      should be delayed by the desire to also have bacteria free water. Dr
      Mintz seemed to agree that the problem of bacteria from a well built
      well even in a tropical country may not be as bad as arsenic. What
      matters is the bacteria level averaged over a year. The well known
      calculations of Howard et al emphasized the upper 90th percentile of
      measurements in various wells of year. Using their coefficients and DCH
      measurements Sammy Sambu and I came up with a number 1/10 as big. That
      would be unobservable. Moreover the custodians of all DCH wells have
      been alerted to look for epidemics of diarrhoea of which they find none.
      This makes it hard to persuade people to chlorinate because they see no
      need. If we go back one step further and consider the review by
      Professor Alan Smith at the March 2009 Bangkok meeting of the Howard
      procedure for calculating the coefficients relating health to bacteria
      level one IL believe that this should not be a stopping or delaying point.

      My suggestion, therefore, for the future:

      Do not worry about any wells not dug or mainained to WHO or DCH
      standards. They should probably be abandoned or reconditioned.

      Test a simple procedure (if one can find one) for chlorination at the
      overhead tank.
      Ensure that all overhead tanks have a simple way of adding chlorine
      whatever the source of water
      Don�t forget regular general maintenance and cleaning of any system
      Even rainwater collection tanks need regular cleaning and probably
      chlorinating after a few months


      Richard Wilson
      July 1st 2009





      I gues


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    • Greg Miller
      Aquifers will always contain bacteria, they are ubiquitous and naturally occurring. Most of the bacteria in aquifers are innocuous and will not cause human
      Message 2 of 2 , Jul 24, 2009
        Aquifers will always contain bacteria, they are ubiquitous and naturally
        occurring. Most of the bacteria in aquifers are innocuous and will not
        cause human health problems. Human heath problems occur with pathogenic
        bacteria in groundwater when they are introduced into the aquifer through
        poor management of human and animal wastes. This can happen from poorly
        constructed wells, or putting the outhouse too close to a perfectly
        constructed well. Shock chlorination of wells and aquifers is an
        ineffective method of trying to prevent pathogenic bacteria in water
        supplies. The best practice is not to contaminate the aquifer with fecal
        matter. Once contaminated, chlorination of water supplies in the pipeline
        or tank is the only effective way to ensure pathogen free water. The desire
        to maintain residual chlorine is designed to prevent re-infection of the
        water once stored or put in the distribution system. Shock the storage tank
        with chlorine (>5.0 ppm) and maintain a residual chlorine level of 0.5 ppm
        or greater and you could use the water from a cholera contaminated aquifer
        without ill effect. You will never accomplish the same level of protection
        by treating the aquifer. Protect your aquifer and disinfect your water in
        storage.


        Gregory P. Miller, Ph.D.

        GEOCHEMICAL
        PO Box 1468 (Mail)
        1711-G El Camino Real (Courier)
        Socorro, NM 87801 USA
        (575) 838-0505 office
        (505) 217-4809 cell
        arsenic@...




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