The DCH Dugwell Program in the PABNA region
Construction and Chlorination
January 28th 2008

(1)   (a)  Description of Construction.

Sakila Afroz Joya, Golam Mostofa, Jabed Yousuf,  Ariful Islam
One Solution to the Arsenic Problem: A Return to Surface (Improved Dug) Wells
Journal of Health Population and Nutrition 24(3) September 2006

     (b)  Pictures of the dugwells -  20 used for 2006 chlorination tests
            
(3)   Initial Measurements  These showed small coliform (often zero) but the measurements were probably made soon after  maintenance including liming.     While initially DCH thought that chlorination is unnecessary, this changed in 2005/6 as noted below.
 

(4)   2006 Chlorination tests:  May to November
       2006 Chlorination tests Daily in July and August  which is the rainy season when wet soil filters least and bacteria are likely to be worst.
        The amounts of chlorine are those suggested by USEPA. DrinkingWater Regulations and Health Advisories. Chlorination
Methods For Well Water. Scheduled D. Methods For Disinfecting Water Wells. October, 1996.
    Note that with biweekly chlorination faecal coliform average is below 5 structures/100 ml even in the monsoon period,  and 2000 less than upper limit for dugwells in Ahmed, Howard et al.    Note that since APSU is now defunct the Ahmed, Howard et al report cannot be obtained from APSU.   We scanned a version and post  here, in pdf, the scanned version but if anyone has an electronic version please send us a copy. 
    DCH now recommend chlorination at least biweekly

(5)         2007 Chlorination tests dueing Monsoon
    These were available in October 2007 and described at the meeting of the American Gelogical Society on October 31st 2007 in Denver, CO.   Because of the bad monsoon they are not as good as the 2006 tests.  In a bad monsoon weekly chlorination is important. A large INDIRA well in the Pabna region is better than the small wells (as expected).   An INDIRA well in Lakhsham is not as good as the INDIRA well in the PABNA region.

LOOK IN:
http://physics.harvard.edu/~wilson/arsenic/remediation/dugwells/DCHtests/Dugwell & Indara Result from July to Oct 2007

(6)  References to other (earlier) chlorination projects in Bengal (Bangladesh and West Bengal):

    (a)  Dipenkar Chakriborti of Kolkata has argued for chlorination for many years. 
    "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. Almost 2-3 days I do not use the dugwell (but stored water in the tank serves the need). 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. "
We have no references to Chakriborti's actual data but his strategies are here:

(b)    Nazmul Islam
Evaluation of Dug-well as a safe water alternative option
WATSAN partnership Project report 2004/1

This showed that bacteria increase 20 days after chlorination suggesting, as confirmed by DCH, that chlorination every 2 weeks may well be adequate.

(c)   The following is a report from Project Well in West Bengal.
    MM Hira-Smith, Y Yuan, X Savarimuthu, J Liaw, A Hira, C Green, T Hore, P Chakraborty, OS von Ehrenstein, and AH Smith
Arsenic concentrations and bacterial contamination in a pilot shallow dugwell program in West Bengal, India.
J Environ Sci Health (A)  Tox Hazard Subst Environ Eng, January 1, 2007; 42(1):89-95.

(d)  An excellent review paper describing how world wide approaches to sanitation have changed in the last 150 years, and especially how chlorination improved matters,  is by Okun.

Main arsenic website