The DCH Dugwell
Program in the PABNA region
Construction and Chlorination
April 30th 2007
(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
Pictures of 7 abandoned
dugwells
(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) References to other
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
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.