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Dugwell Test and Maintenance
(Draft, September 03 by M. Khaliquzzaman)
1.
Water Quality Test in Dugwells
Water quality of dug wells has been reported to be highly variable depending on the
location of the dugwells. The main complaints are:
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Bacteriological contamination
Bad smell
Unacceptable Taste
High Turbidity
Unacceptable levels of As, Fe, Mn
Residual chlorine and DBP if chlorine disinfections is used
All these concerns have to be addressed in a test program for the water quality in
dugwells . Bacteriological (coliform) contamination is reported to be almost universal in
the absence of disinfections. If chlorine disinfections is used then residual chlorine and
DBP especially THM are of concern. Bad smell and taste reported for dugwell water in
many areas are not necessarily bad for health but these properties make the water from
wells unacceptable to the people. Taste and smell are also highly subjective perceptions.
As taste and smell in many cases are known to arise from organic substances, measure of
total organic carbon may be considered as more objective proxy for taste and smell. So,
TOC (total organic carbon) test should be include for DW water quality. However, it is to
be noted that taste can arise from iron content and other parameters. NAMIC data show
considerable Arsenic contamination of shallow groundwater (depth<50 ft). Properly
sampled water from DW should be tested for Arsenic also. When DW is in continual
use, it is the pore water rather than stagnant well water which is collected by the people.
So, sampling for Arsenic test must ensure that pore water is tested rather than the
stagnant well water.
2. Maintenance of Water Quality in Dugwells
Once the water quality is certified to be potable after construction, it necessary to perform
periodic tests to ensure potable quality of the DW water. Bacteriological tests have to be
done periodically as even disinfected wells become invariably re-contaminated with the
lapse of time. The periodicity for test has to be determined from experience as it depends
on the mode of use, water quality and disinfections procedure used.
In some areas graphical displays intelligible to the illiterate have been used which
appears to be a good practice. In such displays, a pie-graph painted on a tin plate with an
arrow denoting the quality of the water is utilized. Such a display is shown in the figure.
The pie-graphs have the following information: Green - Safe to drink; Orange – Caution;
Red – Unsafe and White – Dry. The arrow fixed on the circle is rotated according to the
quality of water. The position of the arrow on green will denote that the water is safe to
drink.
When the needle is on orange, it would signify caution which means that the water after
collection should be either boiled or treated with some chemical at individual's home or
filtered to remove bacteria. The red color denotes the water is unsafe for drinking and the
well should be cleaned and disinfected. White means that the well is dry. At these times,
people should go to the nearest non-contaminated source of water.
3. Preventive Maintenance and Water Treatments
Cleaning and disinfecting the dugwells have to be done periodically by trained
laborers to remove pathogenic bacteria. The collected water should be treated at
individual’s home when the arrow is in orange position, by one of the three following
methods:
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Boiling for more than ten minutes
Adding water purification tablets
Using domestic filter that removes harmful bacteria