Sponsor:
Water For People (WFP) (An affiliation of American Water Works Association) Denver, Colorado, U.S.A.Project Engineers:
Anirban GuptaRanjan Biswas
Department of Civil Engineering
Bengal Engineering College,
Howrah, West Bengal,
India.
Technical Advisors:
Arun DebRoy F. Weston Co.
Pennsylvania, U.S.A.
Arup K. SenGupta
Department of Civil and Environmental Engineering, Lehigh
University,
Bethlehem, Pennsylvania, U.S.A.
LEHIGH UNIVERSITY, Bethlehem, PA 18015, U.S.A.
| Far more catastrophic than Bhopal and Chernobyl disasters is the arsenic
inflicted crisis affecting millions of people in Bangladesh and in the
Eastern parts of India. Contrary to Bhopal and Chernobyl events, however,
arsenic crisis in the Indian subcontinent is more of a natural calamity.
Groundwater which is the primary source of drinking water for millions
living in rural and often poorly accessible areas, is contaminated with
high levels of arsenic (over 100 parts per billion) through geochemical
soil leaching. Unacceptably high arsenic concentration in groundwater is
not something unique and has been reported in many other countries including
USA. But never have the magnitude of crisis and the resulting tragedy been
comparable to what are being witnessed in the Indian subcontinent.
The picture shows signs of hyperkeratosis on the palms of a villager in Bangladesh resulting from arsenic contaminated water. |
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In many areas, villagers do not have access to any secondary source of drinking water. Simple-to-operate treatment units at the existing well heads are practically the only solutions to ensure supply of arsenic free water on a daily basis. To this effect, the Civil Engineering department at the Bengal Engineering College, Howrah, West Bengal installed eight well head arsenic removal units in the districts of 24 Parganas and Nadia. The project was financed primarily through a grant obtained from Water For People (WEP), an affiliation of American Water Works Association (AWWA) located in Denver, Colorado. The figure below shows the schematic of a typical well-head arsenic removal unit. It is important to note that every component of these arsenic- removal units was procured and fabricated locally.
The following are some salient features of these units:
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- The unit does not warrant any chemical addition or sophisticated control. All one needs to do are open a valve, operate the hand pump and then collect essentially arsenic free water in a container. Regardless of the extent of contamination in well water, the arsenic concentration in treated water will consistently be less than twenty parts per billion - the standard set by World Health Organisation for drinking water.
- The regeneration of the unit with caustic soda is required once in four months.The entire amount of arsenic removed can be easily converted into less than two litres of sludge and retained in a brick lined pit. To put a quantitative perspective, a 4ft by 4ft by 4ft pit is large enough to store the entire amount of arsenic laden sludge for over 10 years.
Cost Figures:
Each unit costs approximately Rs. 50,000 ($ 1250) and has the capacity to serve two or three hundred households. Villagers within a mile radius of these units are using this water for drinking and cooking. Intermittent regenerations (once in four to six months) of these units with caustic soda and acid have been standardised. Contrary to reservations in certain quarters, the villagers had no major difficulty in comprehending the underlying operating principles of these treatment units and are now collectively involved in day-to-day operation of these units in all eight locations. On the average, each family pays approximately Rs. 50 per month for the treated water to cover all related expenses for the upkeep and maintenance of these units while the poor are exempt.
