A revival of traditional water harvesting systems involving local communities could be just the solution to the arsenic menace in West Bengal. Through the efforts of R N Athavale, scientist emeritus at the National Geophysical Research Institute, Hyderabad, and the Centre for Science and Environment as the central secretariat (CS) of the National Water Harvesters’ Network (NWHN), attempts to provide arsenic - free water to affected communities in West Bengal have been initiated. Efforts to provide sanitary dugwells in two identified arsenic affected villages – Kamdev Kati and Ambika Nagar in district North 24 Parganas of West Bengal have started. If successful, this low cost option could be widely replicated in the region through non-government organisations or by the communities themselves.

The rationale behind this project is simple. Arsenic content beyond permissible levels is usually found in water from deep tubewells, at a depth of about 30m. On the other hand it is rarely found in phreatic or unconfined aquifers.

It is this very property of phreatic aquifers that will be exploited. These shallow aquifers will be tapped by dugwells to provide arsenic free water, which can subsequently be recharged by harvesting rain.

According to Athavale, dearsenification of pumped water i.e. removal of arsenic is not the only solution to the arsenic problem. "All available options must be explored and an appropriate technology then introduced," he feels.

In line with our desire to work through grassroot non-government organisations in West Bengal, the CS approached Debu Bandyopadhyay, former water resources secretary, to identify an effective organisation through whom the pilot project could be implemented. The Institute for Motivating Self-Employment (IMSE), a Calcutta based organisation was identified as the local partner by him.

A visit to Calcutta was then organised followed by a visit to arsenic-affected villages in November 1999. Accompanying Athavale and a CSE employee of the CS, was Dunglena, former secretary, public works department, government of Mizoram. A member of the NWHN advisory committee, Dunglena has been promoting rooftop rainwater harvesting in Mizoram.

At this point in time the options available for dealing with arsenic included:

During the visit to Deganga block of North 24 Parganas, the team visited two villages, Kamdev Kati and Ambika Nagar, to assess the extent of problem confronted by the villagers and also identify the villages for the pilot project. People in these villages have given up hope for any amicable solution to the existing problem.

A visit to the villages ruled out two of the options mentioned above. There were no tin or (Galvanised Iron)GI sheet roofs on the houses. The roofs are either tiled or thatched. It was felt that although rooftop water harvesting can be implemented with modified gutters, this could be deferred for the time being. With the water table in the villages being shallow, the option of recharging near a hand pump or converting a pukur in an infiltration basin was not considered appropriate for this area.

The result of drinking water with arsenic

The construction of sanitary dugwells thus seemed to be the appropriate strategy to pursue in the region. The area has top clay layer till about 6 m depth, underlined by a sand bed which is the first aquifer. As the water table is high, the maximum depth of the well would be about 10 m. At this depth, the water available would be comparatively free of arsenic, since it is not found in phreatic aquifers. Even if it has arsenic beyond the permissible limit, it will be oxidised and thus it will coprecipitate with the iron when exposed to aeration in an open well.

Interaction with the villagers revealed that microbiological contamination in the water from the dugwells was a major fear amongst villagers. Responding to their apprehensions, arrangements have been made to prevent biological contamination. Says Athavale, "Removal of bacteriological contamination nowadays is much easier than removal of arsenic from water."

A parapet wall and a circular cement path around the well will be constructed. A grill on top of the well would restrict people from direct withdrawal of water, at the same time exposing the water to aeration. A water pump would be installed along with a pipe, which would be connected to an overhead tank. Water from the well would be only used for drinking and cooking purposes. Chlorination would be undertaken if necessary.

The grassroots worker by virtue of staying in close contact with the villagers will help in establishing rapport with the villagers and sensitize the community, resulting in the formation of village level institutions which can then monitor the progress of the programme.During the second visit to the identified villages in January, the team was shown an old well near the temple.

The water from the well was tested for arsenic presence and also to confirm the hypothesis that water in sanitary dugwells would be arseni-free. The result of the test confirmed that the level of arsenic in water is well below the permissible level.

For effective implementation of the project, Biplab Halim, executive director of IMSE opined that discussions at various levels-sabhapati, block development officer, pradhan and others, need to be organised. He emphasized that mass awareness should be the entry point activity of the project in each of the selected villages and proposed that a grassroots worker be placed at the Deganga block to oversee the project.