Development of low-cost systems for safe drinking water in areas of Bangladesh and India affected by arsenic

Abstract

Safe water options for five arsenic-affected villages (Sarupie, Manikganj; Daniapara, Shirajdekhan; Babutepara, Muradnagar; Iruaien, Laksham; Rahulllabad, Nabinagar) in central Bangladesh were studied in order to assist the local people and to obtain an indication of general solutions to the arsenic problem that is currently affecting ~100 million people on the Indian subcontinent. Arsenic concentrations were measured in all drinking waters believed to be safe and in a random sample of "red" (unsafe) tubewell waters. Depending on geography, history of safe water sources and availability of pond/river, the options of dugwells, deep tubewells and sand filters were recommended for core village areas, combined with sustainable output testing and a distribution system to maximise the benefits of sustainable water output. Very shallow tubewells were recommended for testing in villages where dugwells were successful. Rainwater harvesting was not recommended, due to expense, small storage capacity and summer dry periods. Two dugwells of optimised design were constructed in Iruaien and Daniapara, each serving 50-100 families. The knowledge gained in the villages was incorporated into the first draft of a "Safe Water Book" for dissemination of honest and accurate information about solutions to the arsenic problem.

An air/iron treatment system was developed for removal of arsenic from tubewell water in locations where water treatment is the only option available. The system is based on the Bangladeshi "three kalshi" method, but optimised for efficient contact of water with air and iron. It can be constructed like a sand filter, and requires no chemical input, except for clean scrap iron. Spent scrap iron containing arsenic can be incorporated into concrete for safe disposal. A model air/iron system was constructed and run for two years to demonstrate the long-term viability of the device.

A colorimetric method, using silver diethyldithiocarbamate, was developed for determination of arsenic in the villages of Bangladesh. The equipment was adapted for rugged field use, and performed successfully without electricity or running water in improvised laboratory space in villages, providing linear calibrations 0-500 µg/L and a 2σ limit of detection of 5 µg/L.

The appropriate technologies that should be developed or optimised for the arsenic affected region are described and preliminary suggestions are given about means by which self-propagating solutions might be developed in villages to solve the arsenic problem.