Adapting the Biosand Filter for Arsenic Removal

CAWST is working in Cambodia and Bangladesh, to help researchers to verify a household water treatment (HWT) technology that has been shown to remove arsenic from drinking water.

Arsenic contamination occurs when the arsenic from rocks and sediments dissolve into the water. Most arsenic contamination in water is a natural occurrence associated with river deltas and sediments such as the Mekong River and the Ganges River. Long-term exposure to high levels of arsenic can cause skin and organ cancers. Tens of millions of people are at risk - especially in low income countries where people have no alternative water sources.

Studies have shown that iron oxide (common red rust) can be used to remove arsenic through a process called 'adsorption', where the arsenic becomes attached to the iron oxide. The Kanchan (KAF) filter uses this technique, by passing arsenic-contaminated water over a five-kilogram bed of small common nails that over time, will rust and create iron oxide. The KAF is designed with a bed of nails in the diffuser plate of the biosand filter.

In Cambodia, the laboratory study phase was successfully completed in 2006 by the Institute of Technology of Cambodia (ITC) with support from CAWST and the Massachusetts' Institute of Technology (MIT). The 8-week laboratory study showed that the KAF consistently removes over 90% arsenic, total coliforms, and E. coli from arsenic-contaminated groundwater near Phnom Penh.

The next step is to conduct an 8-month field technical research program to evaluate the technical performance and limitations of the KAF under field conditions of rural Cambodia. This will be funded by the Asian Development Bank. If the performance is found to be satisfactory, a pilot demonstration project will be done to determine the applicability, long-term acceptability, and actual impact of using the KAF in rural Cambodian communities. In Bangladesh, a similar technology verification process is underway with the assistance of CAWST and its local partner organizations.