A new household arsenic filter has been developed under the Nepal Water Project. It not only removes the carcinogenic chemical but also pathogens, iron, turbidity and odour. It is simple and effective: field research shows arsenic removal is in the range of 85-95 per cent, but it's also relatively costly: US$ 20 (EUR 16.65).

The Kanchan filter comprises of iron nails, brick chips and sand. It works on a simple principle: when the nails are exposed to air and water, they rust quickly, producing ferric hydroxide particles. When arsenic-contaminated water is poured into the filter, the toxic element is rapidly adsorbed onto the surface of the ferric hydroxide particles. The arsenic-loaded iron particles are then flushed into the sand layer below. The layer of fine sand traps the arsenic-loaded iron particles in the top few centimetres, thus effectively removing the arsenic.

According to Andrew A. Meharg, a biogeochemist at the University of Aberdeen, UK, education is needed to make sure the units are maintained and arsenic contaminated waste is safely disposed of.

The new household filter is jointly implemented by the Massachusetts Institute of Technology (MIT), the Nepal-based non-governmental organisation Environment and Public Health Organisation (ENPHO) and the Rural Water Supply and Sanitation Support Programme.

Contact: ENPHO, Thapagaon, New Baneshwor, Nepal, enpho@mail.com.np

Source: Down to Earth (subscription site), 15 May 2005

Tags: water quality