Scientists find solution to arsenic contamination in laterite soil

Laterite gravel

Kolkata: The simplest and cheapest solution to arsenic contamination of groundwater has been found to be none other the red laterite soil that is abundant in many parts of India, scientists said.

A low-cost, low-maintenance and eco-friendly indigenous water filter using laterite soil has been developed by a team of chemical engineers at IIT-Kharagpur which would dispense potable water at a cost of only 2 paise per litre.

Arsenic contamination of groundwater is a serious health issue in states like West Bengal, Bihar, Uttar Pradesh, Jharkhand, Punjab, Haryana and Assam. Most of the affected districts are located in the Gangetic or Brahmaputra river basin.

Prof Sirshendu De, who, over a period of 12 years, led the study that resulted in the innovation, told PTI that the novel idea hit them after they realized that places where laterite soil is found do not have have issues of arsenic contamination.

"We then started studying the nature of laterite soil and found that it is a very good natural absorbent of arsenic. And, after chemical treatment, the absorption capacity increases," he said.

The innovation, for which the IIT has filed two patents, has been licensed to a Jharkhand-based entrepreneur who is setting up a filter manufacturing plant at Kharagpur.

The commercial launch of the filter, which would include successive layers of materials, including bacteriostatic activated carbon, charcoal, fine granular sand, activated laterite and raw laterite, is expected in the next couple of months.  

According to World Health Organisation, drinking arsenic-laced water over a long period results in various health hazards, including skin problems, skin cancer, cancer of the bladder, kidney and lung, besides other diseases.

The IIT innovation, which has been praised by UNICEF's water, sanitation and hygiene specialist, SN Dave, has already been approved by the Union Ministry of Science and Technology, Arsenic Task Force and West Bengal's Public Health Engineering Department, said De.

Besides arsenic, the filter also removes iron and almost all pathogenic contaminants.

"Unlike in other filters, the arsenic doesn't at all leak from the laterite soil. We have tested that even during rains and heavy winds, the arsenic remains locked inside," the researchers said.

Laterite soil, also known as red earth, is rich in iron and aluminium.

Besides Kharagpur in West Midnapore district -- where the IIT campus is located -- the soil is found in abundance in two other districts of Bankura and Purulia in West Bengal.

Easy and free availability of laterite rocks makes the filter cheap to manufacture. The filtered water costs only 2 paise per litre.

The total capacity of arsenic removal in such a filter is found to be 32.5 mg/g, the highest among all available arsenic absorbents.