It started off as a puzzle for Sirshendu De, a professor at Indian Institute of Technology (IIT) Kharagpur. It was 2003 and the spectre of arsenic contamination of groundwater was looming large over West Bengal.
The solution to this puzzle led to the discovery of a way to filter the carcinogen that is now a threat to over 22 lakh people in India. Long-term exposure to arsenic in drinking water and food can lead to cancer and skin lesions and has been associated with the incidence of diabetes.
De’s ultra low cost activated laterite-based arsenic filter was one of the technologies showcased at the Festival of Innovation organised by the office of the President between March 4-10 in New Delhi.
At least 10 states in India are affected by arsenic contamination of groundwater and 7 of them - West Bengal, Jharkhand, Bihar, Uttar Pradesh, Assam, Manipur, and Chhattisgarh - have reported contamination levels that are above the permissible limit of 10 micrograms per litre (µg/L).
“We are worried and concerned, we are not able to give a solution to the problem,” NC Ghosh, a scientist at the National Institute of Hydrology in Roorkee who has been studying the problem for over a decade, said.
There are two ways to deal with the problem. One is to find ways to prevent contamination of the groundwater reservoir. But this is a challenge because the exact way the water is contaminated is still being studied. The other way is to treat the water at the point of usage.
The filtration technology developed by De’s team does exactly this. Their technology relies on a mechanism that is already present in nature. Laterite soil, which is present in some parts of West Bengal such as West Midnapore district, acts as a natural filter for arsenic.
The team found that the soil was able to adsorb the arsenic and then developed a filter which used a chemically treated variety of this soil that improved its ability to adsorb the arsenic. The filter that treats 100 litres/day costs about Rs 4,000 and can be used for 5 years with minimal operation and maintenance.
The Jharkhand government has already placed an order for these filters and they are in use in some districts of West Bengal. Other states may need to follow suit.
There are a handful of arsenic filtration technologies available but these have proved unviable because of their high purchase price and operating and maintenance costs. Expensive technologies cannot be used in areas affected by arsenic contamination.
“In most of the cases, because of operation and maintenance costs of these arsenic removal technologies, they are failing,” Ghosh said.
Over 80% of drinking water for rural areas in India and over 60% of irrigation water comes from groundwater aquifers, according to Ghosh.
When groundwater depletes it acts as a catalyst for arsenic contamination by leading to an increase in the chemical element’s concentration. Karnataka, with two of its districts susceptible to contamination, is also facing a decline in groundwater reservoirs.
One of the problems with other systems is that once the toxic substances are filtered there has to be an eco-friendly way of disposing of the filtered matter. For the IIT Kharagpur technology, the filtration system has to be disposed of after about 5 years and replaced. And the arsenic that is filtered does not leach so it is possible to dispose of the filters without harming the wider ecosystem.
It is possible to use the arsenic filtered in this way for laying down roads and pavements because it remains bound to the filtering material even in harsh environmental conditions, De said.
The IIT Kharagpur team applied for a patent for the filtration system in 2009 and are hopeful they would receive it in 2-3 years.
Meanwhile, the technology has been transferred to two companies, one of which is VAS BROS Enterprises, to promote its commercial use.