If you are looking at buying packaged water or planning to filter water at home, you would surely have heard of the reverse osmosis process, popularly known as RO.
This process is considered the cure-all for water-related problems, from dissolved salts and sediment to pathogens. The technology, invented in 1949, is well-proven; water is passed through membranes that filter out impurities and pathogens.
However, despite this, there are some drawbacks to the RO system. For one, a lot of water is wasted — nearly 80 per cent of water is rejected in the RO process.
The process also removes essential minerals, especially calcium and magnesium. These two elements are among the seven required by the human body.
The World Health Organisation recommends that total dissolved solid levels in drinking water can be as high as 500 mg a litre. But in many households where filters are used, the input levels are well below 300 mg and, after filtering, may drop below 100 as many filters remove salts for better taste. Discharging higher levels of salts back to the source leads to a ‘vicious cycle’ of filtering, says J Chandrasekar, an entrepreneur who works on water and sanitation solutions.
“One size does not fit all. You must first test the water before finding a suitable solution,” says Varun Sridharan, Director, Greenvironment Innovation and Marketing, which works with IIT-Madras to develop water-testing solutions. For instance, he says that in Maduravoyal, Chennai, which was an industrial area, iron levels were found to be very high. This can damage the RO filter. The solution is to filter the iron first.
Even where RO is suitable, power can be an issue. This is more so in rural areas, where power is not available. Crux Power, a renewable energy start-up based in Odisha, has come up with a solar-based RO filter capable of filtering 10 litres an hour. The units are developed in association with the Bhabha Atomic Research Centre, says Sameer Kumar Palo, Manager Crux Power.
Others like Chandrasekar have developed water filter solutions that require no power. His ₹750 device, developed in association with the Council of Scientific & Industrial Research (CSIR), uses the porosity of clay to filter impurities and pathogens.
The filters are quite versatile and have been running for over seven years without requiring replacement. In fact, many of these units have been deployed in balwadis near Chennai where ayah s have been maintaining it with ease.