Imagine if water could be made potable using a few pieces of cotton cloth, glass tubes and sunlight!
Nimbkar Agricultural Research Institute (NARI), an NGO working in rural Maharashtra, has developed a unique and low cost solar water purifier for rural households.
NARI’s innovative water purifier cleans the water in two steps. In the first stage, the water flows through four-layered cotton sari cloth to remove the particulate matter and then the filtered water is heated at 45 degree C for three hours, using the sunlight. “All the disease causing micro-organisms can be deactivated if water is heated either at 60 degree C for 15 minutes or 45 degree C for 3 hours,” says Anil K Rajvanshi, director, NARI.
The purifier has four slanting tubular solar water heaters attached to a manifold with a receptacle at the top to receive the water filtered through sari. Each tube has a capacity to hold three-litre water. "These tubes are made of toughened glass similar to the one used in thermos flasks. It helps in maintaining the temperature of the water long enough to sterilize it," he says.
The NARI purifier is based on the old method of filtering the water using a cotton cloth and boiling it to kill the germs. "The difference is we are using heat from the sun, which is freely available across India," he says. It purifies a maximum of 15 litres of water every day, enough for a family of four.
The purifier costs around 3500 rupees but it is one time investment. The cost, says Rajvanshi, can be brought down to 1500 rupees if it is mass produced.
The only consumable is the cotton cloth. It has to be washed everyday, and it lasts about a year.
The organisation is now exploring the possibility of scaling up this technology for village level application. The aim is to purify 30,000-40,000 litres of water for the entire village.