Scientists have found that dirty water can be sterilized and made drinkable by filtering through a folded cotton sari and then exposing it to sunlight for less than an hour. Nandini Nimbkar and Anil Rajvanshi of Nimbkar Agricultural Research Institute (NARI), a non-profit institution in Phaltan, Maharashtra, demonstrated the Cloth Filtration process which is already a common practice in rural India.
Disinfection of water may be accomplished by chemical treatment like chlorination or by boiling the water. Chlorination may alter the taste and have side-effects while raising the water to boiling may not always be possible with sunlight and would require electricity or some other fuel.
The water filtered through the tiny pores a four-layered cotton sari-cloth is heated to different temperatures ranging from 50 to 60ºc and analysed for coliform bacterial content. The experimental data shows that sari filtration alone — besides filtering particulate matter — significantly reduces the coliform count in the raw water. Heating the filtered water to 60ºc and maintaining this temperature for 15 minutes completely eliminates the coliform population. At 55ºc it requires 45 minutes for the water to become bacteria free.
NARI scientists have shown that disinfection could be achieved even at sub-boiling temperatures as low as 55ºc that can be reached using solar energy.