Cotton sari water filter: An indigenous water purifier for rural India that costs only Rs 1500


By Shilpika Srivastava

Talking about facts, there are 13% of inhabitants in Delhi who do not get water supply every day. If India’s national capital is dealing with such water crisis, think how acute the problem is in the rural areas.

Millions of people are still compelled to drink contaminated water leading to a series of health issues.  In rural India, thousands of infants die each year only due to diarrheal diseases, which are both preventable and treatable. According to World Health Organization (WHO), diarrheal diseases are the second leading cause of death in children under five years old.

The problem is so critical that even if we achieve the Millennium Development Goal of halving the population who do not have access to drinking water and sanitation by 2015, there will still be 244 million people in rural India and 90 million in urban India with no access to safe and sustainable water supply.

Keeping in mind the high cost of water purifiers available in the market and unavailability of electricity in rural areas, Nimbkar Agricultural Research Institute (NARI), an NGO working in rural Maharashtra, has developed a unique and low cost solar water purifier (SWP) for rural households. The best part is that it does not even require electricity or wastes precious water unlike the Reverse Osmosis (RO) systems.

“It took us about three years to develop SWP and total cost was Rs 20 lakhs. However, the major cost was spent on the staff,” told Anil K Rajvanshi, Director and Hon. Secretary, NARI, to NewsGram.

“We live in rural area and we have observed that because of poor drinking water there are a lot of diarrhea related health issues. More so with children and so we thought of providing a solution to it and hence the solar water purifier,” added Rajvanshi.

The low cost water purifier consists of four tubular solar water heaters attached to a stainless steel manifold. Unclean water is then filled in SWP after being filtered with a four-layered cotton cloth and then it is heated up in the stagnation mode by solar energy to make the water potable.

How it works?

SWP was developed in two steps essentially. The first step required a four-layered cotton sari cloth to filter unclean water. NARI explained that the tests done in its labs showed that such filtered water heated either to 60C for 15 minutes or 45C for 3 hours suspends all the coliform bacteria.

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Therefore, in the second step, the filtered water was then heated using the tubular solar collectors in the SWP in order to achieve a temperature of 60C for 15 minutes to kill the existing coliforms.

SWP has been tested extensively by NARI and it was found that even on a completely cloudy and rainy day, water is heated to high enough temperature to make water clean and drinkable.

How much it cost?

The main goal of NARI was to create a water purifier that could be easily afforded by the rural inhabitants.

SWP costs about Rs. 1,500 ($25), and is so simple that any small rural workshop can manufacture it.

The fact that should be highly appreciated is that NARI has not patented this technology since it believes that the purifier should be made freely available for rural population.

“I have always believed that availability of clean drinking water to every citizen is a birth right and every government of the day should provide it. You may be able to live without food for 5-10 days but cannot live without water for more than 5 hours. Clean drinking water is extremely important for health. The difference between poverty and affluence is the availability of clean drinking water,” said Rajvanshi.