Author – Aseem Shrivastava
Rural India still suffers from unclean and impure water that is not safe for drinking. According to the World Resources Institute 54% of India’s total area faces high to extremely high water stress and nearly 600 million people are at a higher risk of water supply disruption. Only 59 out of the 632 districts were found to have ground water safe enough to drink. Further, the two consecutive droughts in India have aggravated the crisis, with water resources are highly strained and groundwater table depleted. In most places, the concentration of water pollutants and heavy metals exceed the national safety limits as well.
While most people in cities can afford water purifiers, people living in many places of our country still do not have water filtering facilities. In rural areas, even now people trek many kilometers to get a bucket of water for their daily needs. Sometimes they have no choice but to drink unclean water, which causes diseases like diarrhea and jaundice. This article presents some interesting low-cost water filtering innovations that have the potential to solve the potable water problem in rural India.
Low-cost Water Filter using Corncobs
Sripada Srisai Lalita Prasida, a 11th class girl from Delhi Public School Damonjodi in Koraput, Odisha has innovated a method for purifying water, using corncobs. She found that waste corncobs are able to absorb the contaminants by the principle of adsorption.
Corn cobs were taken in five separate used plastic bottles of two liter capacity each containing 400gm of dried longitudinal corncob sections, pieces of corncob, powdered corncobs, activated charcoal layered one above the other.
Lalita Prasida conducted chemical tests for various contaminants and biochemical oxygen demand (BOD), toxic shock syndrome, etc. in her school laboratory and NALCO laboratory. She found that:
- Colored dyes present in the effluents were adsorbed in the charcoal layers
- Suspended particles were adsorbed in the chaff layers of pieces of corn cobs
- Adsorption of gasoline waste was also found in the powdered corn cob layers. Further investigation confirmed that the rate of adsorption was directly proportional to the surface area of the adsorbents.
- Calcium and magnesium salts, detergents, gasoline wastes, colored dyes, suspended solid particles were found to be captured in the filtrate
One of the advantages of this low-cost technique is that it can be scaled up and used to clean up ponds, lakes etc. It will thus enable to open up a new market value of the corncobs that are currently considered as waste. Lalita Prasida won the Community Impact Award at the prestigious Google Science Fair in 2015 that was held at California, USA.
Water Purifier using Old Saris and Sun
Dr. Anil K. Rajvanshi, an academician at the Nimbkar Agricultural Research Institute in Phaltan, Maharashtra has developed a low-cost method to purify water that is of immense benefit to the rural population. He is a mechanical engineer from IIT-K and University of Florida and an experienced technocrat in renewable energy research and rural development.
Under Rajvanshi’s process, unclean water is first filtered by a four-layered cotton sari cloth. It is then filled into a solar water purifier (SWP) that consists of four tubular solar water heaters attached to a manifold, which heats up the water to purify it and make it potable.
According to Rajvanshi, the water gets heated up to 60°C for 15 minutes on sunny days or 45°C for three hours on cloudy days, inactivating all coliform bacteria. The collectors have to be very efficient to raise the water temperature above 45°C for more than three hours even on completely cloudy days. Tubular vacuum-based solar collectors that can store water up to 15 liters were used in his model.
This technology avoids the use of wood smoke for heating, does not waste water unlike RO purification and there is no issue of periodic replacements of candles. The cost of setting this system is just INR1,500 and anyone can install and fabricate it. Dr. Rajvanshi has not patented the technology and the technical know-how is made available free of cost at NARI Phaltan.
Water Purification using Hair
Two Assam-based scientists have discovered that oil pollutants can be removed with the help of hair. While hair does not actually absorb the oil, the oil does coat the hair, by latching onto cuticles on the hair shaft. Human hair can thus be modeled as a planar layer.
Nikhilesh Das, a physics major and Debanjan Mukherjee, an electrical engineer, experimented with a beaker of oil and water and succeeded in removing the oil with the help of hair. They then improved their model by adding bird feathers and wood saw dust. They then took the four beakers from their school laboratory and tested the efficacy of these ingredients in curbing oil pollution.
This simple low-cost and eco-friendly idea (since one waste is being used to clean another waste) can be used economically in oil refineries where oil slush needs to be cleaned. These youngsters have patented their findings and received a national award from the National Innovation Foundation in 2011.
Water filtration by bio-sand method
The Biosand Water Filter is an innovative filtering method that has been featured here despite being a foreign innovation, since it is very much utilized in rural India. Dr. David Manz, a former professor at University of Calgary, Canada, who has built expertise in water engineering and wastewater treatment developed this water filtration method using bio-sand.
The bio-sand filter is made of locally available materials such as cement, layers of sand and pebbles. It also consists of few inches of standing water layer known as the ‘bio-layer’. Dirty water is poured on top meets with the bio-layer where bacterial predation occurs. The organic material gets trapped at the surface of the sand, forming a biological layer. The water moves through the sand layers and, because of an electrostatic current, viruses adhere to the fine sand and get trapped within.
Over a period of one to three weeks, microorganisms colonizing this part of the filter devour the pathogens found in the water, thereby purifying water. All viruses and bacteria are adsorbed into the sand grains. Cysts and worms are removed from the water by trapping them in the void spaces between sand particles. The water then flows down to the pebbles and comes back up in an outlet tube, which is stored in a clean water container with a lid to protect it from recontamination.
Many NGOs in India like South Asia Pure Water Initiative, Dhan Foundation etc. are distributing bio-sand filters in 12,000 villages and have positively impacted more than 100,000 villagers in India.