Tata uses nano technology for water purifier | Centre for Science and Environment

Tata uses nano technology for water purifier

Recently, chairman of Tata group, Ratan Tata, unveiled a water filter called 'Swach' which uses nano technology to purify water. Tata Research, Development and Design Centre (TRDDC) and Tata Chemicals have jointly developed the core technology.

Swach is an advanced version of Sujal, launched around 2001-02 as a part of corporate social responsibility for Tsunami affected areas.

Technology used

Swach uses Rice Husk Ash (RHA) impregnated with nano (1 x 10-9) silver particles for safe and clean water. Sujal also used RHA in combination with pebbles and cement.  RHA, produced from heating rice husk, contains activated silica and carbon. Activated silica can reduce the turbidity of the water entering the filter and give a longer run for the system. On the other hand, activated carbon has the property to bind with non-polar materials while polar materials remain in aqueous solution.  Most pesticides are organic and strongly non polar and thus display an affinity for adsorption on the carbon surface. The activated carbon has a limitation in removing microbial contaminants. World Health Organization thus recommends coupling of charcoal treatment with chemical (iodine, chlorine etc) or UV disinfection to remove microbial pathogens. Activated carbon also cannot remove lithium, alcohols, ammonia, strong acids and bases, inorganic substances like sodium, lead, iron, arsenic and nitrates.

Non-profit organizations like Community Aid & Sponsorship Programme (CASP), Pune and Indian Institute of Youth Welfare, Nagpur who have helped TRDCC in distributing Sujal in rural areas, view that technologically there was no problem with the filter. CASP conducted laboratory tests to find out that the filtered water show a reduction of 96 % diarrhea and other gastrointestinal infection causing bacteria. Complaints are against the durability of the model and small size of the storage tank.  Chief Scientific Officer of Tata Chemicals, Dr. Muraly Sastry, explained that Sujal was successful in removing colour, odour and suspended particles from water but many pathogens found its way into the filtered water. They worked towards making the technology full proof. This time they have coupled RHA with nano silver.

Silver inhibits bacteria multiplication by reacting with sulydryl (-SH) groups in the bacterial cells, producing structural changes in bacterial cell membranes and interacting with nucleic acids. The nano sized particles help in increasing the surface area so that the bacteria get enough reaction time. Josh Kearns and Detlef Knappe of Aqueous Solution, research organization based in Huntington, USA, views that rice husks are just piled onto a fire and allowed to smolder. So the pyrolysis temperature is relatively low and oxygen is not well excluded - thus rice husk charcoal does not develop significant porosity and molecular surface area necessary for effective water filtration. According to a US Patent of 2000, the amount of activated carbon produced in rice hull ash depends on the amount of combustion. “We are not sure about the combustion temperature and process used by the rice mills owners supplying the RHA,” replied Sastry when asked about the production of RHA. The exact size and specification of the cartridge of Swach is still under wrap.

“Porous ceramic filters made from baked clay that includes rice husk, with colloidal silver, have been promoted by many organizations for many years -- the best known among them is Potters for Peace,” views Ashok Gadgil, Senior Scientist and Acting Director, Lawrence Berkeley National Lab, USA,  “Potters for Peace which appears to be very close to Swach is effective against waterborne bacterial pathogens, but not effective against viruses (poliovirus, rotavirus, norovirus, viral agents giving Hepatitis A and Hepatitis. E, and any number of viruses that can cause gastroenteritis).” Professor P S Datta, Project Director, Nuclear Research Laboratory, Indian Agricultural Research Institute, New Delhi feels that the filter will not be effective in areas where groundwater is highly contaminated with nitrate. He feels that no filter brand in India has come up till date with design to tackle nitrate contamination. Tata Chemicals claim that Swach can tackle six bacterial diseases caused due to poor quality of water.

In India there is no standard for water filter and hence there is no way to test whether the filters are effective under Indian conditions. “Swach compiles with the US Environmental Protection Agency (EPA) standard. We have filed 14 patents for the technology and the product ” explained Sastry. USEPA has standard for domestic water treatment device, which contains an antimicrobial (germ-killing) or bacteriostatic (slowing or inhibiting growth of germs) agent and not for lead, iron, arsenic and nitrates.

Design of the filter

The 560 mm tall Swach filter contains two parts. The upper part contains reservoir where the untreated water enters, the lower middle portion has a bulb to which the cartridge can be attached. Another reservoir is placed at the lower end, which collects clear water. The whole system acts on gravity and electricity or constant flow of water is not required. The stackability of two chambers reduces the height of the filter. The upper chamber can be easily cleaned. Depending on the quality of water about 3000 litres can be filtered after which the cartridge can be replaced. The flow rate of the filter is 3-4 litres per hour. “There is a fuse in the system which indicates time for cartridge change,” said Sastry. The cost of the cartridge would be somewhere around Rs. 299. The filter is in the launching stage right now. The Tata Chemicals plan to produce initially 1 million units a year from Haldia plant in West Bengal and then increase the production up to 3 million units within five years.

Comparable filters

This year B. Nagarajan and Dr. G.B. Jaiprakash Narain of MNM Jain Engineering College came up with a similar filter design using combination of Granular Activated Carbon (GAC) and nano silver colloid. The mixture is in the form of cartridge secured to the bottom of the top chamber. Nagarajan and Narain have also applied for a patent. Nagarajan is in Dubai for the marketing of this product. A popular brand by Kent also uses nano silver technology but has additionally attached Ultra Violet (UV) unit as UV is considered to be the most effective in removing microbial pathogens. Causes of almost 650 types of diseases that result from water borne pathogens could be eliminated by the simple implementation of nano silver disinfection methodology, views Narain.

Talking of the cost, Narain feels that their study has shown that nano silver disinfection process are available at a very economical price around Rs. 800. Tata’s Swach has also been priced between Rs. 749 to 999. Sujal was priced at Rs. 150 by TRDDC as it was using cheap RHA and the cost of the replaceable filter bed was only Rs. 25. The cartridge of the newly launched filter costs somewhere around Rs. 299. The increased cost is clearly due to the use of nano silver. Similarly the UV unit of Kent has increased its cost roughly to Rs. 8000 to 9000. Battery operated Pureit of Hindustan lever, which is closest to Swach in price range, uses carbon and chlorine mainly for purification.

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