Small approach, big benefit

Nanotechnologies offer an economical way to make water potable

Published: Sunday 15 October 2006

Down to EarthDown to Earth Today, as many as 20 countries are classified as 'water scarce', based on their current sources of renewable fresh water vis--vis demand. This number is going to rise to 34 by 2025. Also, quality of drinking water is falling due to the increasing presence of pathogens. About half the people in developing countries are exposed to contaminated water

Down to Earth Globally, 1.1 billion people lack access to basic water supply and 2.6 billion lack access to basic sanitation. About 4 billion cases of diarrhoea occur every year, claiming nearly 2.2 million lives. Almost 90 per cent victims are children under five, which means diarrhoea kills 4,500 children a day, or one child every 20 seconds

Down to Earth To purify water, nanofiltration technologies have emerged as an option that is cheaper than most existing water cleaning technologies in terms of efficiency, maintenance and energy required to operate them. Besides, these technologies do not require the use of any chemicals

Down to Earth Conventional filters (such as sand filters) cannot remove dissolved salts, like arsenates, and some soluble inorganic and organic substances and bacteria. But nanofilters and nanomembranes have a real chance of removing bacteria, protozoa, viruses, and heavy metals like arsenic, mercury, lead, chromate, cadmium, and many harmful salts. However, nanomembrane technologies are costly compared to conventional methods. A conventional filtration plant can be set up at 70 per cent of the cost of a nanomembrane plant

Down to EarthDown to Earth Advanced mechanical filtration like diatom filtering and reverse osmosis can perform on the nanometre scale. But diatom filtering cannot remove chemical impurities due to large sizes of pores while reverse osmosis wastes 60-87 per cent of water and is slow

Down to Earth Nanofiltration membrane technology is widely used to remove dissolved salts from salty water, remove micropollutants, soften water and treating wastewater. In Chennai, energy costs in desalination is about Rs 50 per 1,000 litres of water. Nanofiltration processes can bring down the energy required for desalination by 20-30 per cent. Besides, this technology selectively rejects substances in water, thereby enabling the retention of nutrients like calcium

Down to Earth Nanofilters can remove up to 99 per cent of ammonia from contaminated waterways and sewage outflows. This allows the water to be recycled while the ammonia removed can be re-used as fertiliser. Nanofilter membranes, however, cannot satisfactorily remove certain ions such as those of nitrate and fluoride from water

Down to Earth Poor people in the developing world spend up to 25 per cent of their real income to have access to clean water. A fusion of conventional and nano-science based technologies can ensure safe water without any additional cost

Down to Earth Simple and affordable water treatment/filtration methods and materials, when suitably treated or impregnated with nanotechnology-based methods could filter more effectively and increase health benefits. For instance, four layers of an old sari can produce a nanoscale 30 mm mesh that can remove up to 99 per cent of cholera bacteria from water

Source: Nanotechnology,
Water and Development by the Meridian Institute,
Washington and Colorado,
Click here for Nano Water Final Paper>>

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