Nanotechnologies offer an economical way to make water potable
 
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
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
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
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
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
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
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
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
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, USA; Click here for Nano Water Final Paper>> |
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