New water filter removes fine microbes
-- cheap!

SCIENTISTS AT National Chemical Laboratory (NLC) in Pune, have come up with a water filter that can remove microbes from drinking water.

The filter has pores small enough to exclude virus and bacteria and yet allows passage of water on a slight tap pressure. Instead of electrical power, it runs on mechanical power which makes it suitable for village environment.

Bugs that causes typhoid, dysentery, tuberculosis, cholera, giardiasis, polio, hepatitis and encephalitis can be removed by the filter, according to B. D. Kulkarni of NLC who along with his team developed and patented the filter.

The cost of the membrane-treated water would be around 83 paise per litre and if the water is free from undissolved suspended particles, it can last upto three to four years, he said, adding that the system is self- cleansing too.

It is based on a technique called ultrafiltration (UF) that allows formation of pores smaller than the dimension of microbes.

The membrane was a successfully tested with Escherecha colibacteria and Picorniatype virus as well as with small molecules like albumin, casein and polythylene glycol.

Chlorine treatment - the commonest water treatment method - requires harsher condition and cannot remove spores and cysts completely.

Other methods such as ultra violet or ozone treatment, too have disadvantages as the remants carrying residual toxins remain in water.

On the contrary, the new UF technique only needs membrane replacement after every three to four years, he claimed.

The system consists of a mechanical pump that circulates water from the tank to the membrane at a given pressure. The feed water is passed through the membrane in a tangential direction so that large molecules do not block the pores. The technology is already being used in France and Japan.