IICT finds a cost-effective answer to water purifiers

HYDERABAD:Scientists at Indian Institute of Chemical Technology(IICT) have designed hollow membranes which purify drinking water efficiently without causing any decrease in the mineral levels in water. They claim that once their product is commercialised, it will prove more cost-effective than present water purifying devices used at homes. The membranes look like thin plastic wires as they are made of polyethersulphone, a synthetic material.

'RO knocks off minerals from piped drinking water'

"Many people buy Reverse Osmosis (RO) water purifier without knowing the fact that RO purifiers should be used only if they rely on groundwater for drinking purpose.

As most of the people are now getting piped water supply from rivers, RO should not be used, as it knocks down essential minerals from water. Consuming such water has a negative impact on physical as well as mental health," Dr S Sridhar, head of Membrane Separations Group at IICT said.

The piped drinking water supplied by municipality has Total Dissolved Solids (TDS), which consist of minerals like Magnesium, Calcium, Sodium, Potassium and Phosphorous that are essential for the human body to stay fit.

As per the Bureau of Indian Standards (BIS), TDS levels till 500 mg/litre and usually piped water supply has TDS in the acceptable standards.

When this water is purified through reverse osmosis, the TDS levels fall down to less than 20 mg/litre. This results in drastic reduction of the essential



minerals in water.

However, if groundwater is being used for drinking, then RO purifier can be used as the TDS levels in groundwater are much higher than acceptable limits.

How it works

"The hollow membrane has pores which are as small as 0.001 microns. When water passes through this membrane, various contaminants like bacteria, virus, suspended solids, and colloidal silica that are larger than the pore size are filtered, thus giving out pure water. The essential minerals dissolved in water are of very small size and they do not get filtered and stay in the water thus maintaining good levels of TDS," Dr Sridhar says.

"Problem with RO purifier is that it removes essential minerals. In the UV purifier while the microbes are killed, their bodies continue to remain in water. In water purifiers that use charcoal, microbes are not killed." "Therefore the membranes are better as they remove the microbes and other contaminants completely, keeping minerals intact in the water," Dr Sridhar further added.

Electricity not required

If water purifiers for usage at home are made of the hollow membranes, they will not even require electricity. Dr Sridhar said that RO water purifiers require more than 100 psi pressure for which power has to be used, whereas the purifier using hollow membrane would require just around 15 psi which can be achieved if the water to be let into the purifier is coming from an overhead tank.