IISc team says RO units in Karnataka villages waste more water and pollute source

Nearly 13,000 RO water purification units installed by Karnataka government to get rid of fluoride and uranium contamination from ground water before drinking, don’t provide an “eco-friendly and sustainable solution” to a problem dogging the state for long because such units generate three times more waste water heavily loaded with the same two contaminants that go back to the source.

After analysing the usefulness of village RO plants, researchers at the Divecha Centre for Climate Change at Indian Institute of Science, Bengaluru said better maintenance would improve their performance, but continuing with the unit would mean wastage of 3-4 times water each of them produce, which is a matter of concern in districts which are deficient in groundwater resources. In addition, the waste water leads to further contamination of the feed water.

“Proper monitoring and maintenance of the (RO unit) membranes can help optimum performance. But this will not help bring down the wastage of 3 to 4 times the water they produce and also pollution the waste water induces in the environment,” team member and veteran IISc scientist R Srinivasan told DH.

There are more than 14,000 villages in eastern Karnataka with 80 per cent of them relying on ground water for drinking. But not only the water is heavily contaminated with fluoride, in 2020 occurrences of uranium in high concentration were found at many sites. There is also high arsenic content in part of east Karnataka.

To improve the water quality, the Department of Rural Water Supply has installed 12,911 RO (reverse osmosis) based water purification units, 80 per cent of which are in eastern Karnataka.

In order to examine the RO units’ performance and their desirability on a long run, the IISc researchers partnering with scientists from Mangalore University and Geosciences Environment in Toulouse analysed the feed water, purified water and waste water coming out of such units in 15 villages in four water critical districts – Chikkaballapur, Chitradurga, Kolar and Tumkuru.

Out of the 15 units investigated, only two were found performing satisfactorily in removing fluorides and uranium. While the performance of others can be improved by regular cleaning or replacing the membrane, the wastewater carry a higher percentage of the same two contaminants.

“We observed that the concentrate (waste water) is discharged in open channels or drains and seeps into the ground, ultimately recharging the groundwater and further contaminating it. There are also instances where the rejected water is being used for recharging the groundwater. Management of concentrate from the RO units, as practised at present, is unsatisfactory and not eco-friendly,” the team reported in a recent issue of the journal Current Science.

Srinivasan said the government should consider the use of harvesting roof water and sourcing water from perennial lakes (tanks) in the vicinity of affected villages. "The other possibility is to condense water from the atmosphere, feasibility of which in the interior parts of the mainland needs to be studied."

Another key problem was some of the RO units produced purified water with a very low concentration of fluoride, which could lead to dental caries upon extended periods of consumption of such water.

“The WHO and Bureau of Indian standards give permissible limits for the various elements in drinking water. For fluoride, the permissible limit in drinking water is in the range 0.5 to 1.5 mg/l. Fluoride concentration below 0.5 mg/l (generated by some of the RO units) leads to dental caries.” Srinivasan said.

“While addressing the problem of dental fluorosis through the consumption of RO purified water, one may head towards a condition that promotes dental caries. It does not appear to be a good bargain.”