The National Environmental Engineering Research Institute (NEERI) has developed an indigenous and economically viable process with domestic and community applications to reduce high fluoride content in potable water.

According to an NEERI release, a chemo-defluoridation domestic unit consists of a steel container fitted with a sand filter at its bottom.

To reduce the fluoride content, a fluoride bearing water (30 L) is added in the container followed by dosing of the salts of calcium and phosphorous chemical coagulants with manual stirring.

When these salts are added to the fluoride-bearing water, they gradually get dissolved and precipitated absorbing fluoride from water, the release said.

The water along with the residue is then passed through the sand filter to get the treated water with fluoride less than the permissible limit of 1.0 mg/L, it said.

The process can be used for reduction of fluoride concentration from 5-8 mg/L to less than 1.0 mg/L (milligramme per litre). The process does not affect the palatability of water.

The release further said that efficiency of the filter is reduced roughly in a month due to settling of chemical precipitate on the sand filter which can then be manually cleaned by removing the top layer of the precipitate settled on the sand bed.

The cost of the household unit is about Rs 2000 and the treatment cost incurred is around 20 paisa per litre. The units are suitable for the small fluoride-affected villages where community water supply schemes are not economically feasible, the release said.

The NEERI, a constituent laboratory of the Council of Scientific & Industrial Research (CSIR) achieved the chemo-defluoridation of potable water with high fluoride content in collaboration with the Mumbai-based Rajeev Gandhi Science and Technology Commission.

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