Fluoride in groundwater: evaluation of removal methods

In the wake of widespread fluoride occurrence in groundwater, the incidence of endemic fluorosis across the country is alarming. In the year 2009, the Central Ground Water Board and Rajiv Gandhi National Drinking Water Mission reported 218 and 229 districts to be affected with high fluoride content in groundwater, particularly in the states of Assam, Andhra Pradesh, Gujarat and Rajasthan with over 50% districts affected. This has of late become a critical hazard giving rise to both dental and skeletal fluorosis, such as mottled teeth (brown / yellow stained, discolored and chalky white patches on teeth), sporadic pain on joints, osteosclerosis of pelvis and vertebral spine, crippling deformities, etc. The removal of excess fluoride is cumbersome and an expensive process. At present, methods being generally used to treat or remove fluorides include chemical precipitation with alum and lime, activated alumina, ion exchange process, electro-dialysis and reverse osmosis. In view of the above, the Paper highlights the various methods of treatment and their advantages and disadvantages in detail, and recommends suitable treatment technologies for fluoride removal from groundwater to bring down the fluoride level to less than 1.0 mg/L desirable limit and 1.5 mg/L permissible limit prescribed by IS 10500:2012, the WHO recommended permissible limit of 1.5 mg/L of fluoride concentration in drinking water.