Recent Developments in Defluoridation of Drinking Water in India

Presence of high fluorides in groundwater has caused systemic fluorosis to become an endemic problem in many countries of the developing world, namely, India, Sri Lanka and many African nations. It is a conclusive fact that higher concentration of fluoride (beyond 1.5 mg/L) can cause teeth mottling and still higher concentrations may lead to different major health hazards including skeletal and neurological problems. The fluoride level in water in India ranges from 2 to 29 ppm, whereas the permissible level in drinking water according to WHO standard is 1.5 ppm and BIS 10500 permits only 1 ppm fluoride in drinking water. Various defluoridation techniques in India have been developed for maintaining the concentration of fluoride in water up to the permissible limit like Nalgonda Technique, reverse osmosis, activated alumina adsorption, Bio-F process, etc. Nalgonda Technique involves addition of Aluminium salts, lime and bleaching powder followed by rapid mixing, flocculation, sedimentation, filtration and disinfection and the acceptable limit of water of 1 mg/l has been achieved. Defluoridation using activated alumina as adsorbent is not cost-effective. Hence, development of community-based defluoridation unit is needed with a technique which is cost-effective, technologically simple in operation while being able to keep the fluoride level in permissible limit. The paper critically discusses the recent developments in various defluoridation processes, identifies the pertinent gaps in them and offers plausible solutions by summarizing the ongoing research at MNIT Jaipur in order to obviate these gaps through appropriate technological interventions.