Removal of fluoride from water by using a coagulant (inorganic polymeric coagulant)

Excess fluoride (F) ion of drinking water is a major problem in many areas of India and causes harmful effects such as dental and skeletal fluorosis. The World Health Organization (WHO 2004) recommends an upper limit of 1.5 mg/L fluoride in drinking water, and the concentration of fluoride in groundwater has been found 10-20 times higher in many of the States in India. In this study, the performance of inorganic polymeric coagulant (IPC) named as IPC-23, IPC-13, IPC-17, and alum for fluoride removal from drinking water was investigated. The amount of IPC was decided according to the Al₂O₃ amount present in the alum dose recommended in the batch Nalgonda defluoridation technique. The effects of coagulant dosage (IPC) at different pH and initial concentrations of fluoride on fluoride removal have been studied. The synthetic sample having a fluoride concentration of 2 to 6 mg/L was treated at the optimized dosage and residual fluoride was reduced to 1.0 to 1.2 ppm with IPC-17. Residual aluminum in treated water was well within WHO norms (< 200 μg/L) for drinking water. Optimum pH for fluoride removal was 6.5, and there was deterioration in the performance of IPC at both lower and higher pH.