Dissolution of fluoride in groundwater: a water-rock interaction study

Fluoride-rich groundwater is well known in granite aquifers in India and th e world. Although its presence is necessary, chances of health risk become high if the fluoride concentration is more than the permissible limit of 1. 5 mg/l (World Health Organization, WHO) in drinking water. Fluoride mainly occurs in groundwater as a natural constituent. Results of a laboratory stu dy on water-rock interaction at normal temperature, pressure and different chemical conditions indicate that the specific conductivity, pH, Ca and HCO 3 are important chemical parameters for the dissolution of fluoride to grou ndwater from fluoride-rich minerals (e.g., fluorite). Experimental results indicate that an alkaline medium (pH=7.6 to 8.6), high HCO3 concentration ( ranging from 350-450 mg/l), and moderate specific conductivity (ranging fro m 750-1,750 muS/cm) are favourable for fluoride dissolution. No significant correlation existed between fluoride and CaHCO3.