Fluoride Contamination in Groundwater: A Pilot Study on Dug Well Recharge System for In situ Mitigation

Abstract

Dissolved ions concentration in groundwater beyond the recommended limits is a major problem as they make the water unsuitable for drinking purpose. Fluorine commonly found in certain rocks is released into groundwater due to the processes of rock–water interaction. This leads to increase in the concentration of fluoride in groundwater which is a major problem in several parts of the world including India. Presence of fluoride beyond the prescribed limits causes health problems to humans due to prolonged consumption of water, which is common in many parts of India. Dental and skeletal fluorosis is observed due to prolonged drinking of water with fluoride concentration above 1.5 mg/l. The objective of the study is to know how fluoride get released from the host rock and spot out suitable location for installing a dug well recharge system to decrease the fluoride concentration in groundwater. Several methodologies exist for in situ or exsitu removal of fluoride from groundwater. Exsitu methods can be enforced at community level or even at household level for the reduction of fluoride before its consumption, through ion exchange, reverse osmosis, adsorption, electrodialysis, coagulation, Nalgonda technique, electrodialysis, coagulation, precipitation, etc. Even artificial recharging structures can also be built in suitable location for diluting fluorite concentration in groundwater. Rainwater harvesting is also found effective to reduce the fluoride concentration of groundwater in existing wells. A pilot study was carried out by construction of a dug well recharge system in Dharmapuri district, Tamil Nadu, India. The study successfully demonstrated the applicability of dug well recharge system at a carefully selected site based on the systematic long-term hydrogeochemical studies to solve the problem of fluoride contamination affecting millions of rural people.