ROUNDWATER DEFLUORIDATION WITH ELECTROCOAGULATION AND ELECTRODIALYSIS TECHNIQUES

Fluoride has been detected in groundwater in many places throughout the world and its concentration is often higher than the WHO standard of 1.5 mg/L. Too much fluoride can cause teeth and skeletal issues in the body and inhibit local economic growth. Fluoride concentration in the local groundwater in the Rajasthan region of India is above 5 mg/L and poses significant health risks to local people. Electrocoagulation and electrodialysis have been used for fluoride removal but information on their application for cost-effective removal of fluoride in groundwater is still limited. The aim of this study was to develop and evaluate cost-effective defluoridation systems to remove fluoride from 5 mg/L to below 1 mg/L in the groundwater. Multiple electrocoagulation reactors were fabricated with an aluminum anode and copper/steel cathode. Fluoride concentrations decreased from 5 mg/L to below 1 mg/L within 2 hours of electrocoagulation under an applied potential of 8 V. Under a lower applied potential of 5 V, fluoride concentration was reduced to below 1 mg/L after 6 hours 30 minutes and further reduced to 0.191 mg/L after 9 hours 30 minutes. Our results showed that higher voltage led to higher removal efficiency at a cost of higher energy consumption. The results showed that aluminum alloy used as the anode released impurities into the water during electrocoagulation and could affect fluoride removal efficiency. In addition, synthesized groundwater with different hardness levels was prepared to simulate water quality in the groundwater in the Rajasthan region of India. The results showed that high hardness inhibited fluoride removal efficiency. An electrodialysis reactor was tested as well on the removal performance of anions, including fluoride and chloride. Fluoride concentration after one hour of electrodialysis did not decrease below 1 mg/L but showed a promising trend for effective fluoride removal. However, cation permeable membrane and anion permeable membrane are relatively expensive and could affect the overall cost-effectiveness of fluoride removal with electrodialysis. These results showed that both electrocoagulation and electrodialysis were effective in removing fluoride from groundwater. Their long-term performance and overall cost-effectiveness need further investigation.