Application of electrocoagulation: issues with community-level defluoridation

Abstract

Fluoride contamination in groundwater causes major health problem due to fluorosis (skeletal and dental). This study focused on the development of an electrocoagulation-assisted fluoride removal system where activated alumina can be used as a downstream polishing unit for additional removal of fluoride. Laboratory experiments showed rapid and effective removal of fluoride at about 200 C/l of electro-charge loading from contaminated water with 2.1 mg/l of fluoride. Nalagola village of West Bengal in India, where most of the available drinking water sources were contaminated with excess fluoride, was selected for the installation of the defluoridation unit. The electrocoagulation unit along with the downstream sand filter was able to decrease the fluoride level below 1.0 mg/l, and therefore, the activated alumina column was kept as standby. However, in case the electrocoagulation system malfunctions due to passivation or disruption of power supply, the alumina column will be put to use to treat the water to the desired extent. Higher fluoride content in the contaminated water will, however, require the downstream alumina column as the polishing unit for adequate removal of fluoride. It was observed that deposits of aluminum and calcium oxides/hydroxides on the electrode surfaces caused passivation of the electrodes and regular reversal of polarity helped to avoid passivation to a large extent. The community-based defluoridation unit of capacity 600 l/h is serving about 320 families. The water committee formed by the beneficiaries are collecting water tariff from each family, and the fund is helping in operation of the filter for the last 33 months.