Assessment of electrolytic process for water defluoridation

Abstract

Excessive intake of fluoride causes fluorosis, a disease affecting the multiple tissues, organs and systems in the body. Higher concentrations of fluoride in groundwater are a global problem, occurring in at least 25 countries across the globe and affecting millions of people. It is a threat to millions in the country as it ultimately leads to crippled and vegetative life. National Environmental Engineering research Institute (CSIR-NEERI), India has developed Electrolytic Defluoridation (EDF) technique for the treatment of excessive fluoride in water sources.  The process is based on the principle of electrolysis by passing Direct Current (DC) through aluminium plate electrodes placed in fluoride containing water. During the process, aluminium plate connected to anode dissolves and form polyhydroxy aluminium species that remove fluoride in water by complex formation followed by adsorption and removal by settling. The effects of operational parameters such as initial pH, current intensity, influent fluoride concentration, flow rate and residual aluminium were considered. The pH value was found to be an important variable that affected fluoride removal significantly. The optimal influent pH range is 6.0–7.0 at which effective defluoridation was achieved and optimum value was adopted as 6.5. It was found that EDF plants produce the treated water with fluoride less than 1 mg/L. It is revealed that current intensity has little effect on fluoride removal and the residence time requirement increases with the rise in initial fluoride concentration.

Keywords: Aluminium electrodes; electrolytic defluoridation; operational parameters