Review and analysis of defluoridation of drinking water by electrocoagulation

Excess fluoride in water and food is associated with dental and skeletal fluorosis and affects several parts of the world. Electrocoagulation is a potential method for removal of fluoride from drinking water. The aim of this paper was to review and analyse electrocoagulation-based defluoridation studies. Several factors are known to impact defluoridation efficiency and are discussed in detail in this paper. Major factors include: types of reactors and their operating parameters such as current or voltage; contact time; electrodes materials, configuration, spacing and shape; feed water composition; solution chemistry including pH, conductivity and competing ions. In general, highest removal efficiencies were observed in batch reactors while continuous-flow reactors showed greater variability in performance. Aluminium (Al) electrodes have been studied to a far greater extent than iron electrodes and comparative studies show better performance with aluminium. Highest removal efficiencies were observed with distilled or deionized water and lowest with synthetic water. This is mainly due to competition from other ions present in synthetic solutions which lowers removal efficiency for the contaminant of concern. Sludge and electrode analyses and various types of statistical and kinetic modelling are also reviewed. In conclusion, electrocoagulation can be successfully and economically applied for defluoridation of drinking water.