Assessment of denitrification using electrocoagulation process

Abstract

AbstractThe objectives were to study the applicability of electrocoagulation (EC) for the denitrification of drinking water and to determine the main mechanisms of pollution removal. Electrolysis in the intensiostatic mode was applied to a synthetic water representative of potable water in which the concentration of nitrate ions was varied up to 200 mg/L. The respective influences of process parameters, initial concentration of nitrates, and initial pH were investigated. Experimental results show that EC removes efficiently nitrates, following first‐order kinetics. A two‐step mechanism was established: it consisted of the electroreduction of nitrates into ammonium on the cathode, followed by the adsorption of ammonium on the precipitated oxyhydroxides. Adsorption exhibited a zero‐order mechanism. The rates of the two mechanisms were proportional to electrical charge loading and to the total amount of aluminum released in water, as current did not modify significantly the surface area of precipitates. However, adsorption was impaired by the increase of pH resulting from the electroreduction of nitrates, whereas the electrochemical step was insensitive to pH. While the electroreduction of nitrates is known to be far more expensive than biological denitrification, aluminum hydroxides formed during EC present interesting adsorption properties for ammonium removal.