Effect of electrode material and supporting electrolyte on the treatment of water containing Escherichia coli by electrocoagulation

Laboratory experiments were carried out to investigate the mechanisms of electrochemical disinfection of artificial wastewater contaminated by Escherichia coli culture (5 × 105 UFC/100 mL) using electrocoagulation. In order to go deeply into the mechanism of the process, the behaviors of two dissolved-type electrodes (ordinary steel and aluminum) and a non-dissolved-type (carbon graphite) electrode were compared. The ordinary steel electrode was found more efficient for E. coli cells destruction compared to aluminum and carbon graphite electrodes. In order to determine the most favorable condition for the treatment, the effect of various supporting electrolytes including, sodium chloride, sodium sulfate and sodium nitrate, was scrutinized. E. coli is inactivated by 5 log units for a charge loading of 37.30 F/m3 for sodium sulfate, 24.87 F/m3 for sodium nitrate and 12.43 F/m3 for sodium chloride. It thus appears that the most favorable supporting electrolyte type for this method of disinfection is sodium chloride, a fact which can be explained by the formation of disinfectant by-products such as chlorine dioxide, hypochlorite ions and perchlorate ions. From the results obtained, electrocoagulation applied to the elimination of E. coli proceeds through three combined effects: the electric field, the actions of oxidants electrogenerated during the process and the adsorption by the metallic hydroxides formed in solution.