A comprehensive study of electrochemical disinfection of water using direct and indirect oxidation processes

Abstract

The electrochemical disinfection (ECD) has achieved much attention due to its environmental compatibility, simplicity and production of oxidizing species. In the present study, the ECD of total coliform (TC) and fecal coliform (FC) was investigated with a focus on direct and indirect oxidation using a series of anodes (stainless steel (SS)/lead (Pb) O2 (SS/PbO2), stainless steel, titanium (Ti), platinum (Pt), graphite (GP) and Pb/PbO2). The influence of electrode material, current density (CD), charge passed, initial pH values, different concentrations of NaCl, TDS, electrical conductivity (EC) and energy consumption on process performance was examined. The amount of in situ generated active chlorine during the process under the optimal conditions for each anode was found to be effective in removal of bacterial. The disinfection system was very efficient in bacterial elimination in presence of 0.01 M NaCl. An increase in CD from 0.16 to 0.5 mA/cm2 resulted in a decrease more than 60% in log 10 bacterial load for all electrodes except Pt. Among anodes investigated, SS/PbO2 demonstrated the highest efficiency (complete inactivation) in 5 min by applying 0.01 M NaCl in current density of 0.5 mA/cm2 when charge passed was >15 C. The efficiency of the anodes in inactivation of TC and FC was in the order of SS/PbO2 > SS > Ti > Pt > GP > Pb/PbO2. In spite of the high efficiency of the electrochemical method in removing TC and FC, indirect oxidation has a higher efficiency due to the production of strong oxidants such as radical hydroxyl and active chlorine.