Comprehensive treatment of urban wastewaters using electrochemical advanced oxidation process

Abstract

This study mainly focuses on the efficiency of anodic oxidation process (Ti/Sb-SnO₂/PbO₂ as anode and stainless steel as the cathode) in treating two different streams of urban wastewater, one from the influent of sequence batch reactor (WW1) and other from the effluent of constructed wetland (WW2). The effect of different operational parameters such as current density, hydraulic retention time, exposed electrode surface area, phosphorous, ammonia-nitrogen, nitrates, and coliform bacteria was studied. For an optimized current density of 30 mA/cm² and an electrode surface area of 30 cm², almost complete removal of COD and ammonia-nitrogen were achieved with both wastewaters (WW1 & WW2), while in case of phosphorous, 50% and 98% removal efficiencies were observed. Electrode deposition was analyzed using SEM-EDS and XRD, which confirms the presence of calcium and magnesium phosphates on the surface on the anode, which attributes to the phosphate removal. Electrochemical disinfection studies showed that complete inactivation of bacteria takes place within 30 min for WW1 and 60 min for WW2, and the cell morphological changes were studied using SEM analysis. Degradation of different micropollutants present in the wastewaters was evaluated with the aid of GC-MS. ICP - MS analysis confirmed that there was no leaching of lead from the anode surface, and the lead which is already present in the wastewater gets reduced to a permissible level, which further increases the treatment efficiency. Hence cleaner and comprehensive treatment of real urban wastewaters through anodic oxidation process was successfully demonstrated in this work.

Keywords: Electrochemical disinfection; Electrochemical oxidation; Removal of micropollutants; Removal of nutrients; Ti/Sb-SnO(2)/PbO(2)anode; Urban wastewater.