Treatment of canola-oil refinery effluent using electrochemical methods: A comparison between combined electrocoagulation + electrooxidation and electrochemical peroxidation methods

Abstract

A comparative study of combined electrocoagulation (EC) + electrooxidation (EO) and electrochemical peroxidation (ECP) treatment processes were carried out to treat canola oil refinery (COR) wastewaters. The effect of applied current density and operation time in the removal of organic pollutants were investigated and discussed. Total chemical oxygen demand (TCOD), soluble chemical oxygen demand (sCOD), total organic carbon (TOC), dissolved organic carbon (DOC) and total suspended solids (TSS) were measured. Using only EC process was found to be significantly successful in removing suspended and colloidal pollutants and could remove more than 90% TCOD and 80% of TOC at current densities between 0.91 and 13.66 mA cm−2. From the statistical model, the optimized conditions for TCOD at a current density of 7.61 mA cm−2 and TOC at 7.99 mA cm−2 under 40 min operation, validated to remove 93.45% and 94.5% respectively. However, the maximum removal of dissolved organic pollutants was relatively low in EC process and reported to be 75% for sCOD and 74% for DOC. Therefore, EC + EO process were run to increase the removal of sCOD and DOC to 99 and 95%, respectively. On the other hand, treatment using ECP process achieved a removal of sCOD and DOC between 77 and 86%. TSS were removed completely in both EC + EO and ECP processes. A statistical model was applied to compare the performance of two methods and found that the combined EC + EO process provided lightly better treatment compared to ECP method.