Combination of the Electro/Fe3+/peroxydisulfate (PDS) process with activated sludge culture for the degradation of sulfamethazine

Abstract

In this paper, the major factors affecting the degradation and the mineralization of sulfamethazine by Electro/Fe3+/peroxydisulfate (PDS) process (e.g. current density, PDS concentration, Fe3+ ions concentration and initial sulfamethazine (SMT) concentration) were evaluated. The relevance of this process as a pretreatment prior to activated sludge culture was also examined. Regarding the impact on SMT degradation and mineralization, the obtained results showed that they were significantly enhanced by increasing the current density and the PDS concentrations in the ranges 1–40mAcm−2 and from 1 to 10mM respectively; while they were negatively impacted by an increase of the initial SMT concentration and the Fe3+ concentration, from 0.18 to 0.36mM and from 1 to 4mM respectively. The optimal operating conditions were therefore 40mAcm−2 current density, 10mM PDS concentrations, 1mM Fe3+, and 0.18mM SMT. Indeed, under these conditions the degradation of SMT and its mineralization yield were 100% and 83% within 20min and 180min respectively. To ensure a significant residual organic content for activated sludge culture after Electro/Fe3+/PDS pre-treatment, the biodegradability test and the biological treatment were performed on a solution electrolyzed at 40mAcm−2, 10mM PDS concentrations, 1mM Fe3+, and 0.36mM SMT. Under these conditions the BOD5/COD ratio increased from 0.07 to 0.41 within 6h of electrolysis time. The subsequent biological treatment increased the mineralization yield to 86% after 30days, confirming the relevance of the proposed combined process.