Effect of current density on the efficiency of a membrane electro-bioreactor for removal of micropollutants and phosphorus, and reduction of fouling: A pilot plant case study

Abstract

Submerged membrane bioreactors (SMBR) are widely known for their advantages in the field of wastewater treatment. However, despite the significant technological advances in recent decades, membrane fouling remains one of the major concerns for its efficient application. Recent studies, carried out with synthetic wastewater, show that the integration of electrochemical processes as electrocoagulation with membranes technologies provides promising advantages. This research focuses on the performance of a pilot-scale membrane electro-bioreactor (SMEBR) treating real wastewater with an average organic loading rate of 0.91 ± 0.44 mg/L COD from a municipal wastewater treatment plant). Current densities of 5, 10, and 15 A/m2 (charge loading of 214.17, 428.34 and 642.42 mA m−3·h respectively) and exposure time of 5′ON/10′OFF were applied to compare the efficiency of the SMEBR system versus the SMBR. The removal efficiencies of COD, nutrients (total nitrogen and total phosphorus) and 10 selected micropollutants (8 pharmaceuticals and 2 pesticides) were studied. The results showed that the SMEBR system improved the treated effluent quality in comparison with the SMBR, mainly regarding phosphorus, increasing its elimination by an average of 34.6%, and the micropollutants acetaminophen, clarithromycin and carbamazepine, which presented an average increase in the removal rates of 19%, 43% and 28%, respectively, comparing with those obtained in the SMBR. The optimal operational conditions were obtained when a current density of 5/A/m2 was applied. At this stage, the SMEBR showed a significant reduction in the membrane fouling, achieving reductions rates in transmembrane pressure and extracellular polymeric substances of 72.8% and 55.5%, respectively.