Application of an electrochemical filter-press flowcell in an electrocoagulation-MBR system: Efficient membrane fouling mitigation

Abstract

In this study, we present efficient fouling mitigation of a pre-pilot Membrane Bio Reactor (MBR) for the treatment of synthetic wastewater through real integration with the Electrochemical Coagulation (EC) process by the application of a satellite filter-press electrochemical flowcell at the recirculation line of permeate produced by submerged hollow fiber membrane module. Flowcell was equipped with an aluminum anode and a steel cathode. Results indicated that the application of 5 volts was the optimum level for an EC-MBR for the removal of COD and fouling mitigation. 5 V-EC led to ca. 80 ± 3% COD removal, while MBR and 5 V-EC-MBR achieved almost 63 ± 4 and > 99% COD removal after 6 hr HRT, respectively. Moreover, the optimum 5 V-EC-MBR extended the membrane operational time by ca. 35 days in comparison with MBR. The formation of large microorganism flocs/more porous sludge cake layer along with the entrapment of Extracellular Polymeric Substances (EPS), were found as major mechanisms influencing the fouling mitigation. Dynamic Light Scattering (DLS) resulted in mean particle size (MPS)/zeta potential (ZP) values of − 5 ± 2.3/89 and − 60 ± 3/12 µm/mV for mixed liquor sludge flocs of 5 V-EC-MBR and MBR respectively, while colloidal re-stabilization (change in the sign of ZP and reduced MPS) was observed when applying larger voltages than 5 V. The presence and the reduction of EPS were verified using Fourier Transform InfraRed (FTIR) and fluorescence Emission Excitation Matrix (EEM). The results of this study pave the way for future techno-economic evaluations of continuous pilot EC-MBR equipped with multiple electrochemical flowcells for the treatment of real wastewater.