Bioelectrochemical cell (BeCC) integrated with granular activated carbon (GAC) in treating spent caustic wastewater: Effects of mixed liquor suspended solid (MLSS)

Abstract

The study present the feasibility of a bioelectrochemical cell (BeCC) integrated with Granular Activated Carbon (GAC) as the bacterial attachment medium in treating spent caustic wastewater. BeCC is a bioelectrochemical reactor that uses activated sludge for substrate degradation while also capable in energy recovery. Unlike the general MFC configuration, the BeCC reactor is cost effective as it was operated without a proton exchange membrane (PEM). Instead, a baffle is used to reduce the oxygen transfer to the other side of the reactor and the employment of the baffle has divide the reactor into hybrid of anoxic and aerobic conditions. Also, instead of using packed GAC, the BeCC was integrated with 10 g of suspended GAC in order to increase the surface area available for bacteria to attach. The study investigated the best operating MLSS for the system to treat spent caustic wastewater whereby the BeCC was tested at various MLSS of range within 2500 mg/L to 4000 mg/L and its performance in terms of Chemical Oxygen Demand (COD) and sulfide removal as well as it open circuit voltage (OCV) were evaluated throughout 30 days of operation. From the study, the highest COD removal of the system was 95.6% achieved at MLSS of 3500 mg/L whereas the highest sulfide removal was 87.1% achieved at MLSS of 3000 mg/L. The highest OCV was 413.7 mV achieved at MLSS of 3000 mg/L.