Real brewery wastewater-driven selenate reduction in a granular activated carbon-enhanced AnMBR

Industrial selenium (Se)-laden wastewater often lacks sufficient biodegradable organic carbon to sustain heterotrophic Se oxyanion reduction, while its commonly occurring acidity and salinity pose additional challenges for the operation of anaerobic membrane bioreactors (AnMBRs). Real brewery wastewater, which is rich in readily biodegradable organic matter, may provide a low-cost source of electron donors while partially neutralising acidic Se-laden wastewater. This study evaluated this co-treatment strategy and the role of granular activated carbon (GAC) in maintaining AnMBR performance under salinity stress. Two parallel AnMBRs, one without GAC and the other with 2 g/L GAC, were fed a mixture of simulated acidic Se-laden wastewater and real brewery wastewater. Both reactors were operated without additional NaCl in Stage I and with 10 g/L NaCl in Stage II. Salinity had limited influence on total soluble Se removal, with average removal efficiencies exceeding 97% throughout both operational stages. The primary reduction product was biogenic crystalline hexagonal elemental Se. Salinity markedly inhibited COD removal and aggravated membrane fouling, whereas GAC addition reduced the membrane fouling rate by 19.7% and 28.3% in Stages I and II, respectively. In the GAC-amended reactor, Dechloromonas became predominant under saline conditions, while the relative abundances of serABC and napAB were elevated under non-saline and saline conditions, respectively. Overall, real brewery wastewater served as an effective waste-derived electron donor for Se-laden wastewater treatment, while GAC effectively mitigated membrane fouling in the AnMBR.