Impact of feeding regimes on the performance of anaerobic sequencing batch membrane bioreactor treating wastewater from an urban drain

This work evaluated an anaerobic sequencing batch membrane bioreactor (AnSBR-MBR) equipped with waste-based ceramic membranes for treating low-strength real drain wastewater. Two feeding regimes, viz. settled feed (Phase 1) and mixed feed (Phase 2) were compared. The biological performance (chemical oxygen demand (COD) and phosphate (PO43-) removal) and filtration performance (total suspended solids (TSS) removal and membrane fouling) were investigated. The reactor characteristics in terms of solids content, sludge settling behaviour, and extracellular polymeric substances (EPS) were also assessed. In Phase 1, the settled feed (with the absence of particulate organic matter) resulted in low volatile suspended solids (VSS; 0.23 ± 0.15 g/L), causing low COD removal (28.38 ± 8.14%). In the mixed feed regime in Phase 2, VSS increased (1.82 ± 0.60 g/L) due to the organic content in the particulate matter, which gave microorganisms additional food, resulting in increased COD removal (47.42 ± 2.81%); this phase was also characterised by lower membrane fouling because of the lower EPS content. Marginally higher TSS removal was obtained as well in Phase 2 (96.72 ± 3.26%) than in Phase 1 (90.48 ± 8.14%). This work demonstrates that AnSBR-MBR performance is superior with mixed drain wastewater containing suspended solids and thus pre-settling is not recommended.