Performance analysis of a combined system of membrane bioreactor and worm reactor: Wastewater treatment, sludge reduction and membrane fouling

A new process that combined a membrane bioreactor (S-MBR) and a novel worm reactor was proposed in this study. The combined system indicated excellent sludge reduction efficiency, wastewater treatment performance and membrane permeability. The sludge reduction percentage of the combined system was about 1.9 times higher than that of the conventional MBR. The chemical oxygen demand (COD) discharge rate in the combined system was only one fourth of that in the conventional MBR, indicating that the COD was removed more thoroughly. Low extracellular polymeric substances level (60–75 μg/mg), low filamentous bacteria level, narrow floc size distribution (distribution spread index of 0.91) and high roundness (0.80 ± 0.10) were observed in the S-MBR sludge. Deposited by this modified sludge, a fouling layer with smaller thickness, larger porosity and less proteins and polysaccharides accumulation was formed in the S-MBR, demonstrating that the combined system was able to alleviate membrane fouling.