Performance and membrane fouling in a novel algal-bacterial aerobic granular sludge (ABGS)–membrane bioreactor: Effect of ABGS size

Abstract

A novel algal bacterial aerobic granular sludge (ABGS)–membrane bioreactor (MBR) for wastewater reuse was established to improve the pollutants removal and mitigate membrane fouling. Six ABGS particle sizes (< 0.60, 0.60–0.85, 0.85–1.18, 1.18–1.70, 1.70–2.00, and > 2.00 mm) were adopted to investigate their influence on the ABGS-MBR system. An optimal size (0.85–1.18 mm) was identified, which had the longest operation time (141 days) and the lowest fouling resistance (6.41 × 1011 m−1). This was possibly due to that it formed a loose cake layer and produced the content of lowest extracellular polymeric substances (EPS). For ABGS particles <0.85 mm, the small granules and flocculent sludge formed a dense fouling layer on the membrane surface, which quickly increased the fouling resistances. ABGS particles >1.18 mm secreted more EPS and formed more disintegration products of ABGS, which could enter the membrane pores through the loose cake layer, thereby causing severe membrane pore blocking. Moreover, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory showed that ABGS particle size of 0.85–1.18 mm led to the optimal antifouling performance owing to the highest energy barrier. This study elucidates the influence of ABGS particle size on membrane fouling mechanisms and provides a novel strategy to mitigate membrane fouling.