Performance of MBR in treating tomato paste processing wastewater: A comparison of aerobic granules with activated sludge

Membrane bioreactor technology has become increasingly popular for treating various industry wastewater because of its high treatment efficiency, small footprint and excellent effluent quality. Performance of aerobic granules (AG) and activated sludge (AS)-based submerged membrane bioreactors implemented for tomato paste processing wastewater treatment was investigated and compared in this work, particularly in terms of membrane fouling and microbial community structure at different conditions. The results revealed that the chemical oxygen demand in the aerobic granular system showed slightly better removal efficiencies (92%) than those in the activated sludge system (90%) while the performance of activated sludge membrane bioreactor is more stable over the experimental test time. According to the total filtration resistance, the aerobic granular system demonstrated superiority initially, while the activated sludge system performed better with disintegrated aerobic granules. Indeed, the membrane fouling resulted from disintegrated aerobic granules was most serious, which was further confirmed by atomic force microscopy. In addition, the cleaning efficiency was 96% in the aerobic granular system, which was nearly 10% higher than that of the activated sludge system. The difference between the bacterial community structures in both systems was analyzed, and the dominant bacteria were transformed into Rhodocyclaceae and ASSO-13 at the family level indicating that consortia gradually became the predominant bacteria in the tomato paste processing wastewater.