This study compared and evaluated the performance of a conventional membrane bioreactor (MBR) and a novel reciprocation MBR (rMBR) which used mechanical membrane reciprocation in place of membrane air scouring in pilot-scale tests. Each system was independently operated for 280 days at a local wastewater treatment plant for a parallel assessment of operating performance. The rMBR was found to be more effective than the MBR with regard to operating performance and energy consumption. Inertial forces created by the reciprocating motion shook foulants from the membrane surface. In addition, because of the looseness of the fibers, they moved relative to each other during reciprocation thus preventing sludge clogging inside the fiber bundle. Because the rMBR does not use aeration for membrane cleaning, the membrane tank in the rMBR maintained anoxic conditions, allowing endogenous denitrification in the membrane tank. The rMBR permeate contained an average of 1.7 mg/L total nitrogen (TN) with less than 1 mg/L NO3-N, while the TN concentration in the MBR permeate averaged 5 mg/L with 3.5 mg/L NO3-N. The specific energy consumption for membrane reciprocation in the rMBR was 0.064 kWh/m3, while that for air scouring in the MBR was 0.19 kWh/m3.

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