Evaluation of a novel physical cleaning strategy based on HF membrane rotation during the backwashing/relaxation phases for anaerobic submerged MBR

Abstract

A novel physical cleaning strategy based on membrane rotation was investigated in an anaerobic membrane bioreactor treating wastewater. This strategy was proposed to improve the fouling removal effectiveness of the traditional physical cleaning techniques (such as backwashing and relaxation) by the shear-enhanced conditions associated with the rotation. The effectiveness of this strategy has been investigated in a bench filtration unit during short-term tests and also compared to the conventional mode with gas scouring. Based on the resistances-in-series approach, the external residual fouling has been identified as the main factor determining the process productivity. The contribution of this type of fouling obtained with the rotating membrane was lower than with the gas scouring application (56–18% versus 60–53%, respectively). Other operational parameters such as the transmembrane pressure set-point for cleaning initiation and the backwashing time have also showed a significant influence on external fouling re-dispersion. A long-term test revealed the sustainability of the operation during more than 400 h, achieving a stable net permeate flux of 6.7 L/h m 2 when the rotating speed was fixed in 340 rpm.