Experimental Evaluation of a Novel Backflush Controller for Immersed Membrane Systems

Membrane backflush with air or permeate is commonly employed to reduce fouling in immersed micro- and ultrafiltration (MF/UF). Membrane plants traditionally rely on simple timer control automation to initiate periodic backflushes for membrane cleaning. In this study, a closed-loop (feedback) type backflush controller was evaluated experimentally with a bench-scale hollow fibre immersed MF/UF membrane - flocculation hybrid system.The controller showed an unexpected behaviour at low fouling rates, which was manifested in significantly varying filtration periods. The investigation identified the cause in the use of a constant stabilisation lag parameter. The role of this control parameter was to determine the reversible component of fouling in real-time, which is a difficult problem in transient flow conditions that characterise the start of filtration periods. The resulting error became significant at low fouling rates and impaired effective control.Based on this insight, we propose alternative, more robust control parameters, which can provide improved backwash control solutions for MF/UF membrane applications.