Membrane fouling amelioration through pseudo dead-end filtration coupled with transmembrane pressure (TMP) set-point control in an anaerobic membrane bioreactor for municipal wastewater treatment

Abstract

In this study, a novel gas sparging regime was applied, in which filtration was conducted without gas sparging to create a pseudo dead-end (DE) filtration cycle followed by membrane relaxation/backwashing for a short period of time with gas sparging until the TMP set-point was achieved. Compared with conventional continuous filtration and continuous gas sparging (CGS) modes and temporal pseudo DE filtration modes, this pseudo DE filtration coupled with TMP set-point control mode can achieve lower energy demand with sustainable membrane operation. The impacts of the TMP set-point value, imposed flux and physical cleaning process (membrane relaxation/backwash coupled with gas sparging) were evaluated. The result indicated that a moderate TMP set-point value (10–12 kPa) should be selected. Backwashing can significantly reduce the irreversible fouling and enhance the net permeate flux. However, when the TMP set-point value was higher (TMP_set = 14 kPa), severe cake layer consolidation occurred and no appreciable improvement of fouling control was observed even with backwashing coupled with gas sparging. The optimum condition can be established when the TMP set-point value was 12 kPa at a flux of 15 L m⁻² h⁻¹ in terms of a higher net flux and lower specific energy demand. Importantly, sustainable membrane operation can be achieved under pseudo DE filtration coupled with TMP set-point control mode with a low energy demand (0.09 kWh m⁻³) and low operational cost ($0.027 per m³), promoting energy neutral municipal wastewater treatment to be realized.