Improved anti-biofouling performance of CdS/g-C3N4/rGO modified membranes based on in situ visible light photocatalysis in anammox membrane bioreactor

Abstract

The photocatalyst CdS/g-C3N4/rGO, which can simultaneously degrade foulants and inactivate bacteria by illumination, is a promising anti-biofouling modification material for membranes. We tested a novel anti-biofouling strategy based on photocatalytic technology in situ in an anammox membrane bioreactor (MBR) assembled with 0.6 wt% CdS/g-C3N4/rGO modified membranes (M2). Compared with the pristine membrane M0, M2 was 9.4% more hydrophilic and had a 13.3% higher water permeability, along with substantially lower flux decline rates for model foulants and significantly higher inhibition rates against model bacteria (p < 0.05). By irradiation of waterproof lights during long-term operation of anammox MBRs, the mean fouling cycle of M2 was extended to 1.92 times that of M0 without compromising the total nitrogen removal efficiency (0.82 (M2) vs. 0.79 (M0), p > 0.05). Moreover, the quantities of organic foulants and total bacteria found on fouled M2 were, respectively, 53.9% and 77.5% lower than those on M0 (p < 0.05). We hypothesize that the reactive species (i.e., e–, h+, •OH) generated on M2 play the predominant role in foulants decomposition and the inactivation of attached bacteria. The novel CdS/g-C3N4/rGO modified membrane holds great promise for the application of visible-light photocatalysis for membrane fouling control in anammox MBRs.