Exploring the potential of curcumin for control of N-acyl homoserine lactone-mediated biofouling in membrane bioreactors for wastewater treatment

Abstract

Biofouling remains a critical issue in membrane bioreactors (MBRs) for wastewater treatment. Thus, exploring novel approaches for biofouling inhibition is of crucial importance. Here, effects of curcumin incorporation in MBR-activated sludge in terms of permeate quality, extracellular polymeric substance (EPS) concentration, an increase in transmembrane pressure (TMP), and N-acyl homoserine lactone inhibition in the initial stage of treatment were investigated. Results showed that TMP of the test MBR (with curcumin) reached a critical level of 40 kPa after 22 days compared to 3 days for the control MBR (without curcumin). Chemical oxygen demand removal efficiencies from the control and test bioreactors permeate were 99% and 97%, respectively. Additionally, total phosphorus and nitrogen removal from both the bioreactors were almost 99%. Quorum sensing inhibition bioassay of MBR-activated sludge suggests that curcumin addition results in inhibition of short-chain AHLs. EPS analysis of the MBR-activated sludge showed that curcumin incorporation led to 14% lower EPS content than that found in the control bioreactor. Confocal microscopy revealed that the lower membrane biofouling in the curcumin-incorporated MBR occurred because of lower biofilm surface coverage (12% for test vs. 82% for control MBR) and average thickness (0.2 μm for test vs. 1.2 μm for control MBR). Field emission scanning electron microscopy images further confirmed the effect of curcumin on biofilm inhibition. The fouled membrane was characterized using Fourier transform infrared spectroscopy, with proteins found to be the major constituents. These results show that curcumin could be a promising agent for controlling quorum sensing-mediated membrane biofouling in MBRs for wastewater treatment.