QUORUM QUENCHING BASED ANTI-BIOFOULING MECHANISM IN A SEMI-PILOT SCALE MBR TREATING REAL WASTEWATER

Abstract

Biofouling, due to extracellular polymeric substances and microbial cells, on the membrane surface is a persistent problem in the widespread application of Membrane Bioreactor (MBR) technology. It has already been revealed that many wastewater bacteria rely on N -acyl homoserine lactones (AHLs) mediated quorum sensing via cell to cell communication to synchronize their activities essential for biofilm formation by releasing soluble EPS into the environment. Recently, use of bacterial quorum quenching i.e. disruption of quorum sensing, to control the biofilm formation, by mineralizing the AHLs has successfully been reported using synthetic wastewater. In the present study, biofouling control by using the Rhodococcus sp. entrapped in "W" beads in MBR was investigated. Two parallel semi-pilot scale MBRs i.e., QQ-MBR with W-beads and C-MBR with vacant W-beads, were monitored at 0.5% effective volume of the bioreactor using real wastewater. QQ-MBR showed an enhanced anti-biofouling capability i.e. 4 times longer filtration cycle to reach trans-membrane pressure (TMP) of 30kPa, as compared to C-MBR. Less AHLs concentration in the QQ-MBR extract than the C-MBR was observed using high performance liquid chromatography (HPLC) technique. Less soluble EPS concentration in the QQ-MBR (32 mg/L) than in the C-MBR (57 mg/L) along with AHLs degradation reduced the formation of mature and dense biofilm till the 70 d of operation. Moreover, increase in the QQ-MBR sludge dewaterability in terms of capillary suction time (CST) and decrease in the sludge cake compressibility in terms of specific cake resistance (SCR) was found. Removal efficiency of both MBRs in terms of organics and nutrients were found to be comparable with good effluent quality. Study confirms the successful application of quorum quenching as anti-biofouling strategy in MBR treating real domestic wastewater and potential use for pilot and full scale applications.