Impact of quorum quenching bacteria on biofouling retardation in submerged membrane bioreactor (SMBR)

Abstract

Membrane biofouling is a critical operational problem that hinders the rapid commercialization of MBRs. Quorum quenching (QQ) has been investigated widely to control membrane biofouling and is accepted as a promising anti-fouling strategy. Various QQ strategies based on bacterial and enzymatic agents have been identified and applied successfully. Whereas, this study aimed to compare indigenously isolated QQ strain i.e., Enterobacter cloaca with well reported Rhodococcus sp. BH4. Both bacterial species were immobilized in polymeric beads and introduced to two different MBRs keeping the overall beads to volume ratio as 1%. Efficiencies of these strains were monitored in terms of prolonging the membrane filtration cycle of MBR, release of extra-cellular polymeric substances, membrane resistivity measurements and mineralization of signal molecules and permeate quality. Indigenous strain (Enterobacter cloaca) was added to QQ-MBRE while Rhodococcus sp. BH4 was introduced to QQ-MBRR. QQ bacterial embedded beads showed enhanced filtration cycles up to 1.4 and 2.3 times for QQ-MBRE and QQ-MBRR respectively as compared to control MBR (C-MBR). Soluble EPS concentration of 52 mg/L was observed in C-MBR while significantly lower EPS concentration of 20 and 10 mg/L was witnessed in QQ-MBRE and QQ-MBRR, respectively. Therefore, substantial reduction in biofouling showed the effectiveness of indigenous strain.