Mitigation of membrane biofouling using quorum-quenching bacteria in a continuously operated membrane bioreactor

Abstract

Quorum-quenching (QQ) has become an attractive strategy for the mitigation of membrane biofouling known as biocake or biofilm. In this study, a QQ system, which exploited two QQ bacteria (Serratia sp. Z4 and Klebsiella sp. Q2) and γ-caprolactone (GCL), was established and used to effectively mitigate biofouling. This system could delay the increase in transmembrane pressure by half during a 40-day operation in a continuous membrane bioreactor (MBR) with low effluent chemical oxygen demand and ammonium nitrogen. GCL improved the biofouling-mitigation ability of the QQ bacteria without stimulating bacterial growth. The reduction in soluble microbial products was consistent with the delay in transmembrane pressure increase. Furthermore, soluble microbial products (SMP) in the reactors were significantly influenced by the QQ system, suggesting that SMP was important for the occurrence of biofouling. Microbial community analysis showed that the relative abundance of some main genera was not greatly influenced by the QQ system. The two most abundant genera of quorum sensing (QS)-related bacteria found in the sludge mixture were Alicycliphilus and Thauera. The results indicated that a QQ strategy based on the disturbance of QS among the microbes should be effective for biofouling mitigation in MBR.