Dual-bioaugmentation strategy to simultaneously mitigate biofouling and promote methanogenesis in AnMBR

Anaerobic membrane bioreactor (AnMBR) is a promising technology for resource and energy recovery from wastewater owing to its high-quality effluent and methane production. However, membrane fouling and susceptible methanogenesis have ever compromised the AnMBR. This work attempted to mitigate membrane fouling and promote methane production simultaneously in AnMBR through bioaugmentation with a consortium consisting of both quorum quenching (QQ) bacteria and methanogens. To obtain the dual-functional consortium, N-acyl homoserine lactone (AHL) and gamma-caprolactone (GCL), which could serve as QQ biostimulants as well as carbon sources for fermentation and methanogenesis, were used as sole carbon sources in the anaerobic enrichment, and the obtained consortia were denoted as An-A and An-G respectively. Facultative cultivations with AHL or GCL, denoted as F-A and F-G, were also obtained for comparison. The results indicated that the An-G consortium showed superior AHL degrading activity, and EPS suppressive and methanogenic capacity. The moderate anaerobic QQ activity and low methanogenic capacity of F-G consortium may be attributed to the oxygen exposure in the cultivation. The AHL consortia in either anaerobic or facultative condition, i.e. the AN-A and F-A, showed good QQ activity but compromised methanogenic activity, due to the inhibition of acetoclastic methanogens by free ammonia introduced by the acylamino group in AHL. The optimal consortium, An-G, was immobilized and added to AnMBR. The membrane fouling in An-G AnMBR was significantly retarded to 2 times, and the cumulative methane production was elevated by 18.0 % compared to the control reactor. This work demonstrated that the dual-bioaugmentation with anaerobic GCL enrichment consortium successfully mitigated fouling and promoted methanogenesis simultaneously in AnMBR, which is considered to be highly promising in enhancing AnMBR and facilitating resource and energy recovery from wastewater.