Polyelectrolyte-silica composite quorum quenching biomedia as new antifouling agents for anaerobic membrane bioreactor treatment

Anaerobic membrane bioreactors (AnMBRs) have received increasing attention because of their low energy requirements; however, membrane fouling is the major deterrent to their widespread application. Here, we report a novel composite biomedium composed of quorum quenching (QQ) bacteria (Rhodococcus sp. BH4), porous silica, and polyelectrolytes for biofouling control in AnMBRs. The facultative character of BH4 is described for the first time, showing its QQ activity (the pseudo-first-order rate constant of degradation of N-octanoyl-l-homoserine lactone, 15.3–16.3 h⁻¹) and biofilm inhibition (33–44 % reduction compared to the control) under anaerobic conditions. The results showed that the composite QQ media caused a significant delay in AnMBR membrane fouling (>2.5 and 1.9 times, respectively) compared to the cases with no or vacant media. The QQ media maintained >90 % of its original tensile strength after 40 days of use in the AnMBR, exhibiting more excellent durability than hydrogel-based media. QQ media contributed to the reduced production of biopolymers (e.g., proteins) and signal molecules (e.g., short- and medium-chain acyl-homoserine lactones) in the AnMBR. Finally, the QQ media did not impact anaerobic treatment performance, such as organic removal or methane production. The findings of this study demonstrate the QQ efficacy and sustainability of the BH4 strain and its composite media in AnMBRs.