Mechanistic Insights into Quorum Quenching-Mediated Control of EPS and Biofilm Formation in Submerged MBR

Quorum quenching (QQ) is a promising biological approach that has the potential to control membrane biofouling. However, the implementation of the QQ membrane bioreactor still requires a more systematic and comprehensive understanding, including the selection of membrane materials, the determination of the optimal QQ bacterial dosage, and the use of appropriate media for the immobilization of QQ bacteria, all of which are important to ensure long-term operation. The present study investigated the impact of QQ bacteria on biofilm formation across different polymeric membranes. These include flat sheet membranes, Polytetrafluoroethylene (PTFE), Polysulfones (PSs), and hollow-fibre polyvinylidene difluoride (PVDF) membranes. It also evaluated biofilm development, membrane filtration performance, extracellular polymeric substance (EPS) production, and sludge floc properties, which were characterized using fluorescence microscopy. The results revealed that QQ intervention markedly suppressed quorum sensing (QS), leading to a pronounced, dose-dependent reduction in biofilm thickness, membrane fouling, EPS production and sludge floc size. Biofilm thickness was reduced by 63.5% on PTFE and 55.4% on PS membranes, accompanied by a notable reduction in EPS protein and polysaccharides, thereby weakening the biofilm formation and enhancing membrane filterability. Therefore, the permeability performance of the PVDF membrane improved by 338.2%. Furthermore, sludge settleability was enhanced, and floc size was reduced, resulting in the mitigation of biofilm formation without impacting pollutant degradation. These findings elucidate the material-dependent and dose-responsive mechanism by which QQ regulates EPS synthesis and biofilm formation in MBR.