Application and mechanism of quorum sensing in biological wastewater treatment systems: Current state and future prospects

Quorum sensing (QS) plays a pivotal role in bacterial interactions and is crucial for enhancing the efficiency and stability of biological wastewater treatment (BWT) systems. However, the diversity of BWT processes and the complexity of QS pose challenges to understanding their functionality. This review uses bibliometric tools to synthesize research from the past two decades, capturing the significant growth in research in this field driven by China, Korean, and U.S. researchers. The research hotspot has shifted from initial basic research on 'gene expression' and 'biofilm formation' to applied studies on 'start-up', 'denitrification', 'nitrification', and 'temperature', along with interdisciplinary explorations. Keyword cluster analyses reveal key themes, including quorum quenching, biofilm formation, membrane fouling, and antibiotic resistance genes. Subsequently, this review explores current applications and mechanisms. Enhanced QS promotes pollutant removal through modulation of microbial metabolism and energy; enhances microbial robustness through modulation of extra- cellular polymeric substances (EPS), resistance to oxidative stress, and activation of specific genes and transporter proteins; and facilitates biofilm and granular sludge formation through modulation of adhesion and EPS. Additionally, weakening of QS mechanisms reduces membrane fouling and mitigates sludge bulking by inhibiting community behavior and modulating EPS. It also summarizes reported QS regulatory strategies, including chemical activators/inhibitors, sustainable bioregulation using specific microbes, and engineering approaches for optimizing environmental conditions and design parameters. Future research should focus on deepening understanding, exploring optimization potential, and investigating sustainability and ecological safety to maximize the potential of QS in BWT systems and gain key insights into the application of QS technologies.