Mitigating Bio-Clogging in Subsurface Flow Constructed Wetlands via Quorum Quenching: Performance Evaluation and Mechanistic Insights
Subsurface flow constructed wetlands (SSFCWs) have been widely applied for sewage wastewater remediation due to the efficient utilization of wetland space and considerable improvement in treatment capacity. However, bio-clogging driven by the accumulation of extracellular polymeric substances (EPS) severely restricts their longevity and hydraulic performance. To address this issue, two quorum quenching (QQ) strategies based on Rhodococcus sp. BH4 and porcine kidney acylase I were developed to alleviate bio-clogging in SSFCWs. Compared with the control, the two QQ treatments increased hydraulic conductivity by 1.1 to 1.3 cm/s and further improved chemical oxygen demand and ammonia-nitrogen removal efficiencies by up to 12.1% and 10.3%, respectively. Concentration of the representative acyl-homoserine lactone (AHL) signal molecule C8-HSL markedly decreased from 45.8 ng/L to 15.0 ng/L, suggesting that both QQ treatments attenuated QS through AHL hydrolysis. This decrease was accompanied by a 13.1% to 30.8% reduction in the total EPS content. Notably, the QQ strategies suppressed the proliferation of clogging-associated anaerobic microorganisms such as Clostridium. Meanwhile, key genes associated with QS and EPS synthesis, including luxR and algD, showed lower predicted relative abundances. This pattern may have contributed to the formation of a looser, more hydrophilic, and clogging-resistant biofilm structure, thereby facilitating oxygen and substrate transfer within the biofilm and ultimately improving pollutant removal. Overall, this study revealed that the QQ-based approach could shift bio-clogging control from passive mitigation to proactive, source-oriented ecological regulation, providing new insights into maintaining the hydraulic function and long-term operational stability of SSFCWs.