Mitigating vertical clogging and managing blockage migration in bioelectrochemical constructed wetlands:...

Constructed wetlands (CWs) often experience declining efficiency due to clogging during long-term operation, traditional prevention and control methods are costly and prone to causing secondary pollution. This study innovatively integrated a bioelectrochemical system (MEC) with a vertical flow CW, forming a CW-MEC system. By regulating the electrification time (4.5 h, 9.0 h, 13.5 h within an 18-h hydraulic retention time cycle), it investigates the system's impact on alleviating clogging and the migration mechanisms across distinct vertical layers. The results demonstrated that a 9.0 h electrification time (ET) significantly enhanced the overall system performance. The quartz sand layer exhibited the smallest decrease in porosity, which was 0.87 compared to 0.71 in the control, while maintaining a stable COD removal rate of 61 %. Furthermore, it effectively regulated the composition of extracellular polymeric substances (EPS). The electric field promoted directional migration of blockage, with negatively charged EPS migrating towards the anode and inorganic precipitates migrating towards the cathode. Notably, the migration potential of Soluble-EPS (S-EPS) towards the anode increased by 116 % compared to the control. This resulted in a reduced total amount of clogging substances in the quartz sand layer, achieving "intermediate layer protection". This study, for the first time, reveals the vertical spatial migration patterns of blockage under electric field regulation and proposes the novel "sacrificial protection" mechanism of the electrode layers for the quartz sand layer. This provides an innovative strategy for the long-term and low-carbon operation of CWs.