The Fate and Clogging Mechanisms of Suspended Particles in Natural Biofilm-Coated Porous Media

Managed aquifer recharge (MAR) is widely used globally. However, clogging events remain a major obstacle to long-term operations. This study investigated the effects of natural biofilms on the migration and deposition of suspended particles (SPs) at varying concentrations using column experiments and multiple analytical methods. At 74 h, the K′ in the high-concentration group (HT) with biofilm coating decreased by 77.3%, while, in the high-concentration group (HTCK) without biofilm coating, the K′ decreased by 68.5%. Within the same recharge time, the K′ in the medium-concentration group without biofilm coating decreased by 59.9%. The results show that the biofilm covering the porous medium promotes the clogging of suspended particles. Compared with the high-concentration group, the development of porous medium blockage was slower in the low-concentration suspended particle group. SEM and CT analyses revealed that the biofilms altered the surface roughness of the porous media, thereby promoting SP deposition. The study also confirmed that the interactions between SPs and biofilms in recharge water, including electrostatic interactions, hydrophobic interactions, and extracellular polymer flocculation, collectively exacerbated the clogging process in MAR. XDLVO analysis indicated that the biofilm-coated porous media reduced the electrostatic interaction potential energy and energy barrier between SPs and quartz sand, thereby facilitating kaolin deposition in saturated porous media. Correlation and significance analyses identified hydrophobic interactions as the primary mechanism driving SP–biofilm combined with clogging. Moreover, the reduced SP concentrations in the recharge water increased the SP migration distance in porous media, slowing the clogging progression in low-SP groups. These findings offer valuable insights into the prevention and management of MAR clogging caused by the coexistence of biofilms and SPs.