Coupled effects of bacteria and suspended solids on clogging during managed aquifer recharge

Managed aquifer recharge (MAR) is an effective strategy for relieving water shortages and their related environmental problems. However, clogging is a major issue in MAR implementation. Bioclogging occurs when nutrients and suspended solids (SS) are available in the water to which bacteria can be attached and subsequently form larger aggregations that result in porous media clogging. The combined clogging of SS and Pseudomonas aeruginosa (P.a) bacteria was investigated using a series column experiment, and scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), correlation analysis, and pathway analysis were employed to identify the combined clogging interaction between SS and P.a. Low SS concentrations exhibited high mobility and improved the migration of P.a as carriers, while high SS concentrations promoted the deposition of P.a. Thus, SS changed the stage characteristics of bioclogging, and the order of the clogging rate was as follows: SS-P.a group > P.a group > SS group. The interaction mechanisms of the combined clogging included bridging ions, chemical bonds, functional groups, extracellular polymeric substance polymerization, and improved adhesion within the SS-P.a sand system, which formed polymers with large particle sizes that occupied the pores and narrowed the flow path, causing the media to clog. The correlation and pathway analyses demonstrated that the direct effect of biomass was larger than SS on combined clogging, but the indirect effects of biomass were less than those of the SS, indicating that a series of interactions occurred during the SS-P.a combined clogging, and more special attention should be paid to the interaction of SS and bacteria during the aquifer recharge process.