Aquifer clogging caused by chlorine disinfection during the reclaimed water recharge

Aquifer clogging plays a critical role in the efficiency of reclaimed water recharge. While chlorine disinfection is commonly used for reclaimed water, its impact on clogging has seldom been discussed. Thus, this study aimed to investigate the mechanism of chlorine disinfection on clogging by establishing a lab-scale reclaimed water recharge system that utilized chlorine-treated secondary effluent as feed water. The findings indicated that increasing the chlorine concentration led to a surge in the total amount of suspended particles, and the median particle size increased from 2.65 μm to 10.58 μm. Furthermore, the fluorescence intensity of dissolved organic matter decreased by 20%, with 80% of these compounds, including humic acid, becoming entrapped within the porous media. Additionally, the formation of biofilms was also found to be promoted. Microbial community structure analysis unveiled a consistent dominance of Proteobacteria consistently exceeded 50% in relative abundance. Moreover, the relative abundance of Firmicutes increased from 0.19% to 26.28%, thereby verifying their strong tolerance to chlorine disinfection. These results showed that higher chlorine concentrations could stimulate microorganisms to secrete an increased quantity of extracellular polymeric substance (EPS) and form a coexistence system with the trapped particles and natural organic matter (NOM) within the porous media. Consequently, this supported the formation of biofilms, thereby potentially elevating the risk of aquifer clogging.