Performance evaluation and numerical modeling of permeable reactive barrier for removal of antibiotic resistance genes from groundwater.

Antibiotics are widely used in medical and agricultural activities, which induce the spread of antibiotic resistance genes (ARGs). Once in aquifer, ARGs would gradually transport through groundwater flow, which calls for proper remediation technologies to control their dissemination. This paper carried out batch experiments to investigate the removal efficiency of ARGs by biochar, ZVI and their mixtures at the ratio of 1:1 (M11) and 1:6 (M16). Results showed that the mixed material achieved higher removal rate of ARGs from raw water, which was mainly attributed to larger adsorption rate from well-dispersed ZVI particles. sul1 was more recalcitrant than ermB and aadA, which was tightly correlated with its bacterial hosts that resisted degradation. Furthermore, column experiments were carried out, and these materials were packed at the middle section of column as the permeable reactive barrier (PRB). Results showed that M16 was the most effective material to reduce the ARGs abundance in the effluent especially for sul1 and ermB. As a representative type of mobile genetic elements, intI1 was also greatly removed by PRB. A numerical model was established to well simulate the experimental results, which demonstrated that the high remediation efficiency of M16 was mainly induced by large adsorption rate of ARGs on material interface. Besides, a higher groundwater flow rate and smaller particle size of porous media both reduced the removal rate of ARGs by PRB. The findings of this study could guide the application of PRB to remediate groundwater with high abundances of ARGs.