Transport Characteristics And Removal Of Typical Sulfonamide Antibiotics During Recharge Of Surface Water

Recharging of surface water to groundwater will introduce trace toxic and hazardous substances that pose potential risks to groundwater and trigger groundwater environmental safety issues.In this study,two typical sulfa antibiotics(sulfamethoxazole(SMX)and trimethoprim(TMP))based on field investigation results were selected,and corn stover,wheat straw,and bagasse-derived biochars prepared by oxygen-limited temperature-controlled carbonization method were used.Biochar was used as a filler medium modification material to construct a biochar enhanced soil aquifer treatment(SAT)system to remove SMX and TMP.The main results are as follows:Compounds with the highest detection rate and detected concentration in source water/groundwater in the surface water recharge area investigated were SMX and TMP.The concentrations of SMX and TMP in the source water were 1.83 to 5.55 ng/L and 4.23 to 10.59 ng/L,respectively.The detected concentrations of SMX and TMP were as high as 17.5 ng/L and 79.4 ng/L,23.1 ng/L and 71.4 ng/L in shallow groundwater and deep groundwater,respectively.Among them,the ecological risk assessment result of SMX is a potential medium risk,and TMP has a potential low risk.The results of column experiments with multiple water source recharge simulations showed that the investigation of the aeration zone has a weaker effect on the adsorption and physical retention of SMX and TMP.SMX and TMP can easily migrate into groundwater,and long-term recharge causes higher groundwater pollution risks.With the increase of carbonization temperature(from 300°C to 700°C),the specific surface area and total pore volume of biochar increased and the adsorption sites increased,which enhanced the adsorption capacity of biochar on SMX and TMP.In the single solute system,each biochar has stronger TMP adsorption capacity than SMX.Under experimental pH conditions(pH=6~7),SMX and TMP exist mainly in anionic and cationic forms,respectively,and the surface of biochar is negatively charged.The adsorption of biochar on SMX and TMP is influenced by different electrostatic effects.When the mass ratio of biochar prepared by adding high temperature(500°C and 700°C)to the filling medium was 2.08%,the removal efficiency of SMX and TMP from biochar-modified SAT was better than that from non-biochar modified SAT with TMP removal rate up to 96%.The SAT constructed with biochar at 500°C had good retention capacity for SMX.The adsorption capacity of biochar per unit mass for SMX was about 1000 ?g/g,indicating that biochar enhanced SAT has great potential in removal of SMX and TMP in the environment.