The Study On Transport And Transportation Of Typical Sulfanomides In Unsaturated Zone And The Removal Of Typical Sulfanomides By Artificial Composite Soil Treatment System

Recently,sulfamethoxazole?SMX?and trimethoprim?TMP?have been detected in sewage treatment plant water,surface water,groundwater and drinking water.SMX and TMP in the environment are maily discharged from the sewage treatment plants.Adsorption kinetics,isothermal adsorption,desorption and competition sorption were used as the methods to study on the SMX and TMP sorption properties on clay ceramsites to resolve the problem of adsorption material selection for artificial composite soil treatment system.It showed that the TMP sorption capacity?151.82 ?g/g?was bigger than SMX?51.85 ?g/g?.There is desorption hysteresis during the desorption experiment.TMP with high adsorption capacity shows strong competitive ability.The sorption experiment determined clay ceramsites as the material of adsorption layer in artificial composite soil treatment system.By using dry-wet alternate ways of recharge,we studied on the migration of SMX and TMP in vadose zone and hydrogeological processes.The results showed that SMX and TMP migration was fast and long-term recharge would inevitably result in a great risk of contamination.Dry-wet alternate ways of recharge could improve the reaeration capacity of columns.Physical entrapment and biodegradation accelerated chemical oxygen demand?COD?removal in vadose zone.Ammonia nitrogen was changed to nitrate nitrogen in the later stage of recharge process and more nitrate vertical movement might result in elevated concentration of nitrate nitrogen in groundwater.Cation exchange occurred between Ca²⁺-Mg²⁺ and Ca²⁺-K⁺.Based on the sorption experiment and the study of SMX and TMP migration in unsaturated zone,we built up artificial composite soil treatment system to remove SMX and TMP,combining the mechanism of sorption and biodegradation.During the recharge process of artificial water containing SMX and TMP,the biodegradation is not obvious and the main removal mechanism is attributed to sorption.The TMP and SMX removal rates are 80%⁹0% and 60%⁷0%,respectively and the SMX and TMP removal is related to hydrogeological processes.Importantly,the packing material does not cause secondary pollution.In the later stage of reclaimed water recharge,biodegradation is the main removal mechanism.Moreover,there was a good response between the removal of TMP and ammonia nitrogen.The fact that the effluent concentration of ammonia nitrogen and nitrate nitrogen concentrations are higher than the influent concentrations further proves that TMP biodegradation is related to nitrification.Moreover,results also show that SMX could be biodegraded in aerobic conditions.About the problems of SMX and TMP biodegradation bacteria and the biodegradation properties,bacteria from biodegradation layers of artificial composite soil treatment system were enriched,isolated and purified to obtain an effective SMX and TMP degrading strain,identified as Bacillus substils.The biodegradation behaviors of the bacteria show that the optimization conditions contain 5.0 mg/L initial concentration,30 ? degradation temperature and pH = 7.0.Nitrosomonadaceae_uncultured,Bacillus and Nitrospira are considered as the mian denitrifying bacteria genera while Bacillus and Lactococcus are the main SMX and TMP functional bacteria genera.In this study,Bacillus substils are considered as effective SMX and TMP degrading bacteria and are also nitrifying bacteria,combing the column and microbial experiment results.