Bioremediation Of Combined Pollution Of Nitrate And Antibiotics In Groundwater

In this experiment,a highly efficient iron ion self circulating denitrifying bacteria was isolated and purified from reservoir sediments.It was identified by 16Sr DNA that strain L2 was Zoogloea.The optimal condition for determining the nitrate removal rate by response surface method is that when the temperature is 30.60℃,p H is 6.75 and Fe²⁺concentration is 27.86mg/L,the nitrate removal rate is 75.44%.Anthraquinone-2-sulfonic acid（AQS）,fulvic acid（FA）,2-hydroxy-1,4-naphthoquinone（HNQ）and Fe₃O₄were selected to study the effects of different redox mediators on denitrification.The results showed that HNQ had the best effect on the enhancement of bacterial denitrification.The effect of hnq concentration on denitrification was investigated.It was found that the highest removal rate of nitrate was 90.85%in 12h,which was higher than that without HNQ,which was 74.80%.The redox potential and bacterial density were greatly affected by HNQ concentration.Three dimensional fluorescence analysis was used to analyze the change of organic matter under different HNQ concentrations.It was found that the intensity of fluorescence peak decreased with the increase of HNQ concentration,indicating that the organic matter increased with the increase of HNQ concentration,and the microbial utilization increased.Gas chromatography was used to analyze the change of gas composition produced by strain L2 under different HNQ concentrations.It was found that nitrogen was the final product in denitrification process,and the proportion of nitrogen composition was related to denitrification efficiency.The metabolites of the strain were collected from the iron rich medium and prepared into biosorptive agent.The main components of Fe OOH and Fe₃O₄were analyzed by XRD.The adsorption of tetracycline by biosorption agent was studied.The effects of p H,temperature,amount of biological precipitation and ionic strength on TC adsorption were investigated.The results showed that when the temperature was30.00℃and p H was 6.0,the adsorption rate of tetracycline was the highest when the adsorption dose was 50 mg/L,which was over 90%,while the addition of Cu²⁺greatly weakened the adsorption capacity of tetracycline,and the adsorption rate decreased to below 10%.When KCl was selected to study the effect of ionic strength on adsorption,it was found that the adsorption capacity and removal efficiency decreased with the increase of KCl concentration.In the experiment of adsorption kinetics,it is found that the data fitting is more in line with the elovich model,and the adsorption process is mainly related to chemical adsorption.In the isothermal adsorption experiment,Langmuir model fitted well.The adsorption of TC was the result of interaction of various mechanisms,mainly controlled by chemical interaction.In the study of adsorption thermodynamics,according to the analysis of thermodynamic parameters,it shows that the adsorption process is endothermic process,mainly chemical adsorption.The application of biosorption agent in advanced oxidation process can fully catalyze peroxide and effectively degrade tetracycline due to the high composition of iron oxide.PVA chitosan was used as the bio filler of the reactor,and the strain was fixed in the material.Under different C/N,Fe²⁺concentration and HRT conditions,the removal effect of nitrate,phosphate and tetracycline by adding different materials to the reactor was studied.The results showed that when C/N was 2,HRT was 6 hours,Fe²⁺concentration was 30 mg/L,the best performance of the reactor was obtained（nitrate removal rate was 100%,phosphate removal rate was 80.48%,tetracycline removal rate was stable at about 80%）.High throughput sequencing was used to analyze the microbial community composition and structure of different experimental groups in the bioreactor.The results showed that strain L2 played a leading role in the whole denitrification process.Sodium alginate was used as the carrier of immobilization reactor,and iron powder and iron carbon were added respectively.Strain L2 was fixed in the material.Under different C/N,p H and HRT conditions,the removal effect of nitrate,nitrite and ammonia nitrogen in the reactor was studied.The results showed that when C/N was 3,p H was 7 and HRT was 6,the reactor had the best reaction effect（nitrate removal rate was 100%,no nitrite nitrogen and ammonia nitrogen accumulation）.The composition and structure of microbial community in different experimental groups of the bioreactor were analyzed by high-throughput sequencing.The results showed that Zoogloea was the main genus of the reactor.The morphology and crystal structure of the precipitates were characterized by SEM and XRD.