Study Of Action Rules Of Microorganism In The Treatment Of Sulfamethazine Effluent By Biological Contact Oxidation

Sulfamethazine（SMZ）is one of the typical sulfadiamine antibiotic,which is distributed widely in water environment,the long-term accumulation refractory of sulfamethazine poses a serious threat to the environment.Therefore,the sulfamethazine wastewater treatment has become highly necessitated,while the biologic contact oxidation technology has not been used for the sulfamethazine wastewater treatment.Microorganism is the main driver of biodegradation of sulfamethazine.It is of great significance to study the action rules of microorganism during the sulfamethazine wastewater treatment.This study investigated the performance of two-stage biological contact oxidation reactor on the treatment of sulfamethazine wastewater,evaluatingthe effects of sulfamethazine on extracellular polymers in this system,shift of microbial community structure and abundance of antibiotic resistance genes,further revealing the antibiotic resistance mechanism.Furthermore,the sulfamethazine degrading bacteria were isolated and screened from the system,revealing its optimal degradation conditions,these results provided the microbial strain resources for the biological treatment of sulfamethazine wastewater.The results are as follows:1.The self-designed two-stage biological contact oxidation reactor was used for the treatment sulfamethazine wastewater,and the concentration of sulfamethazine in theinfluent wasgradually increased from 0.10 mg/L（1-20 d）to 1 mg/L（21-40 d）and 3 mg/L（41-80 d）.The average removal efficiency of COD was 80.45%,the average removal efficiency of NH₄⁺-N was 73.92%,and the average removal efficiency of PO₄^3-was 40%.The removal efficiency of sulfamethazine exceeded 90%when the sulfamethazine concentration in influent was less than 1 mg/L,but it decreased to 39.36%when the concentration of sulfamethazine increased to 3 mg/L.2.The effect of sulfamethazine concentration on the extracellular polymers in the inoculated sludge（CK）,the activated sludge in day 40（Z1）and day 80（Z3）during the two-stage biological contact oxidation reactor for the treatment of sulfamethazine wastewater was further analysed.The increasing sulfamethazine concentration in the influent resulted in a significant increase in the amount of extracellular polymer.The content of tightly bound extracellular polymers increased from 10.34 mg/（g VSS）in CK to 44.33 mg/（g VSS）in Z1and 53.79 mg/（g VSS）in Z3,especially for the concentration of proteins.The content of adherent extracellular polymer decreased with the increasing sulfamethazine concentration,and its protein and polysaccharide concentrations exhibited a decreasing trend.The results of three-dimensional excitation and emission matrix fluorescence（3D-EEM）indicated that the soluble microbial metabolites and humic acid-like substances in the extracellular polymer decreased with the increasing concentration of sulfamethazine.3.The action rules of microorganism during the two-stage biological contact oxidation reactor for the treatment of sulfamethazine wastewater was investigated by the macrogenome sequencing technology.The microbial community structure shiftedsignificantly ss the sulfamethazine concentration in the influent increased,with Proteobacteria and Chloroflexi enriched and became the dominant phylum at the phylum level.At the genus level,Candidatus＿Promineofilum was enriched mostly,and had the highest correlation with sulfamethazine,which played an important role in the degradation of sulfamethazine.4.Sulfonamides was the greatest increasing antibiotic type during the two-stage biological contact oxidation reactor for the treatment of sulfamethazine wastewater,with the highest frequency of sulfonamide resistance genes were sul1 and sul2.The main potential hosts for sul1 and sul2 were Candidatus＿Promineofilum,Aromatoleum,unclassified＿d＿＿Bacteria,unclassified＿c＿＿Anaerolineae,unclassified＿c＿＿Caldilineae,unclassified＿o＿＿Bacteroidales unclassified＿f＿＿Anaerolineaceae and unclassified＿c＿＿Betaproteobacteria,especially for Candidatus＿Promineofilum,which contributed the most to the major target gene replacement resistance mechanisms for sulphonamide antibiotics.5.Seven sulfadimethylpyrimidine degrading bacteria were isolated from the activated sludge on day 80 in the two-stage biological contact oxidation reactor by pure culture technique,which were mainly classified as Firmicutes and Proteobacteria by 16S r RNA gene sequence analysis.One of the more effective sulfamethazine degraders is Exiguobacterium sp.H-1.The optimum environmental conditions for the degradation of sulfadimethoxine by strain H-1 were further optimised using response surface methodology:the inoculum level was 4%,the p H was 7 and the temperature was 28℃.The removal efficiency of sulfadimethoxine by strain H-1 was 10.54%.