Antibiotic Pollution Characteristics And Risk Assessment In Xuzhou Urban Sewage Treatment System

Studies have shown that common sewage treatment plants cannot completely remove antibiotics.Antibiotic residues in sewage treatment systems will inhibit the metabolism of microorganisms,thereby affecting the removal efficiency of conventional pollutants in the sewage treatment plant.In addition,the long-term presence of antibiotics breeds resistant bacteria and resistance genes,and resistant pathogens discharged from sewage treatment plants into natural water bodies will be a potential risk to human health.Therefore,it is very necessary to carry out research on the pollution characteristics of antibiotics in urban sewage treatment systems and conduct risk assessment.Ultra Performance Liquid Chromatography with tandem Mass Spectrometry(UPLC-MS/MS)was used to determine the concentration of antibiotics in three sewage treatment plants and their upstream-and downstream-receiving river in Xuzhou,China.The distribution and pollution characteristics of 19 antibiotics including eight macrolides(azithromycin,clarithromycin,josamycin,tilmicosin,rifaximin,lincomycin,erythromycin and roxithromycin),six quinolones(ofloxacin,difloxacin,enrofloxacin,cinoxacin,nalidixic acid and fleroxacin)and five sulfonamides(sulfapyridine,sulfadiazine,sulfamethoxazole,sulfamethoxypyridazine and sulfamethizole)in sewage treatment systems,as well as the concentration distribution of their upstream and downstream rivers were analyzed.Ecological risks of some antibiotics(azithromycin,lincomycin,erythromycin,roxithromycin,ofloxacin,enrofloxacin,sulfapyridine,sulfadiazine,sulfamethoxazole)in the effluents and receiving rivers of sewage treatment plants were evaluated by risk quotient method.Health risks of some antibiotic residues(clarithromycin,lincomycin,erythromycin,roxithromycin,enrofloxacin,sulfamethoxazole and sulfamethizole)in adults and children were evaluated by Monte Carlo method which based on risk quotient method.The main results are as follows:(1)The concentration of 19 antibiotics varied from <1ng/L to 1.73?g/L.The most frequently detected antibiotics were azithromycin,ofloxacin,clarithromycin and lincomycin.Azithromycin and ofloxacin have the highest concentration.(2)The concentration of most antibiotics in the sewage treatment system showed a decreasing trend,while the variation of some antibiotics in each sewage treatment unit was not obvious.Most antibiotics have the highest removal efficiency in the biological treatment stage which is the most important way of antibiotic degradation in sewage treatment plants.The removal of antibiotics in sewage treatment plants varies by antibiotic category,which are 6%-76% for macrolides,-21-64% for quinolones and-184-62% for sulfonamides.(3)The majority of upstream antibiotics levels were lower than in the downstream,indicating that sewage treatment plants are a source of antibiotics and discharge them into the receiving rivers.(4)The results of ecological risk assessment show that most antibiotics are at medium and low risk in the outfalls and receiving rivers of sewage treatment plants.Ofloxacin,lincomycin and sulfamethoxazole showed high risks and azithromycin showed a low risk.(5)The results of human health risk assessment showed that the antibiotic residues in the rivers discharged from the sewage treatment plants in Xuzhou were at a very low level for human health risks.