Experimental Study On Treatment Of Macrolide Antibiotic Wastewater By Membrane Bioreactor（MBR）

Macrolide antibiotics are one of the most important antibiotics,which are widely used in humans and animals.Unlike many other pollutants present in the environment,antibiotics have direct biological effects on microorganisms.Many of these antibiotics are not completely metabolized or eliminated in the body,30%-90%of antibiotics are a mixture of urine and excrement,which is excreted by parent compounds or a mixture of various metabolites.Antibiotics and other drugs,including their precursor compounds and conversion products,are usually discharged into the environment after wastewater treatment processes（through sewage treatment plants or domestic septic tank systems）,which usually do not remove them from wastewater.When these antibiotics enter natural waters,they may cause ecological damage and potentially adverse effects on various organisms.In addition,due to the wide spread of antibiotics in water environment,the genes of antibiotic-resistant bacteria themselves can be considered as"pollutants and superbugs".Therefore,more and more attention has been paid to improving the efficiency of antibiotic removal in wastewater treatment system.In this experiment,membrane bioreactor was selected to study its treatment efficiency for macrolide antibiotic wastewater.Three macrolide antibiotics with similar physical and chemical properties were selected as treatment targets,and the macrolide antibiotics in water environment were analyzed by solid phase extraction-liquid chromatography.MBR uses inoculation training method to cultivate and domesticate th e activated sludge in the system.After the reactor is started successfully,the best operating condition of the process is determined by adjusting the operating parameters,and the removal efficiency of COD and ammonia nitrogen is investigated;Different kinds and concentrations of antibiotics were added to the influent,and the effects of antibiotics on the operation efficiency of the reactor were investigated.The efficiency and process characteristics of MBR process for treating antibiotic wastewater were explored.The following main conclusions were drawn:（1）Solid phase extraction-liquid chromatography can be used to detect the residues of macrolide antibiotics in water environment.The conditions of liquid chromatography and solid phase extraction were optimized respectively.Under the optimum conditions,the baseline separation of three macrolide antibiotics can be achieved within 10min,with moderate retention time and good peak shape;The recoveries of the three macrolide antibiotics ranged from 75.31%to 98.07%.（2）In order to shorten the start-up time of the reactor as much as possible,artificial water distribution is used as the test water of the reactor,and the method of not discharging excess sludge is adopted in the activated sludge cultivation process.Raised to 9500 mg/L,the decontamination ability of MBR is good and stable at this time,the removal rate of COD and ammonia nitrogen can reach about 85%and 86%respectively,and the effluent quality is good,which meets the requirements of"Pollutant Discharge of Urban Sewage Treatment Plant".Standard"（GB 18918-2002）in the first-class water standard.（3）By adjusting influent pH value,COD concentration and ammonia nitrogen concentration,the optimum operating conditions of MBR pro cess were explored.When pH is 7-8,the reactor shows the best working condition,and the effluent quality is better,especially the ammonia nitrogen concentration in the effluent is lower to 3.3 mg/L,which meets the first-class A effluent standard in the standard;When the influent COD concentration is 300～400 mg/L,the reactor has the best operation efficiency,the removal rate of COD is 85%,and the removal rate of NH₃-N is 85.7%;When the influent concentration is 40 mg/L,the removal rate of COD and NH₃-N is 85.6%and 85%,respectively.（4）The addition of antibiotics will affect the treatment efficiency of the reactor,and with the increase of antibiotic concentration,the removal rate of antibiotics will decrease.With the increase of antibiotic concentration in the reactor,the removal rates of COD and NH ₃-N decreased obviously,especially in the first stage,when the reactor was exposed to three antibiotics,the removal rates of COD and ammonia nitrogen decreased by 14.6%and 16.9%,respectively.Three target antibiotics can be removed by MBR reactor,roxithromycin removal efficiency is the best,followed by clarithromycin,azithromycin effect is the worst.The removal rate of roxithromycin decreased from 77.3%at 100μg/L to 58.9%at 300μg/L,clarithromycin decreased from 72.2%to 52.2%,and azithromycin decreased from 71.7%to 51%.