Study On Immobilization Of Antibiotic-resistant Bacteria And Its Degradation Of COD In Antibiotic Wastewater

Antibiotics in wastewater have a strong inhibitory effect on the activity of microorganisms,making it difficult to degrade COD in antibiotic wastewater by conventional microbial methods.The study used a strain of high concentration antibiotic-resistant bacteria（Stenotrophomonas sp.）previously discovered by the research group to prepare immobilized bacteria for the biodegradation of COD in antibiotic wastewater.Sugarcane bagasse was used as the raw material to prepare magnetic biochar by impregnation method in this paper.The preparation conditions of magnetic biochar are optimized by single factor experiment,and the biochar is characterized and analyzed.The preparation conditions of immobilized bacteria and the conditions for the degradation of COD in the original wastewater with the immobilized bacteria were both optimized by single-factor test and response surface method.The degradation of COD in wastewater by immobilized bacteria and native microorganisms in the presence of different types and concentrations of antibiotics was investigated.The following main conclusions were drawn from the above studies.（1）In this study,magnetic biochar was successfully prepared.The conditions for the preparation of magnetic biochar were optimized by single-factor tests to a pyrolysis temperature of 600°C and a pyrolysis time of 1 h.Under these pyrolysis conditions,the ability of magnetically modified biochar to adsorb microorganisms is lower than that of unmodified biochar,and the specific surface area,pore volume and oxygen-containing functional groups of the modified biochar decreased,while the average pore size increased.A large number of iron-oxygen crystal particles were scattered on the surface of the magnetically modified biochar.XRD analysis showed that the magnetic particles generated were Fe₂O₃.（2）The immobilization temperature,time and carrier dosage have a great influence on the adsorption of immobilized microorganisms on the biochar.The optimal preparation conditions of immobilized bacteria after optimization by single factor and response surface experiments are:temperature 33.1℃,time 21.1h,biochar dosage 1.28 g/L,p H=7.0,and inoculum amount 5%.（3）Immobilized bacteria can effectively degrade COD in original wastewater.For the original wastewater without antibiotics（the native microorganisms in wastewater have been removed）,the immobilized bacteria can effectively remove COD from the wastewater within 30 h（with a degradation rate of more than 50%）.The optimal conditions for the degradation of COD of wastewater by immobilized bacterial agents after optimization by single factor and response surface experiments are:shaker speed 171 r/min,bacterial agent dosage 5.12 g/L,p H=5.9,temperature 30℃,here Under the conditions,the predicted degradation rate of COD is 67.3%.（4）Immobilized bacteria can effectively increase the degradation rate of COD in antibiotic wastewater.Combination antibiotics can inhibit the degradation of COD by native microorganisms in original water more strongly than single antibiotics.Therefore,after adding immobilized bacteria,the degradation rate of COD in the wastewater of combined antibiotics has a greater increase.Adding immobilized bacteria to five single antibiotic（ofloxacin,hygromycin,cephalothin,penicillin and sulfamethazine）wastewaters with concentrations ranging from 10 to 100 mg/L,the COD degradation rates of the wastewater were increased by 7.8–23.1%.And the degradation rates of wastewater COD were significantly increased by 10.3-40.9%,when immobilized bacteria were added to five combinations of antibiotic wastewater with total concentrations of 10-100 mg/L of penicillin+ofloxacin,penicillin+hygromycin,penicillin+cephalothin,ofloxacin+hygromycin and hygromycin+cephalothin,respectively.