Research On Treatment Technology Of Antibiotics In Swine Wastewater

The excessive consumption of antibiotics in the livestock industry has become one of the main causes of antibiotic contamination in the natural environment.Sulfonamides(SAs)and β-lactams are two main groups of antibiotics used in the pig industry.We evaluated the removal performance of SAs and β-lactams in swine wastewater by anaerobic and aerobic biological treatment processes.The effects of hydraulic load and sludge concentration on the antibiotic removal efficiencies have been investigated.Sulfamonomethoxine(SMM)and sulfamethoxazole(SMX)as the dominant antibiotics in swine wastewater have been used as model antibiotics for the performance evaluation of powdered activated carbon(PAC)adsorption and advanced oxidation technology(i.e.,UV/H2O2).The effect of operational conditions of PAC adsorption and UV/H2O2 has been assessed.The intermediate products and degradation pathways of SMM by UV/H2O2 have been discussed as well.The following conclusions can be drawn from this study:(1)The on-site wastewater treatment process with an anaerobic digestion tank(AD,i.e.,biogas pool)and a storage pond was used to treat the swine wastewater in a pig industry in Jinshan District in Shanghai.Nineteen antibiotics including SAs and β-lactams were detected in swine wastewater in the summer and autumn of 201 8 with a total concentration of 99.2～339.3μg/L,of which more than 95%was SMM.The residual antibiotics in the storage pond effluent were～19.1～21.1μg/L.(2)AD process effectively removed the conventional organic pollutants(i.e.,COD removal efficiency of 77%),while the removal efficiency of antibiotics,SMM in particular,was relatively low(<25%).The increase of sludge concentration favored the removal of conventional pollutants,while had little effect on the antibiotic removal.The degradation effects of the main SAs in swine wastewater by AD followed a decreasing order of sulfamethoxazole(SMX)>sulfadiazine(SD)>sulfamethazine(SMZ)>sulfamonomethoxine(SMM).(3)The total removal of SAs and β-lactams was 93%when the sequencing batch reactor(SBR)under a hydraulic retention time(HRT)of 10 d was used to treat the AD effluent.The removal efficiencies of both SAs and β-lactams reduced with the HRT reduced from 10 to 3.3 d.The decline of the removal rate of β-lactams was more significant than that of SAs.However,the total removal rate of the antibiotics were still above 80%.(4)The total antibiotic removal was above 80%when the SBR was directly used to treat the swine wastewater under an HRT of ≥ 3.3 d,which indicated the significant role of aerobic unit for antibiotic removal in the biological treatment process.The degradation efficiency of SAs in swine wastewater by SBR followed a decreasing order of SD>SMX>SMZ>SMM.(5)The antibiotics in the simulated wastewater were removed rapidly after the addition of PAC,reaching an adsorption equilibrium in 120 min.The neutral and acidic environment was conducive to the adsorption of SMM and SMX by PAC.The effect of pH on SMX adsorption was greater than that of SMM.The removal rates of SMM and SMZ were 91%and 82%respectively by using 20 mg/L PAC to treat the simulated wastewater with 500 μg/L SMM and SMX(corresponding to the equilibrium adsorption capacities of 22.7 and 20.5 mg/g).The PAC advanced treatment to the combined anaerobic and aerobic biodegradation effluent(the addition of 100 mg/L PAC)further reduced the antibiotic concentration from 25.6 to 17.6μg/L(with a removal rate of 31.2%)(6)The UV/H2O2 was used to treat simulated antibiotic wastewater with SMM and SMX concentrations of 1000 μg/L.The removal rates of SMM and SMX were 98.8%and 97.2%respectively under the reaction conditions of pH 7.0,0.1 mmol/L H2O2 dosage,and reaction time of 8 min.The reaction followed a pseudo first-order kinetic model.The degradation rate constant of SMX was larger than that of SMM under the same reaction conditions.The reaction rate increased with the increase of H2O2 dosage.The neutral and weakly alkaline conditions promoted SMM degradation,while weakly acidic conditions favored SMX degradation.The NO3-promoted the degradation of SMM and SMX,while the presence of HCO3-/CO32-played a negative role.The hydroxylation of benzene and pyrimidine rings in SMM molecule during UV/H2O2 oxidation process was prior to the cleavage of S-N bond.(7)The UV/H2O2 treatment for the combined anaerobic and aerobic biodegradation effluent with the extra addition of 1000μg/L for SMM and SMX demonstrated good degradation performance.The H2O2 dosage was much higher than that for simulated wastewater treatment.The conventional contaminants and turbidity in wastewater were the main inhibition factors of SMM and SMX degradation by UV/H2O2.(8)The UV/H2O2 advanced treatment for the combined anaerobic and aerobic biodegradation effluent reduced the antibiotic concentration from 67.1 to 15.8μg/L under the reaction conditions of 10 mmol/L H2O2 and 60 min UV radiation.The antibiotic removal rate was 76.4%.