Removal Of Tetracycline Antibiotics And Estrogens From Swine Wastewater

In recent years,the environmental risks caused by emerging contaminants such as antibiotics and hormones in livestock wastewater have attracted much attention from domestic and foreign scholars.Antibiotics and hormones have been widely used in livestock breeding because of their advantages such as cheap price,good antibacterial effect and promotion to animal growth.However,most antibiotics and hormones are not effectively used and discharged by animals.If these emerging pollutants are not effectively controlled,they will cause serious damage to the ecological environment.This study developed a cost-effective and resource-recovery based method for the treatment of tetracycline antibiotics(TCs),sulfa antibiotics(SAs)and estrogens from swine and wastewater in Tinglin pig farm of Shanghai Qinnong Animal Husbandry Technology Development Company.The effect of aerobic activated sludge process with short sludge retention time on the inhibition of ammonia-nitrogen nitrification and degradation of emerging pollutants was investigated.The effects of SRT and hydraulic residence time(HRT)on the removal of emerging contaminants were investigated.In addition,oxalic acid assisted F’enton oxidation for the degradation of TCs in the aerobic effluent with short SRT and the adsorption of TCs by inactivated sludge were discussed.The results show that:(1)Two TCs,oxytetracycline(OTC)and aureomycin(CTC),and three estrogens,bisphenol A(BPA),estrogenone(E1)and estriol(E3),were detected in the wastewater from Tianlin pig farm of Shanghai Qinnong Animal Science and Technology Co.,Ltd.Their total concentrations were about 19.84-27.15 μg/L and 10.52-14.09 μg/L,respectively.(2)Two TCs(OTC,CTC)and three estrogens(BPA,E1,E3)in swine wastewater were effectively treated by conventional aerobic activated sludge process.CTC was undetectable in the effluent and the removal efficiency for OTC reached 98.9%.The removal efficiencies for BPA,E1 and E3 were over 91%.(3)The sequencing batch reactor(SBR)was used to treat swine wastewater after the addition of four TCs(OTC,CTC,DC,TCN)and five estrogens(BPA,E1,E3,EE2,DIE)(100 μg/L each).Under the same HRT,SRT had little effect on the removal of estrogens,but had a great effect on the removal of TCs.Under an HRT of ≥5 d,the removal efficiencies of TCs and estrogens were increased from 73.8%to 94.5%and from 89.5%to 97.3%,respectively,after SRT was extended from 5 d to 15 d.(4)Nitrification of ammonia nitrogen was effectively inhibited by aerobic treatment with short SRT.Nitrification was almost completely inhibited when SRT and HRT were 3 d for SBR process.The removal efficiencies of TCs and estrogens were about 74.7%and 86.7%,respectively,15%and 4%decrease compared with those under a SRT of 10 d.(5)The increase of HRT resulted in better removal of emerging contaminants when SBR with short SRT was used to treat swine wastewater.Under a SRT of 3 d,the removal efficiencies of TCs and estrogens were increased by about 6.9%and 2.7%,respectively,after HRT was extended from 3 d to 6 d.(6)The advanced treatment of SBR effluent by oxalic acid-assisted Fenton oxidation broadened the initial pH range of the reaction.Under the optimal conditions of initial pH=6.0,[Fe2+]=1.25 mM,[Fe2+]:[OA]:[H2O2]=1:2:3(molar ratio),the removal efficiency of TCs was as high as 86.8%.(7)The response surface methodology was used to design oxalic-acid-assisted Fenton oxidation experiment,and Design-Expert 8.0.5 software was used to optimize the experimental conditions.The optimal conditions for oxalic-acid-assisted Fenton oxidation to degrade TCs in SBR effluent with short SRT were as follows:[Fe2+]=1.17 mM,[OA]:[Fe2+]=1.97,H2O2=3.66 mM,pH=6.0.Under these optimal conditions,the average removal efficiency for TCs was about 88.0%,which was similar to the value predicted by RSM model.(8)The adsorption of OTC,CTC,DC and TCN by inactivated sludge was very fast.Nearly 85%of the TCs was transferred from the aqueous to sludge phase after contact time of 1 hour,and the adsorption equilibrium was reached after 4 hours.The adsorption capacities followed a decreasing trend as OTC>DC>TCN>CTC.Adsorption may be one of the main pathways for the removal of TCs in SBR system.(9)The adsorption process of OTC,CTC,DC and TCN by inactivated sludge followed the Freundlich isotherm model,and the adsorption kinetics followed the pseudo-second-order kinetic model.