Treatment Of Antibiotics And Estrogens In Livestock Wastewater

In recent years,emerging contaminants including antibiotics and hormones in livestock wastewater have brought great threats to the ecological environment security and human health,which has attracted the attention of academic community and governments.In Shanghai,the conventional livestock wastewater treatment is anaerobic-based and the effluent is returned to the farmland.The typical process is "wastewater→biogas digester→storage pond→ return to farmland",which has poor ability to reduce antibiotics and hormones,and has a high risk of contamination by emerging pollutants.This study developed a cost-effective and resourcerecovery based method for the treatment of tetracycline antibiotics(TCs),sulfa antibiotics(SAs)and estrogens from swine and dairy wastewater in livestock breeding.The key lies in how to remove antibiotics and hormones effectively aerobic biodegradation and at the same time retain the ammonia nitrogen in the livestock wastewater.In this study,the nitrification inhibitor 2-chloro-6-trichloromethylpyridine(TCMP)was added to the aerobic biological treatment unit to inhibit the nitrification of ammonia nitrogen.The effect of TCMP on nitrification inhibition and the removal of TCs and estrogens were investigated.The degradation pathways of TCs in aerobic activated sludge system was preliminarily discussed.The removal of TCs by catalytic O3 oxidation from the effluent of sequencing batch reactor(SBR)was investigated.In addition,a pilot study for the treatment of dairy wastewater by anoxic-oxic(A/O)process was conducted in Zhenhua Dairy Cows Co.,Ltd.,Shanghai.The effects of TCMP on nitrification inhibition and SAs degradation were investigated.The experimental results show that:(1)SBR reactor was used to treat swine wastewater.When more than 5 mg/L TCMP was added into the system,the nitrification was almost completely inhibited.The higher TCMP concentration resulted in a shorter time to inhibit nitrification and the a greater influence on COD degradation.The COD removal efficiency was 10%lower after the complete nitrification inhibition.(2)The degradation of TCs was affected after TCMP was added to the aerobic system for the treatment of swine wastewater to inhibit ammonia nitrification.The removal efficiency of TCs was decreased gradually with the increase of the operation time of the SBR.On the 39th day,the removal efficiencies of TCs in SBR-A(control)and SBR-D(adding 10mg/L TCMP)reactors were about 86%and 75%,respectively.On the 174th day,it reached about 63%and 61%,respectively.However.the relative removal efficiency of oxytetracycline(OTC),aureomycin(CTC),tetracycline(TC)and doxycycline(DC)was not affected with the addition of TCMP.Whether nitrification was inhibited or not,the removal efficiency of the four TCs always follows the decreasing order of CTC>DC>TC≥OTC.(3)Five estrogens including estrogenone(E1),ethinylestradiol(EE2),bisphenol A(BPA),estriol(E3)and diethylstilbestrol(DIE)were effectively removed by aerobic biodegradation.After the sludge was maturely acclimated,the removal efficiency of E3,BPA,E1,EE2 and DIE was>95%.The effect of TCMP on the aerobic degradation of estrogen was negligible.(4)Iron-shaving catalyzed O3 oxidation was used to degrade TCs in SBR effluent.The removal efficiencies of OTC,CTC,DC and TC reached 83.2%,61.5%,78.3%and 81.5%,respectively,under the reaction conditions of 100 g iron,20 mg/L O3,and 6 min reaction time.The response surface method was used to design the experiment and the response surface model was established by Design-Expert 11 software to optimize the parameters.When the O3 flow rate was 300 mL/min,the optimal conditions were:O3 concentration of 50 mg/L,catalyst dosage of 68 g/L,reaction time of 10 min.The maximum removal efficiency for TCs was predicted to be 99.7%,and the actual TCs removal efficiency under the optimal process condition was 97.9%.The error between the predicted and actual value was less than 5%.The more COD residual in the biotreated effluent resulted in the worse degradation of TCs.The removal efficiency of TCs decreased from 91.5%to 72.8%after the repeated use of iron shavings for ten times.(5)The main removal pathways of OTC,CTC,DC and TC in the aerobic process were sludge adsorption and biodegradation.TCs were rapidly adsorbed by activated sludge during the initial contact period and subsequently degraded slowly.The total removal efficiencies(including the effects of adsorption,biodegradation,and hydrolysis)for OTC,CTC,DC and TC in simulated wastewater reached 98.3%,94.2%,97.1%and 96.2%,respectively,after 48 h contact with aerobic activated sludge,only 29.5%,53.1%,41.1%and 34.2%for sole biodegradation.(6)Dairy wastewater was effectively treated by an A/O pilot plant.The average removal efficiency for 10 SAs,including trimethoprim(TMP),sulfamethoxazole(SMX),sulfadiazine(SD),sulfathiazole(STH),sulfamethazine(SMR),sulfamethizole(SMZ),sulfadimidine(SMT),sulfamethoxypyridazine(SMP),sulfachloropyridazine(SCP)and sulfamethoxine(SMM),was 92%during the stable operation stage.(7)Nitrification of ammonia nitrogen was effectively inhibited after the periodical addition of TCMP with an appropriate amount into the oxic tank of A/O pilot plant.TCMP did not affect the degradation of SD,STH,SMR,SMZ,STZ,SMP,SCP,SMX and SMM.TCMP had a negative effect on TMP degradation.reflected by 24%decrease of removal efficiency.