Anaerobic Digestion Of Chicken Manure Contaminated By Chlortetracycline

With the development of intensive farming,the pollution of chicken manure is becoming more and more serious.Anaerobic digestion is an effective way to reduce and eliminate the pollution of chicken manure and realize its resource utilization simultaneously.However,antibiotics are widely added in large-scale chicken farming and enter the environment through chicken manure,which not only threatens the ecological balance and public health seriously,but also restricts the engineering application of anaerobic digestion of chicken manure.At present,there is no basic data on the effect of antibiotic contamination on the long-term operation of anaerobic digestion of chicken manure.In this study,the effects of chlortetracycline?CTC?on anaerobic digestion of chicken manure under batch and continuous experimental conditions were studied comparatively.The characteristics of gas production and physicochemical properties of digester under the two conditions were analyzed.The performance of anaerobic digestion under different conditions and CTC reduction were mastered,and the inhibition threshold was determined.Moreover,the response mechanism of anaerobic sludge to the toxicity of CTC was explained in order to find out the long-term effects of CTC on the mesophilic anaerobic digestion of chicken manure.The microbiological mechanism of effect of CTC on anaerobic digestion of chicken manure was clarified based on the analysis of microbial population structure.The theoretical basis was provided for the engineering application of anaerobic digestion of livestock manure contaminated by CTC.The main results were given follows:?1?Under batch experimental condition,the cumulative methane production increased with increasing of CTC concentration when the concentration of CTC was less than 20mg·L^-1.Gas production was inhibited when the concentration of CTC was more than 60mg·L^-1,and the inhibition rate increased with increasing of CTC concentration.The inhibition threshold of CTC on anaerobic digestion of chicken manure was 22.16 mg·L^-1?547.2 mg·kg^-11 by dry weight?.?2?Under continuous experimental condition,the concentration of CTC in the range of1.25-25 mg·L^-11 increased the gas production and organic matter removal rate during continuous anaerobic digestion of chicken manure,and the hydrolysis,acidogensis,acetogensis and methanogensis of chicken manure in continuous anaerobic digestion could be promoted to a certain extent.The maximum COD methane conversion and net potential energy were achieved when CTC was 10 mg·L^-1.The conversion of anaerobic sludge EPS from LB-EPS and TB-EPS to S-EPS promoted hydrolysis,and the removal of CTC as carbon source lead to increased methane production.?3?Under continuous experimental condition,the concentration of CTC in the range of50-100 mg·L^-11 inhibited the gas production and organic matter degradation of chicken manure during continuous anaerobic digestion,and the hydrolysis,acidogensis,acetogensis and methanogensis of chicken manure was inhibited,either.The minimum COD methane conversion and net potential energy were achieved when CTC was 100 mg·L^-1.The inhibition threshold of CTC on daily methane production was 29.90 mg·L^-1(598.0 mg·kg^-1by dry weight).Continuous experiments were carried out to domesticate microorganisms in the anaerobic digestive system of CSTR by adding CTC in stages,which improved its tolerance to CTC.?4?The removal rate of CTC decreased with increasing CTC concentration,and CTC adsorbed in solid phase increased significantly.When the concentration of CTC was 10-100mg·L^-1,the cumulative effect of continuous system was enhanced,which indicated that CTC was easy to adsorb in biogas residue,and the residual drugs posed a great threat to the environment.It needs further harmless treatment before it can be used as organic fertilizer.?5?The addition of CTC reduced the richness and diversity of microbial species in the mesophilic continuous anaerobic digestion system of chicken manure.Stenotrophomonas,Nocardioides and Sphingomonas,which were more resistant to CTC,were the dominant genus.The long-term operation of anaerobic digestion of chicken manure contaminated by CTC can improve the resistance of fermented microorganisms.