The Effect Of Livestock Breeding Wastewater Heavy Metals And Antibiotics On ANAMMOX Process

The treatment of livestock breeding wastewater is difficult due to its high nitrogen content and low C/N ratio characteristics.The traditional denitrification process is not efficient on this wastewater,so it is imperative to develop an efficient and economical treatment processes.The ANAMMOX process is an economical,low-consumption and high-efficiency denitrification process because it does not require an external carbon source and has high denitrification efficiency.However,due to the long generation and slow growth rate of AnAOB,the ANAMMOX process usually has a long start-up time,which restricts the extensive application of the ANAMMOX process.Therefore,the rapid start-up method of anaerobic ammonium oxidation is of great practical significance for its engineering application.In addition,AnAOB is extremely sensitive to the environment.The quality of livestock breeding wastewater has low C/N characteristics.In theory,the ANAMMOX process has unique advantages.However,the high concentration of antibiotics and heavy metals in the livestock breeding wastewater will affect the denitrification effect of ANAMMOX,and there are few studies on it.Therefore,the above practical application of the ANAMMOX process was investigated and the livestock breeding wastewater as the target.This study was aimed to provid a research basis for introducing the ANAMMOX process into the treatment of livestock breeding wastewater.The results were as follows:?1?The feasibility of rapidly starting the ANAMMOX reactor with low abundance storage of anaerobic ammonium oxidizing sludge was studied,and the operational strategy of the practical start-up ANAMMOX reactor was provided.The reactor observed ANAMMOX reaction in 6 d and the EGSB-ANAMMOX reactor was started in only 19 days by adding a part of the low-abundance storage ANAMMOX sludge,which was reduced by nearly 70%compared with using the anaerobic or nitrifying sludge as the inoculated sludge.After 100 d operation,the total nitrogen removal load was stable at 1.05±0.18 kg N/m³ d,and the NO₂^--N removal rate was stable at97.38±0.06%.The anaerobic ammonium oxidation rate of the enrichment was 5.73mg-N L^-1 h^-1 g vss^-1.The ratio of?NH₄⁺-N/?NO₂^--N was 1.24,which was close to the theoretical matrix consumption ratio of anaerobic ammonium oxidation.Howere,?NO₃^--N/?NH₄⁺-N ratio was 0.19,lower than the theoretical ratio 0.26 because the denitrifying bacteria existed in the system.The community structure in the reactor changed significantly.After 85 days,the community structure became single and the dominant microorganisms in the reactor were transformed from heterotrophic microorganisms to AnAOB.Based on phylogenetic tree,the AnAOB species in the system were Candidatus Brocadia fulgida,Candidatus Brocadia sinica,Candidatus Jettenia caeni,Candidatus Kuenenia stuttgartiensis,and their relative contents were14.64%,0.31%,2.94%,and 0.01%,respectively.In addition,the suspected new AnAOB species OTU32 was found to be closely related to the Candidatus Brocadia anammoxidans species,but further research is needed.?2?The inhibitory effects of typical heavy metals Cu²⁺,Zn²⁺and Cd²⁺on the ANAMMOX reaction in livestock breeding wastewater were studied.The results showed that the ANAMMOX reaction was inhibited by Cu²⁺,Zn²⁺,and Cd²⁺when they were added separately.The IC₅₀ values of the three heavy metals were 8.62 mg/L,20.24mg/L,and 20.22 mg/L,respectively,and the relative toxicity was ranked as Cu²⁺>Cd²⁺>Zn²⁺.The results of orthogonal combined inhibition test showed that the levels of Cu^2+,Zn²⁺and Cd²⁺were different when they were added,and the inhibition degree of anaerobic ammonium oxidation was different.Cu²⁺of the three heavy metals had the strongest inhibitory effect on ANAMMOX,flowed by Cd²⁺and Zn²⁺.?3?The inhibitory effect of typical antibiotics on the ANAMMOX reaction in livestock breeding wastewater was studied.The results showed that the inhibitory effect of chlortetracycline on anaerobic ammonium oxidation was obvious.The relative anaerobic ammonium oxidation rate decreased to 85.53%at 10 mg/L.The IC₅₀concentration was 87.89 mg/L by fitting the dose-effect curve,which is a low value of the current IC₅₀ of antibiotics for ANAMMOX.However,the inhibition of ANAMMOX was not obvious when the TylosinTartrate concentration range was 0-1280 mg/L,so the fitting curve could not be obtained.The IC₅₀ value of the antibiotic was not calculated.Different concentrations of levofloxacin hydrochloride had different inhibitory effects on ANAMMOX.With the concentration increased from 50 to 800 mg/L,the ratio of anaerobic ammonium oxidation rate was from 5.56.mg-N L^-1 h^-1 g vss^-1 decreased to1.67 mg-N L^-1 h^-1 g vss^-1,and the IC₅₀ of the half-inhibitory concentration was 529.34mg/L by fitting the dose-response curve.?4?Cu²⁺,Cd²⁺,and chlortetracycline with high toxicity were selected as the orthogonal tests factors.The combined inhibition effects of antibiotics and heavy metals on anaerobic ammonium oxidation were studied.After adding chlortetracycline,Cd²⁺,and Cu²⁺,the relative anaerobic ammonium oxidation rates were 24.37%-96.54%compared with the control group.Among the three inhibitors,Cu²⁺had a significant effect on the relative anaerobic ammonium oxidation rate.Cd²⁺had a significant effect on the relative anaerobic ammonium oxidation rate,and chlortetracycline had no significant effect on the anaerobic ammonium oxidation rate.There is no interaction between Cu²⁺and chlortetracycline in the three inhibitory factors.The effect of Cu²⁺and chlortetracycline on the anaerobic ammonium oxidation rate is independent,while the effect of Cd²⁺and chlortetracycline on anaerobic ammonium oxidation rate is antagonistic.Overall,this study puts forward the strategy of the rapid start-up of ANAMMOX process which can be used in the current project.The effects of heavy metals and antibiotics on the ANAMMOX process in livestock breeding wastewater were also studied,which was aimed to provide a research basis for the introduction of ANAMMOX process into livestock breeding wastewater.