Study On The Microbiology Mechanism Of Synergism Of Anammox And Denitrification In Landfill Bioreactor And Its Optimized Strategies

During the process of sanitary landfill treatment of domestic waste,it will produce leachate,which has complex composition and extremely high content of nitrogen.Especially the mature leachate landfill,in which organic matter is decomposed and C/N becomes imbalance,making it hard to remove nitrogen by traditional nitrification-denitrification.Anaerobic ammonia oxidation?Anammox?is a new means for nitrogen removal with no carbon source,and there exists certain complementarity with denitrification,which make it possible for the coordination for Anammox and denitrification during leachate treatment.In this paper,quantitative Polymerase Chain Reaction?Q-PCR?,Illumina MiSeq sequencing and 15N stable isotopic tracing methods were applied to study the effects of influent organic loading,BOD5/TN and NO₂-N/NH₄-N ratios on the combined nitrogen removal through denitrification and anammox.By selecting the suitable inoculation sludge source,we researched the effective strategies to start landfill bioreactors quickly.The conclusions were shown as follows:1.The results indicated that,for the influent organic loading of 0.02-0.07 m^-3/d^-1kg,BOD5/TN of 0.05-0.2,NO₂-N/NH₄-N of 0.5-1.5,the total nitrogen removal was above 90%for the optimum condition,that is,organic loading of 0.04 kg·m^-3·d^-1,BOD5/TN of 0.2 and NO₂-N/NH₄-Nof 1.0.2.The amoA?AOA?was the dominant gene in anammox process,while nirK was dominant in denitrification process.hzsA was found in large amount in the bioreactor with high nitrogen removal,and was directly proportional to the influent BOD5/TN.Sequencing revealed that the dominant genus in landfill bioreactor were Pseudomonas,Dechloromonly,Comamonas,Nitrosomonas,Candidatus Kuenenia and Limnobacter,with proportions of 1.4-2.5%,1.3-2.2%,0.05-2.0%,0.4-1.6%,0.05-1.8%and 0.7-1.3%,respectively.The quantity of Nitrosomonas was inversely proportional to the nitrogen removal efficiency,while the quantity of Candidatus Kuenenia was directly proportional to the nitrogen removal efficiency.According to the outcomes of CCA and RDA analyses,a positive correlation between influent BOD5/TN and anammox microorganisms existed,suggesting a significant influence of BOD5/TN on nitrogen removal?p=0.004?.Similarly,there was a positive correlation between NO₂-N/NH₄-N ratio and denitrification microorganisms,indicating that,for low organic loading,organic matters facilitated synergistic nitrogen removal through denitrification and anammox,and that the nitrogen removal by denitrifying bacteria was influenced by influent water quality.Therefore,regulating the influent water quality is feasible for improving nitrogen removal efficiency in bioreactor.3.Using the aged refuse as filler,which mixed with anaerobic activated sludge and the rate was 6%,could improve the effect of reactors quickly.The result showed that inoculation accelerated the denitrification efficiency of the reactor at the beginning of the operation,while shortening the time required for the reactor to be efficiently and stably operated.It did not improve the efficiency of the denitrification efficiency.Inoculation increases the number of denitrifying functional microorganisms in the reactor,and the increase in the number of nirS functional genes may provide an oxidant for the metabolism of Candidatus Kuenenia.Thus the efficiency of denitrification and anaerobic ammonium oxidation in the reactor are improved.But the highest number of anaerobic ammonium oxidation microbes is the control group reactor.After the operation of inflow optimization,the abundance of hzsA in the control reactor was about 30%at the highest,and the abundance of hzsA was about 3 times higher than that of the orthogonal experimental reactor.It indicates that the optimization of water quality in the reactor can promote the enrichment of anaerobic ammonium oxidized microorganisms in the reactor.4.Influent water quality had impact on the contribution of anammox in landfill bioreactor.Approximately 9%of the nitrogen removal occurred through anammox process for BOD5/TN ratio of 0.05,and 21.46%for BOD5/TN ratio of 0.2.The anammox process also accounted for approximately 10%of the total nitrogen removal in the bioreactor for NO₂-N/NH₄-N ratio of 0.5 in influent,and 20.72%for NO₂-N/NH₄-N ratio of 1.0-1.5.Anammox contribution rate of inoculated was lower than the control group,the inoculated group contribution rate was as high as 13%,and the contribution rate was as high as 23%in the control groupIn summary,the research of landfill reactor denitrification and anaerobic ammonium oxidation synergistic mechanism provides a theoretical basis for the actual operation of the water quality optimization.The results show that the control strategy of optimization can effectively improve the efficiency of the reactor and the contribution rate of Anammox.In addition,inoculation of sludge can effectively improve the reactor denitrification efficiency.However,the main factors determining the denitrification pathway is the type and quantity of the microorganisms in the reactor,so it is more important to select the appropriate source of sludge to regulate the denitrification pathway.