| Methanotrophs can use methane as the only carbon source and energy sourcey to effectively remove nitrogen in the oxidation,which can be divided into aerobic methane oxidation coupled to denitrification?AME-D?and anaerobic methane oxidation coupled to denitrification?ANME-D?,and thus,they are of vital significance in the researches of carbon and nitrogen cycles.With great practical potential of AME-D in deep denitrification of tail water in urban sewage plants,the methane required is renewable energy and can be produced by the anaerobic treatment process of sewage treatment plants.In this study,two deep denitrification systems?reactors A and B?based on AME-D were constructed for the nitrogen pollutants in the tail water of urban sewage treatment plants.The construction method of the system was studied,and the main control factors on the system efficiency were investigated.Based on this,the tail water of a sewage treatment plant in Guiyang was studied,and the functional groups of the organic matter in and out of the water were analyzed by Infrared and Raman spectra,using 16S rRNA gene sequencing technology and metagenomic technology to analyze the microbial diversity and functional genes in the system,and explore the mechanism of action of this deep nitrogen removal system.,explore the effect of this technology on the removal of antibiotics and endocrine in actual sewage.The main conclusions of the study are as follows:?1?Constructed the AME-D system in intermittent operation code.The average total nitrogen concentration in the effluent of the reactor A can reach 1.32 mg·L-1,the average removal rate is 93.4%,and the average total nitrogen concentration in the effluent of the reactor B can reach 1.53 mg·L-1,with an average removal rate of92.35%.The optimal methane intake ratio of the system is 3%,and it can achieve good deep nitrogen removal at 20-30?.Infrared and Raman spectroscopy analysis showed that the peaks caused by NO3-symmetrical stretching in both the A and B reactors disappeared significantly,and the peaks were significantly enhanced by the absorption of alcohol COH out-of-plane bending or C-H out-of-plane bending vibration,and A and B reactors can effectively remove nitrogen pollutants in the water,and the intermediate products formed by the oxidation of methane may be mainly alcohols,amides and esters.?2?The results of 16S rRNA gene sequencing showed that both nitrifying bacteria,denitrifying bacteria and aerobic methanotrophs were present in the reactors A and B.At the completion of the construction,the methanotrophs in the reactor A weremainlyMethylocystis?0.27%?,Methylosarcina?0.10%?and Methyloparacoccus?0.12%?,the denitrifying bacteria were mainly Pseudomonas?56.92%?,Paenibacillus?3.52%?and Lysinibacillus?3.00%?,the nitrifying bacteria were mainly Nitrospira?0.1%?;the methanotrophs in the reactor B weremainlyMethylosarcina?0.30%?,Methylocystis?0.13%?and Methylocaldum?0.09%?,the denitrifying bacteria were mainly Pseudomonas?23.43%?,Lysinibacillus?4.77%?and Paenibacillus?2.43%?,and the main nitrifying bacteria were Nitrospira?0.35%?.After the study of the main influencing factors,the relative abundance of the main functional bacteria changed,the methanotrophs in the reactor A were mainly Methylosarcina?0.13%?,Methylocaldum?3.38%?and Methylocystis?1.12%?,the denitrifying bacteria were mainly Pseudomonas?0.38%?and Hyphomicrobium?3.60%?,and the nitrifying bacteria were mianly Nitrospira?0.38%?;the methanotrophs in the reactor B were mainly Methylosarcina?1.84%?,Crenothrix?0.14%?and Methylocystis?1.9%?,the denitrifying bacteria were Hyphomicrobium?1.19%?and Pseudomonas?0.61%?,and the nitrifying bacteria were mainly Nitrospira?0.42%?.It shows that the AME-D denitrification system of A and B reactors is realized by the cooperation of methanotrophs,denitrifying bacteria and nitrifying bacteria.?3?Through the research on the tail water of a town sewage treatment plant in Guiyang,it is known that the system has a higher nitrogen removal effect.The ammonia nitrogen in the inlet water is 0.7mg·L-1,the total nitrogen is 9mg·L-1,and the average total nitrogen concentration in the effluent of the reactor A is 0.90mg·L-1,the average removal rate is 89.95%,the average total nitrogen concentration in the effluent of the reactor B is 0.96mg·L-1,and the average removal rate is 89.28%;Infrared and Raman spectrum analysis proves that the AME-D system can achieve better denitrification,and the incoming and outgoing water contains alcohol?possibly an intermediate product formed by the oxidation of methane?.It was found that the A and B reactors had obvious removal effects on 8 antibiotics such as tetracycline,ofloxacin and sulfadiazine,and had no removal effect on di-n-butyl phthalate.?4?Further analysis by metagenomic technology showed that both nitroso-bacteria,nitrifying bacteria,denitrifying bacteria and aerobic methanotrophs were present in the reactors A and B system's microorganisms and functional genes.There were 15 species of methanogens in the reactor A,the mainly were Methylobacter?0.52%?,Methylomonas?0.39%?and Methylocaldum?0.25%?,there were 9 species of denitrifying bacteria,the mainly were Terrimonas?4.74%?,Flavobacterium?1.42%?and Pedobacter?0.51%?,the nitrifying bacteria were mainly Nitrospira?1.38%?and Nitrobacter?0.03%?,the nitroso-bacteria were Nitrosomonas?0.07%?and Nitrosospira?0.06%?.There were 15 species of methanogens in the reactor B,the mainly were Methylobacter?1.63%?,Methylomonas?1.06%?and Methylosarcina?1.01%?,there were 8 species of denitrifying bacteria,the mainly were Flavobacterium?0.62%?,Pedobacter?0.23%?and Rhizobium?0.25%?,the nitrifying bacteria were mainly Nitrospira?2.97%?and Nitrobacter?0.02%?,the nitroso-bacteria were Nitrosomonas?0.11%?and Nitrosospira?0.09%?.Metagenome functional annotation found that 67.5%of the genes in reactor A were related to microbial metabolism.The most abundant type of metabolism was amino acid and its derivative metabolism,accounting for 14.17%,membrane transport accounting for 3.63%,and exogenous material organisms,Degradation accounted for 2.55%.Reactor B of the genes were related to microbial metabolism accounted for 68.25%,the most abundant type of metabolism is also amino acid and its derivative metabolism,accounting for 14.23%,membrane transportation accounted for 3.68%,exogenous substances biodegradation It accounts for 2.56%.Functional genes related to nitrification,denitrification and methane oxidation appear in the reactors A and B,including functional genes of aerobic ammonia oxidase,nitrate reductase,nitrosate nitrogen reductase and denitrifying enzymes,particulate methane monooxygenase?p MMO?,soluble methane monooxygenase?s MMO?,methanol dehydrogenase and functional genes that oxidize methane to formaldehyde,etc. |
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