Enrichment And Stimulation Of Functional Microbes Of Denitrifying Anaerobic Methane Oxidation Process

Denitrifying anaerobic methane oxidation（DAMO）is a novel denitrification process,using methane as the sole electron donor under anoxic condition.It plays an important role in linking carbon and nitrogen biogeochemical cycles.In wastewater treatment,DAMO process could utilize methane generated from anaerobic digestion in situ to remove nitrate or nitrite,which may develop to a potentially energy-efficient and environmental-friendly wastewater treatment technology.However,limited by the extremely slow growth rate and weak metabolism activity of DAMO functional microbes,its application remained stagnant for a long time.In this work,DAMO function microbes had been successfully enriched.On this basis,the effects of environmental conditions on DAMO activity were investigated.Besides,iron oxides nanoparticles,electroactive bacteria and electro-assisted biotechnology（EABT）were applied to stimulate DAMO process.To further scientific understanding,their effect on the functioning of the microbial community were studied.Finally,a novel double membrane（membrane aerated-filtered）reactor was constructed to explore start-up strategy of DAMO technology,providing references for the further practical study of DAMO process.In this study,DAMO function microbes had been successfully enriched by membrane aerated reactor（MABR）with the abundance increased to 70%.The optimum cultivation temperature and pH were proven to be 35℃ and 7.5,respectively.Low nitrite concentration would restrain DAMO activity,whereas over high nitrite concentration（6.16 mmol/L）would inhibit DAMO process.DAMO activity increased with the increase of methane partial pressure.Magnetite nanoparticles and electroactive bacteria Geobacter sulfurreducens（G.sulfurreducens）were able to promote DAMO process.Magnetite nanoparticles improved the abundance of methane aerobic oxidation bacteria Methylomonas spp.and triggered synergistic effect between it and NC10 phylum bacteria.The supplement of G.sulfurreducens could increase the abundance of NC10 bacteria and led to a better enhancement under hydroxyl apatite（HAP）.Besides these approaches,EABT could also effectively enhance DAMO process.In single chamber bioelectrical reactor（BER）,the best stimulating effect was obtained at 1 V exerted with the denitrification rate increased to 1.81-fold.However,the enhancement could only be realized under continuous electrical exposure mode,rather than intermittent mode.In two chambers BERs,the denitrification rate of cathodes in carbon electrodes BER and iron-carbon electrodes BER respectively increased to 1.97 and 1.76-fold,while no improvement had been found in anodes.Given our goal of investigating DAMO technology,a novel membrane aerated-filtered reactor had been designed and constructed.High denitrification efficiency（96.8%） could be achieved after 60 d opertation under 15 mg NO₂^--N/L containing influent.Higher influent load of 22.4 mg/（L·d）was obtained respectively by two different means:decreasing hydraulic retention time and increasing influent nitrogen concentration.Decreasing hydraulic retention time was more effectively with the removal rate of 88.5%,which could be the start-up strategy of DAMO process.On the other hand,EABT was able to enhancing the DAMO process based on the membrane aerated-filtered reactor.The reactor was capable of rapid recovery from high influent load,with nitrite removal rate fficiency increased to 99.2%,under 0.5 V voltage.