Inhibition Of Ammonia Nitrogen On Methanogens And Anaerobic Reactor Microorganism Community Succession With The Increase Of Organic Loading

Anaerobic methane fermentation is influenced by operating variables such as ammonia and organic loading.Ammonia nitrogen exists in large amount in poultry manure and landfill leachate,and hydrolysis of nitrogen-containing organic matter.Anaerobic methane fermentation is a series of complicated anaerobic fermentation system constituted by bacteria and archaea of which the dynamic equilibrium adjustment in each biochemical stage is of great significance.An accumulation of acidification product in fermentation system may result from problems for the microorganism running in high loading,which manifests in the unstability of anaerobic system caused by the activity decrease of methanogens.The current researches of the inhibition of ammonia nitrogen on anaerobic fermentation process mainly focus on the concentration of ammonia inhibition,type of substrate and reaction condition.It is complexity of detection the mcrA gene in these cases.Due to little information is available about the response of the organic loading to the anaerobic methane fermentation system and the dynamic change detection of microbial population.Therefore,this experiment was performed using the biochemical methane potential assay combining with the modified Gompertz model.The emphasis of this research is the feedback of ammonia nitrogen to the mcrA gene,the functional gene of methanogens and specific enzyme in ammonia inhibitory concentration level.Meanwhile,deeply analysis and combing are conducted on the structure change of microbial community at the organic loading improvement stage.The aim of the present study is to find simple and direct judgment method of methanogens of ammonia inhibition and reveals that the structure change of microbial community at the organic loading improvement stage in the anaerobic methane fermentation system.The main research content and research results are as follow:1.Taking saccharification wastewater as substrate by batch experimental,the paper investigates the biological methane potential?BMP?of different concentration level of organic wastewater in anaerobic fermentation process making use of Gompertz model combined.The results show that the corrected Gompertz model can be well used in the description of the saccharification wastewater fermentation and methanogenesis process.The R² of Gompertz model ranges between 0.981 to 0.994,approximate to 1.The actual CH₄ yield accumulated in each experimental group and the predicted value deviation of fitting equation are both within 4%,which shows that the model can well predict the growth of anaerobic microorganism under the change of organic concentration.2.Under the basis of organic wastewater BMP verification,the paper selects the functional gene mcrA of methanogens and the enzyme Co-M specific to the CH₄production process and explores the discrepancy of mcrA and Co-M when inhibited at ammonia nitrogen,especially free ammonia level.The research results show that:the maximum CH₄ yield R_max all decreases with the increase of FA inhibitory concentration and the lag time?increases with the increase of inhibitory concentration.The gene copy number of mcrA of methanogens and the concentration of Co-M significantly reduce with the increase of FA concentration,showing significant correlation?P<0.05?.Therefore,Co-M can be selected as the biological indicator for the quick detection of methanogens under the inhibition of ammonia nitrogen.3.In the EGSB reactor,the influence of gradient improvement stages of OLR and anaerobic methane fermentation reactor is investigated.The research results shows the COD removal rate,methane productivity is decreased gradually.The content of VFA in effluent,ratio of VFA/COD,particle size of granules are increased gradually in contrast.The VFA in effluent is composed of acetic acid and propionic acid in all stage of the experiment.The organic loading of?13.73±1.16?g-COD/?L·d?is the control value determining the stability of the anaerobic system.Meanwhile,the author suggest that the ratio of VFA/COD serve as adjudicator for stability in anaerobic fermentation reactor.The anaerobic system can be running stable when is below 0.4.4.Through Illuminahigh-throughput sequencing platform,the paper analyzes response of the community structure of bacteria and archaea to the cascade change of OLR in the anaerobic methane fermentation system and determines the dominant microorganism species in different loading stage.The result of the sequencing reveals that the species abundance of flora and the community diversity in the EGSB reactor.The community distribution of microorganism in all stages show differences in bacteria and archaea.The diversity of biocenosis is gradually increase with OLR in EGSB reactor.There are 23 common phylum in all samples.The relative abundance in dominant phylum of Bacteroidetes,Proteobacteria and Firmicutes are increased,but the phylum of Euryarchaeota is decreased.There are 42 common class in all samples,12 in which are dominant.The relative abundance in dominant class of Bacteroidia,Clostridia and Gammaproteobacteria are increased,but the class of Methanomicrobia and Deltaproteobacteria are decreased.There are 23 common genus in all samples.The relative abundance in dominant genus of Bacteroides and Desulfovibrio are increased,but the genus of Geobacter,Methanolinea and Methanosaeta are decreased.In addition,the relative abundance in dominant genus of Methanobacterium,Methanolinea,Methanosaeta and Methanospirillum are decreased with the increase of OLR.