Study On Microbial Diversity And Denitrification Mechanism In A Sequential Batch Bioreactor Landfill

Sequential batch bioreactor landfill is an innovative landfill technology, in whichthe leachate through ex-situ nitrification and in-situ denitrification to achieve nitrogenremoval. However, the microbial diversity and denitrification mechanism in asequencing batch bioreactor landfill were rarely reported in the related references.This paper focused on the biological nitrogen removal procee during the processof garbage stabilization by establishing a sequential batch bioreactor landfill unit in anexperiment scale.Molecular technology of high-throughput sequencing and functionalgene cloning library were used to analyse the changes of the microbial communitystructures, especially the community structure and distribution of main microorganisminvolved in the nitrogen removal. Combined with the leachate quality to explore theprossible pathway of nitrogen removal in the landfill reactor from the perspective ofmolecular ecology, and attempted to further analyze the production mechanism ofN2O.1. In the sequential batch bioreactor landfill, both in the fresh refuse reactor andthe aged refuse reactor, the concentration of N2O was in a low level at first, andincreased in the later period of the experiment. The concentration of N2O from theaged refuse reactor based on nitrification was higher than that from the fresh refusebased on denitrification.2. The microbial community in the sequential batch bioreactor landfill wasanalyzed by high throughput sequencing. The obtined results indicted that the mostdominant phylum in the aged refuse reactor based on nitrification changed fromProteobacteria、Bacteroidetes to Firmicutes、Proteobacteria. Meanwhile, the mostdominant phylum in the fresh refuse reactor based on denitrification unchaged, themost dominant phylum was still Firmicutes、Bacteroidetes. Moreover, Euryarchaeotabacteria were found in the fresh refuse reactor, which indicted that there existedmicrobial methane in the fresh refuse reactor. 3. Clone library analysis showed that the majority of ammonia oxidizing bacteriain the aged refuse reactor was unknown bacteria, presumably to be Nitrosomonasbacteria. The diversity of denitrifying bacteria in fresh refuse reactor is abundant,which mainly included Thauera and Thiobacillus of β-Proteobacteria. Additionally,one group of denitrifying bacteria may be classified as Bradyrhizobiaceae of α-Proteobacteria.4. Analysis of the distribution and quantity of nitrifying and denitrifying bacteriain the reactor landfill indicted that the aged refuse reactor existed ammonia oxidation,nitrification, heterotrophic denitrification, aerobic denitrification and other relatedprocess, as well as potential anammox. Meanwhile, the analysis also indicted that thedominant process in the fresh refuse reactor were heterotrophic denitrification,autotrophic denitrification.The denitrification intensity has weakened compared withthe previous both in the fresh refuse reactor and the aged refuse reactor.5. The amount of nitrifying bacteria in aged refuse reactor rose in the later periodof the experiment, which enhanced the nitrification and increased the concentration ofnitrate.While the amount of denitrifying bacteria decreased, resulting in incompletedenitrification and N2O instead of N2becoming final product of the denitrification,and therefore the production of N2O rose. For the fresh refuse reactor, theconcentration of nitrate in the recirculated leachate rose, while the the amount ofdenitrifying bacteria reduced, resulting in the increase of N2O produce in the laterperiod of the experiment.