Analysis Of The Microbial Community And Reformence Of Simultaneous Nitrification And Denitrification In The Three-Stage Catching Bed Reactor

The research on removal rates of COD and total nitrogen in the simultaneousnitrification denitrification（SND） system were discussed using three-stage catchingbed reactor. Meanwhile, the succession of the microbial community in the biofilmand mixture was studied using PCR-DGGE and FISH technology in order to find thepathway of denitrification in biological contact oxidation system. Major findings wereincluded as follow:（1） The affect of3influent flow rate distribution ratios on the removal of COD、NH₄⁺-N was not obvious, the removal rates of COD and NH₄⁺-N were above90%;The affect of HRT was unconspicuous, the removal rates of COD and NH₄⁺-Nreached at89.5%and90.6%,showing that system has good ability in resistance toimpact load, and the removal efficiency of COD and NH₄⁺-N is stable in the system.（2） The removal efficiency of total nitrogen was changed by influent flowrate:The removal efficiency of TN reached at70.2%when influent flow rate was3∶4∶3; When influent flow rate was controlled in4∶3∶3，62.7%of average TNremoval rate was obtained；When influent flow rate was adjusted to5∶3∶2，theremoval efficiency of TN decreased to58.5%.（3） The succession of the microbial community which was changed largely astime goes on was highly diversity in the biofilm.According to denaturing gradient gelelectrophoresis （DGGE） analysis, the dominant bacterial community in the biofilmcould be mainly consist of5groups: β-proteobacteria （39%）,γ-proteobacteria（22%）,unclassified bacteria （17%）,α-proteobacteria （13%） and Actinobacteria （9%）.（4） The microbial community in biofilm and in the mixture is similar accordingto DGGE profile and UPGMA cluster analysis. According to DGGE analysis, thedominant bacterial community in the reactor could be mainly consist of5groups:β-proteobacteria （41%）, unclassified bacteria （21%）, γ-proteobacteria（17%）,α-proteobacteria （14%） and Actinobacteria （7%）. In addition, β-proteobacteriahad an advantage in numbers, which played an important role in the degradation ofCOD removal.（5） Nitrosomonas sp played an important role in oxidizing ammonia anduncultured Nitrospirae bacterium played major role in oxidation of nitrite in thesystem. Denitrifying bacteria like Pseudomonas. stutzeri had a strong denitrifyingeffect in the system.（6） The FISH analysis indicated that the microbial community which was evenlydistributed was density in the biofilm. Furthermore, AOB and NOB were found inbiofilm in different period, which have played major roles in oxidation of ammoniaand nitrite in the system.