Nitrogen Removal And Microbial Community Structure In A Pre-denitrification Biofilter

A pre-denitrification biofilter was constructed based on traditional A/O processwith2-6mm volcanic to further enhance the effectiveness of pre-denitrificationwastewater treatment system. The paper discussed the performance under theinfluence on ammonia load and nitrification liquid reflux on nitrogen removal andthe law of contaminants removal of the system from point of view of both processand microbiology to get the optimum process parameters and the mechanism ofnitrogen removal and the relationship between microbial communities and thechanging process parameters, which intended to provide theoretical reference fortreatment process development.Pre-denitrification biofilter successfully started up with inoculum of activatedsludge from secondary settling tank of municipal wastewater treatment plant after31days, when dense biofilm formed on the surface of media. At this time, thesystem achieved the COD, ammonia, total nitrogen removal rates of77.45%,97.32%and59.90%with stable effulent quality. The optimum ammonia load of thesystem was0.170kg·m-3·d-1with average effluent concentrations of45.38mg·L-1,1.73mg·L-1,13.47mg·L-1and average COD, ammonia, total nitrogen removal ratesof71.23%,94.18%,51.13%. The optimum reflux ratio of the system was100%withaverage effluent concentrations of44.85mg·L-1,1.43mg·L-1,13.19mg·L-1andaverage COD, ammonia, total nitrogen removal rates of74.64%,94.49%,50.77%.The quality of effluent water is up to A in the first level in the Discharge Standard ofPollutants for Municipal Wastewater Treatment Plant (GB18918-2002).Results of16S rDNA library showed that pre-denitrification biofilter had agood microbial diversity. The microorganisms in the biofilm of pre-denitrificationbiofilter could be divided into ten groups, including Proteobacteria, Firmicutes,Actinobacteria, Bacteroidetes, Verrucomicrobia, Nitrospirae, Chlorobi,Planctomycetes, Acidobacteria, Gemmatimonadetes. The analysis of microbialcommunities TRF spectrum of biofilm in different stage indicated a closerelationship between the structure and succession of microbial communities and theperformance of nitrogen removal of the system. The total nitrogen removal achieveda best result under the ammonia load of0.170kg·m-3·d-1, when the communitystructure were the most complex and much denitrifying bacteria could be detected.The ammonia removal achieved a best result under the ammonia load of0.127kg·m-3·d-1, when a nitrifying bacteria Candidatus Nitrospira defluvii was detectedonly in this stage.