Study On Denitrification Removal Of Nitric Oxide And The Microbial Community Structure In Biotrickling Filter

Nitrogen oxides(NO_x)are major atmospheric pollutants.Biofiltration was a widely adopted method for air pollution control due to its green safty and lower operating costs.In this thesis,denitrificaion purification of waste gases containing NO was preliminarily investigated in biotrickling filter (BTF).The removal and transformation process of NO in BTF would be explored,and then,the microbial community structure of BTF would be described.The results showed that rapid start-up of BTF could be aehieved by using gas-liquid phase joint inculation.The biofilm in the biotrickling filter became mature within 9d at room temperature with the NO inlet concentration of 160 mg/m³,pH at 7 to 8,spraying volume of 0.43 L/h and the empty bed residence time(EBRT)of 113s.In the ten-months' steady operation,NO removal efficiency(RE)maintained 60.4%～98%,averagely 79.2%,with NO concentration of 165～581 mg/m³,EBRT of 30～120s,. With and without nitration addition,NO max elimination capacity(EC) were 32.2 g/m³Â·h and 23.6 g/m³Â·h,respectively.It shows nitration is a key factor for NO denitrification.Process parameters,such as NO inlet concentration,spraying volume, EBRT and oxygen concentration,had effects on the NO removal efficiency. BTF maintained better elimination capacity with spraying volume of 0.43 L/h.With the increase of oxygen,denitrifying bacteria were subject to different degrees of inhibition,which caused RE of NO decreased.In the NO denitrification,NO would be decomposed into N₂,with the intermediate of nitrous oxide(N₂O).Nitrate and pH were the important factors influencing NO removal and N₂O production.Nitrate improved the growth of NO denitrifying bacteria and increased RE of NO.However, overuse of nitrate resulted in the accumulation of N₂O.When pH was 7.5, BTF maintained the good performance with less N₂O production.The experimental results of PCR-DGGE indicated that,the bacteria species with stable microbial community structure in BTF were Spirochaetales,Actinobacteria,β-Proteobacteria.The differences between the microbial community structures at different packing hights existed obviously.The biodiversity in the lower part of packing were more abundant than the higher part of packing media.And the similarity between the lower and middle part of packing media was 76.5%.After adding nitrate,new bacteria species respiring nitrate appeared,such as Thauera sp. 53,Flexibacter canadensis,Photobacterium profundum SS9. Simultaneously,when the amount of nitrate increased largely,BTF could maintain stable microbial community structure.