| Nitric oxide (NO) is a major source of atmospheric pollutant. The traditional technologies for NO removal are expensive and easy to produce secondary pollutant. So autotrophic biofilter have become the better choice to treat the NO.After accumulation of nitrobacteria from activated sludge in medium with nitrite as the only nitrogen source, one nitrobacteria strain N-20 which showed high nitrifying rate (75.10% after 16 days) was isolated on the separation plate. After detection of appearance, physiological and biochemical characteristics, growth characters, it was identified as the strain belonging to Nitrobacter Genus according to Bergeys Manual of Determinative Bacteriology (8th). It was named as Nitrobacter sp. N-20.Nitrobacter sp. N-20. was inoculated on the surface of carbon foams (24ppc, 18cpp) and lava to form biofilm. After two months, the biofilm formed and got dynamic balance with the highest nitrifying rate reaching 260mg/L d in the inoculation basin. The NO2- removal efficiency of three different packing in liquid phase reached 94 %~98%, 23 %~45%, and 15 %~21%, respectively. In gas experiment, the results show that the 24PPC (Pores Per Centimeter) Carbon Foam-based biofilter had the greatest performance of NO removal. A steady removal efficiency of 48%~74% wasattained for the 24PPC carbon foam-based biofilter at specified NO influent concentrations of 61.5~123.0mg/m3 and an EBRT of 3.5minutes. The other two biofilters have low performance results.Finally, GFP(green fluorescent protein) gene was applied to mark E.coli JM 109. The GFP-marked cell was then inoculated on the surface of lava to develop biofilm. The fluorescent image stacks of different layers at given area covered with biofilm were gotten by CSLM (confocal scanning laser microscopy, CSLM). Then quantifying parameter of biofilm was acquired through COMSTAT program, such as: biomass, average thickness, maximum thickness etc. These parameter could correctly reflect the spatial structure of biofilm.
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