Isoloation And Characteristics Of Aerobic Denitrifying Bacteria

Amount of acid rain in China have undergone an almost exponential increase over thepast decade and become the world’s third largest acid rain area after Europe and NorthAmerica. Anthropogenic emissions of nitrogen oxides (NOx), which are mainly producedduring the burning of fossil fuels, have negative effects on ecosystems and contribute to theformation of acid rain. In China NOx are mainly emitted from coal-fired power plants. Thebiological removal of NOx from contaminated gas streams by biofilters is efficient low-costNOx abatement technologies with no second-pollution, but the flue gas discharged fromcoal-fired power plantsis estimated to contain typically3~8%(v/v) O2, which had negativeeffect on traditional denitrifying process. In order to eliminate these drawbacks in biofilters,the technology of novel aerobic denitrifying bacterial, which were cultured and inoculated inbiotrickling filter to ascertain oxygen effects on NOx removal, is meaningful.A bacterial strain CP1with high nitrogen removal efficiency was isolated from biofilmof the biotrickling filter of a coal-fired power plant, which by adopting specific culturemedium and dilution flat purification. The isolate was identified as Pseudomonas aeruginosathrough morphological feature, biochemical characteristics and16SrDNA gene homologyanalysis. The bacterium can be synthesized as the gene napA of the periplasmic NAR underaerobic conditions.Studied on its function of aerobic denitrification at the temperature of30oC, the resultsshowed that nitrate in the culture media were be efficiently removed from136.87mg/L to2.06mg/L, and the nitrogen removal efficiency was up to98.49%in24hours, and no nitritewas observed at last. During the denitrification of strain CP1, the percentage of total nitrogenlost was estimated to be32.3%and the pH in the culture medium gradually increases.The studied on factors affecting aerobic denitrification by strain CP1showed that themost suitable C/N for aerobic denitrification was12, and the temperature was30oC~40oC.By using sodium citrate and succinate, the nitrogen removal rate of CP1was more than90%.The change of DO did not influence the effect of denitrification when it varied from0mg/L to11.2mg/L. Strain CP1can respire by using ammonia nitrogen or nitrite as nitrogen source andachieve high nitrogen removal rate.The development of a biotrickling filter (BTF) system to inoculate a newly isolatedstrain of CP1for the effective treatment of NOx is described. When the inlet NOconcentration was500ppm and the concentration of oxygen was8%, the removal efficiencyof NOx was estimated to be90%. The BTF system was able to consistently remove80~91.7% NO when the inlet NO was500ppm in an oxygen stream of2~20%which means oxygen hadno negative effect on removal efficiency. The NOx removal efficiency of BTF system wasproportional to the EBRT, as the lengthen of EBRT, NOx removal rate increased and then tendto be stable. The gene of nitric oxide reductase and nitrous oxide reductase was analyzed bymeans of PCR amplification and sequencing. Results manifested that the bacterium can besynthesized as norB and nosZ gene.