Screening and identification of aerobic denitrifiers and the optimization of denitrification conditions

Aerobic denitrifying bacteria were isolated directly from the aquaculture water,sludge and rural rivers.Following characterizing the phylogeny of the strains with the highest denitrifying capability,the effects of carbon source,C/N ratio,initial pH,inoculation quantity,rotational speed and temperature on the characteristics of denitrification were studied.The results showed that 35 strains of aerobic denitrifiers were obtained by primary screening on plates of Bromothymol Blue medium.One strain named GC5,which had the highest denitrifying capability was identified after secondary screening and was designated as Pseudomonas sp.based on the analysis of 16S rDNA sequence and phylogenetic analysis.Furthermore,the optimum conditions for denitrification were as follows: carbon sources ethanol,C/N ratio 15∶1,inoculation quantity 1%,initial pH 7.5,rotational speed 160 r·min-1,and temperature 30℃.Under such condition,the removal rate of nitrate nitrogen and total nitrogen in simulation sewage were 99.19% and 53.83%,respectively.