| High concentration of NH4+ is major problem in the pollution treatment of swine wastewater. Heterotrophic nitrification bacterium could effectively removed nitrogen pollution in the environment because of its denitrification characteristics that oxidated nitrogen oxide into nitrate nitrogen. This paper dealt with the isolation and denitrification characteristics of a heterotrophic nitrification bacterium which isolated from the high NH3-N swine wastewater. Based on the screening methods published by some scienctists, an isolating method in the study was put forward to used an acetamide as a sole carbon and nitrogen source to screen a heterotrophic nitrifying bacterium from the swine wastewater. An efficient heterotrophic nitrification bacterium was isolated and identified with 16S rDNA sequence. The phylogenetic analysis of the strain was performed based on the 16S rDNA sequence. The efficiency of heterotrophic nitrification was identified for the strain. The strain FJAT-14899 was identified to be P. denitrificans with the aid of 16S rDNA sequencing.24 strains with denitrification characteristics were enriched and isolated from the swine wastewater of different locations, which were analysed to get the information on molecular polymorphism of heterotrophic nitrification bacterium by the technology of REP-PCR^ BOX-PCR and ERIC-PCR. Amplification bands were clear and obvious difference between the bands. The cluster analysis based on genetic fingerprint showed that similar strains were be clustered and the molecular differences between heterotrophic nitrifying bacterium was obvious.P. denitrificans FJAT-14899 had a higher removal rate of NH4+-N with promissing application in swine wastewater treatment. The removal rates for the total concentrations of nitrogen and NH4-N were 81.7% and 53,7% in 12 h cultural time. The final removal rates of the total nitrogen and NH4+-N were 90.1% and 61.3% after 24 h culturing without accumulations of nitrite nitrogen and nitrate nitrogen. Under laboratory conditions, studied the effect of various factors on the nitrogen removal characteristics. More inoculation quantity, the higher the nitrogen removal efficiency, but in low quantity of 0.01%, still achieved good denitrogenation effect after 20 h culturing; Maximum tolerance value on ammonia nitrogen was 600 mg.L1; The best conditions of denitrification characteristics was the C/N 8, pH 8-9, T= 35℃. Under this condition, P. denitrificans FJAT-14899 removal rate of NH4+-N was 90.8%, and removal rate of total nitrogen was 59.5%.Compared with the immobilizated effects of P denitrificans FJAT-14899 with different methods, the results showed that under the conditions of 3% sodium alginateã€3%CaCl2 and 18 h, the immobilized pellets had the best performance. Studied on ammonia nitrogen removal characteristics of immobilized bacteria, the result demonstrated that free state removed nitrogen needed shorter time than immobilized pellets. But in the practical swine wastewater, immobilized bacteria showed good removal characteristics, swine wastewater that the initial NH4+-N concentration of 382.7 mg.L-1, treatmented 24 h, the removal rate of NH4+ -N was 68%. |
