The Isolation, Screening, Identification And Characterization Of Two Heterotrophic Nitrification And Aerobic Denitrification Bacteria

Heterotrophic nitrification and aerobic denitrification bacteria are a class of bacteria with ability of both heterotrophic nitrification and aerobic denitrification. The research on the impact of conditions to nitrification and denitrification efficiency is helpful to improve the efficiency of aerobic nitrogen remove. But few heterotrophic nitrification and aerobic denitrification bacteria have been isolated and the nitrogen removal efficiencies of these bacteria are low.In order to obtain stains with high heterotrophic nitrification and aerobic denitrification efficiency, 32 strains were enrichment and isolated from the biochemistry treatment pool of Datansha waste water treatment plant. Two strains named A1-1 and O-1 with high ability of heterotrophic nitrification and aerobic denitrification were selected from the 32 strains and were identified by taxonomic identification. The efficiencies of nitrification and denitrification were detected to study the impact of the nitrogen source, the carbon and nitrogen ratio and the temperature. The sucrose, fructose, citric acid, starch, methanol and glucose was used as carbon source one by one; the temperature was set as 15℃, 20℃, 25℃, 30℃, 37℃and 40℃; the carbon and nitrogen ratio was set as 2, 5, 8, 10 and 12. The characteristic of aerobic nitrification and denitrification reaction of two strains were studied in this paper.The strain A1-1 was identified by 16S rDNA to be a Pseudomonas stutzeri with a similarity of 100% and the strain O-1 was identified by 16S rDNA to be a similarity of 97% with Alcaligenes denitrificans. While maintaining the other conditions unchanged, A1-1 in the citric acid is most effective in the six kinds of carbon source. The nitrification efficiency is about 40% and the nitrogen removal efficiency is 80%. When the methanol is used as carbon source for nitrification and denitrification, the efficiency is the lowest. When the carbon source is citric acid, O-1 can nitrify and denitrify with most nitrification efficiency of about 27% and nitrogen removal efficiency of 40%. The nitrification and denitrification efficiencies of two isolates are higher than the nitrification and denitrification bacteria that have been isolated. The best temperature for nitrification and denitrification and growth of A1-1 bacteria is 30-37℃, the best temperature for O-1 is 25-30℃. The improvement of the carbon-nitrogen ratio can increase growth and nitrification and denitrification of two isolates. But when the carbon-nitrogen ratio is increased to more than 8, the impact of the carbon-nitrogen ratio to the nitrification and denitrification of A1-1 is smaller. The direct measurement method was used to detect the biomass nitrogen instead of estimation method of previous researchers. The biomass was obtained by centrifugation of bacterial suspension and the alkaline potassium persulfate digestion-uv spectrophotometric method was used to measure biomass nitrogen directly. Dry weight and the formula of bacteria were used to estimate the biomass nitrogen previously. The relationships between bacterial suspension absorbance and biomass nitrogen of the A1-1 and O-1 strains were also established bacterial nitrogen in the paper.