Research Of Bioaugmentation Nitrogen Removal In Constructed Wetlands Via Heterotrophic Nitrification-aerobic Denitrification Bacterium

A heterotrophic nitrification-aerobic denitrification bacterium, N7, was isolated from activated sludge and was identified as Acinetobacter calcoaceticus according to its morphological characters, physiological, biochemical identification and 16S rDNA sequence analysis. With ammonium sulfate and sodium succinate as the sole nitrogen source and carbon source, respectively, the removal rate of ammonia nitrogen of the strain N7 was 99.2%, but the removal rate of total nitrogen was only 67.1%. The result suggested the strain N7 had a good heterotrophic nitrification effect. It also had a better effect of aerobic denitrification. The removal rate of total nitrogen was respectively 62.7% and 75.0% using potassium nitrate or sodium nitrite as the sole nitrogen source at 30℃ and 150 rpm. The experimental results showed that the optimum denitrifying condition was obtained at 30℃,230 rpm, C/N ratio of 35 and pH of 8.1.By using tissue culture method, reed seedlings were successfully obtained from the reed seeds. Selection reed seedling of growth was basically consistent and healthy, manual transplanting into the simulation of artificial wetland system. Through tracking monitoring on the 54 days of the constructed wetlands system, which found that it had a good removal effect on COD, TN, NH4+-N. The initial COD, NH4+-N and TN concentrations of plant systems were 400 mg/L,30 mg/L and 30 mg/L, and the removal rates were 65%～75%,69%～76%,50%～60%, respectively. It showed that microorganisms were gradually playing a role in the simulation of constructed wetlands system, and the system was running well.Simulation of artificial wetland system in a laboratory scale, using bioaugmentation technology, combined with the strains of N7, soil and plant, consisting of three different systems for the experimental comparison. Reed inoculated with the bacterial and soil (S group) in the phase I to the 7th day, the effluent COD, NH4+-N, TN were reduced to 45.7 mg/L,0.6 mg/L,0.8 mg/L, and the removal rate was 88.6%,97.9% and 97.2%, respectively. The results of experiments showed that the strain N7 can not only enhance the effect of nitrogen removal in simulated constructed wetland, but also promote the removal of organic substances. It has a good application prospects.Strain N7 has been existed in the constructed wetland system from the beginning to reaching the standard of strengthening, which indicates that the strain N7 and the Phragmites australis rhizospheric microorganisms have good symbiotic, and played a role in denitrification. Sequence analysis results showed that the main microbial populations in the constructed wetland systems were Acinetobacler calcoaceticus strain, Acidobacteria bacterium, Clostridium sp., Spirosoma sp., Nitrosomonas sp., Nitrospiraceae bacterium, etc., and most of them were uncultivate strains. In the two phases, Phragmites australis rhizosphere contains part of the same species, only the numbers of microorganisms have difference, but they also have some changes. So it showed that the enhancement experiment not to produce a great impact on the constructed wetland system of plant rhizosphere.