Identification And Nitrogen Removal Characteristic Of Two Heterotrophic Nitrification-aerobic Denitrification Strains

Two heterotrophic nitrification-aerobic denitrification strains,named as HY2and LY1, were isolated from the activated sludge of secondary sedimentation tank and sediment of landfill leachate,respectively.In the light of their morphological and physiological features as well as the16S rDNA sequences, HY2and LY1were identified as Acinetobacte sp. and Pseudomonas putida.Heterotrophic nitrification characteristics of HY2and LY1were examined. The two strains presented the ability of coinstantaneous removing of both organic and ammonia nitrogen.HY2removed78%NH4+-N and87%COD.LY1removed70%NH4+-N and92%COD. The removal efficiency of NH4+-N by strain HY2reached98%under the optimal conditions of pH=8.0,inoculation quantity of5%,oscillation speed of150rpm,C/N ratio of10,ammonia nitrogen concentration of50.0mg/L and culture temperature at30℃.The removal efficiency of NH4+-N by strain LY1reached86%under the same condition except for C/N ratio of8.The abilities of strain HY2to aerobic denitrify and remove COD were investigated when NO3--N was provided as the only nitrogen source.The removal efficiencies of NO3--N by strains HY2and LY1were90%and100%,respectively.At the same time, COD removal efficiencies of the two strains were also high and both reached90%. In the flasks containing NO2--N as the only nitrogen source，the NO2--N removal ratios of HY2and LY1reached75%and89%, respectively.Under the optimal conditions,the process of removing nitrogen was done.The results confirmed that63%removal of nitrogen was changed into gas out of the reaction systerm by strain HY2and32%was assimilated into the cells. Strain LY1changed66%removal of nitrogen into gas and assimilated30%into the cells. Besides the concentration of nitrogen which converted to nitrite and nitrate was not high during degradation.These results showed that simultaneous nitrification and denitrification was happened.The process of removing ammonia nitrogen was done by setting strain HY2in the biological aerated filter and the sequencing batch reactor in order to test the bioaugmentation ability for ammonia wastewater treatment.When the biological aerated filter was operated on the condition of aeration intensity of40m3/(m2·h) and HRT of12h,the indexes effluent reached the primary discharge standard for water pollutants from municipal wastewater treatment plant(GB18918-2002).In aerobic condition,the removal efficiencies of COD and TN by the sequencing batch reactor respectively reached85%and57%,when the reactor works smoothly.The results showed that simultaneous nitrification and achieved in the reactor. And the nitrogen removal efficiency of the activated sludge with bioaugmentation was significantly higher than that of the conventional activated sludge.