Characterization Of An Aerobic Denitrifying Isolate And Studying On Its Potential Application In Wastewater Treatment

Human activity has greatly altered the nitrogen cycle on Earth over the past few decades, with major effects on both human health and the ecological functioning of natural ecosystems, particularly coastal marine systems where nitrogen is now the largest pollution problem. Although Nitrogen is essential for life, it can also serve as a pollutant if too much enters the ecosystem or is converted to a form that is not readily used. Nitrogen, among other things, was identified as a pollutant contributing to low dissolved oxygen conditions. These low dissolved oxygen conditions are referred to as hypoxia, consequence of eutrophication. The presence of nitrogenous substances in wastewater discharges has attracted attention because of the role of nitrogen in eutrophication of receiving waters. To prevent eutrophication, biological denitrification, as a new effective way, has been used in removing nitrate from wastewater.The purpose of this study is to isolate aerobic denitrifying bacteria which will be applied to wastewater treatment facilities and to eutrophication prevention for enhanced nitrate and nitrite removal. In our research results, a bacterium strain HS-N-2a isolated from hoggery activated sludge near Huazhong agricultural university was found capable of aerobic denitrification. The effect of different inoculated amounts of pre-culture was analyzed. The denitrifying rates of this strain under aerobic were compared. The result indicated that the rate was almost not affected by the presence of oxygen. More than 90% of 10mM nitrate was removed within 32 hours by this strain in the specific medium. During denitrifying process, nitrite was always kept in very low level. The denitrification potential of this bacterium was evaluated for treating artificial wastewater under fully aerobic conditions. Main biochemical and physiological features of this strain were characterized. The 16S rDNA sequence was compared with the published data in GenBank by using BLAST. The similarity to Pseudomonas stutzeri is 98%. These results proved that the strainHS-N-2a was a new strain belonging to the species of Pseudomonas stutzeri. Significance and impact of the study: strain HS-N-2a is highly promising for future potential application in-situ piggery wastewater treatment.