Denitrifying performances of an aerobic denitrifer, Pseudomonas chloritidismutans strain X31

Removal of nitrogen from wastewater is becoming more and more urgent owing to serious environmental and health problems caused by nitrogen pollution in wastewater. Conventional systems for the biological treatment of nitrogen-containing wastes are based on the principle that nitrification is an aerobic process, whereas denitrification is restricted to anoxic conditions. However, in recent years, it has discovered that dentrification may proceed at a substantial rate under aerobic conditions. Aerobic denitrification provides a new approach for nitrogen removal and could lead to a substantial reduction in the complexity and costs of wastewater treatment plants when compared to anoxic denitrification. In this study, a novel aerobic denitrifier, Pseudomonas chloritidismutans strain X31, was obtained from the activated sludge after domesticating, which had the high ability of nitrogen removal. The denitrification characteristic of the aerobic denitrifier, strain X31, was particularly studied in batch culture under aerobic condition. The results showed that dentitrification process of X31 mainly occurred in LOG phase of the strain and nitrogen gas was the major end product of denitrification by the strain. During the denitrification of X31, pH in the culture medium increased while OPR in the medium decreased. Moreover, strain X31 can co-respire by using nitrate or nitrite and oxygen as electron acceptor. Nitrite respiration was easier than nitrate respiration in the presence of oxygen, in both of which high nitrogen removal rate was achieved. Strain X31 was not sensitive to oxygen and had a higher tolerance of dissolved oxygen concentration than other aerobic denitrifiers reported previously. In the range of DO concentrations of 3.2-17.5mg/L, the strain can select nitrate as electron acceptor. When the initial nitrogen oxides concentration in the culture was about 150 mg/L, the aerobic denitrification rate of the strain was not affected by DO. It is more likely that there was a constitutive, periplasmic nitrate reductase present in the strain of X31, which makes a significant contribution to the corespiration of nitrate and oxygen.