[Identification and Nitrogen Removal Characteristics of the Heterotrophic Nitrification and Aerobic Denitrification...

Nitrogen removal by a newly discovered Pseudomons sp. strain, DK1, isolated from activated sludge was investigated. Using glucose as a carbon source and a n(C)/n(N) ratio of five, batch experiments showed that the aerobic denitrification removal rate was 4.09 mg·(L·h)^-1 and 4.43 mg·(L·h)^-1 with NaNO₃ or NaNO₂, respectively. Completely nitrogen removal was achieved when using these two nitrogen sources. DK1 was also found to heterotrophically remove NH₄⁺ -N at a rate of 2.32 mg·(L·h)^-1 and to carry out anoxic denitrification of a range of concentrations of NO₂^- -N (from about 100 to 300 mg·L^-1) within a maximum of 36 hours of inoculation. In the presence of both NO₃^- -N and NO₂^- -N, DK1 was found to preferentially denitrify NO₃^- -N. Simultaneous nitrification and denitrification (SND) capacity of the DK1 strain was observed when using ammonium and nitrate or ammonium and nitrite and the corresponding nitrogen removal rates reached as high as 95.06% and 94.69% within 30 hours of inoculation, respectively. Ammonium with both nitrate and nitrite resulted in a 100% nitrogen removal within the same time frame. The ability to achieve SND and to denitrify both NO₃^- -N and NO₂^- -N makes the DK1 strain potentially useful for future application in nitrogenous wastewater treatment.