Optimal conditions and nitrogen removal performance of aerobic denitrifier Comamonas sp. pw-6 and its bioaugmented application in synthetic domestic wastewater treatment.

To assess the possibility of using aerobic denitrification (AD) bacteria with high NO₂^--N accumulation for nitrogen removal in wastewater treatment, conditional optimization, as well as sole and mixed nitrogen source tests involving AD bacterium, Comamonas sp. pw-6 was performed. The results showed that the optimal carbon source, pH, C/N ratio, rotational speed, and salinity for this strain were determined to be succinate, 7, 20, 160 rpm, and 0%, respectively. Further, this strain preferentially utilized NH₄⁺-N, NO₃^--N, and NO₂^--N, and when NO₃^--N was its sole nitrogen source, 92.28% of the NO₃^--N (150 mg·L^-1) was converted to NO₂^--N. However, when NH₄⁺-N and NO₃^--N constituted the mixed nitrogen source, NO₃^--N utilization by this strain was significantly lower (p < 0.05). Therefore, a strategy was proposed to combine pw-6 bacteria with traditional autotrophic nitrification to achieve the application of pw-6 bacteria in NH₄⁺-N-containing wastewater treatment. Bioaugmented application experiments showed significantly higher NH₄⁺-N removal (5.96 ± 0.94 mg·L^-1·h^-1) and lower NO₃^--N accumulation (2.52 ± 0.18 mg·L^-1·h^-1) rates (p < 0.05) than those observed for the control test. Thus, AD bacteria with high NO₂^--N accumulation can also be used for practical applications, providing a basis for expanding the selection range of AD strains for wastewater treatment.