Effect of Nitrite on Autotrophic Denitrification Efficiency by Pseudomonas sp. SZF15

The effect of nitrite on autotrophic denitrification was tested using mixed electron donors of Mn(II) and Fe(II) with Pseudomonas sp. SZF15. In batch experiments, nitrate and nitrite were completely depleted without ammonia production (denitrification rate of 0.151 mg-NO3−-N·L−1·h−1 and 0.104 mg-NO2−-N·L−1·h−1, respectively), suggesting that denitrification occurred by strain SZF15 via nitrite reductase. A maximum denitrification rate of 0.097 mg-NOX−-N·L−1·h−1 was found at an n(NO3−-N):n(NO2−-N) ratio of 5:5. Edwards and Aiba models were used to describe the denitrification inhibition caused by nitrite, and the kinetic parameters determined from the Edwards model were rmax of 2.148 mg-NO2−-N·g-VSS−1·h−1, KS of 6.225 mg-NO2−-N·L−1, and KI of 25.152 mg-NO2−-N·L−1. These results provide useful information for optimization of the autotrophic denitrification process by avoiding inhibition to obtain higher denitrification efficiencies. In addition, strain SZF15 showed excellent denitrification performance for groundwater treatment.