The growth and nitrogen metabolism of heterotrophic nitrification‐aerobic denitrification (HN‐AD) bacteria are affected by nitrite, but the mechanisms underlying this for strain Acinetobacter johnsonii EN‐J1 are unclear. In this study, the addition of 10 mg/L nitrite increased the reduction rate of ammonium by 1.0 mg/L/h, and 20 mg/L nitrite increased the reduction rate of nitrate by 3.9 mg/L/h. Compared with the control, the...