Effects of Cd(II) on nitrogen removal by a heterotrophic nitrification aerobic denitrification bacterium Pseudomonas sp. XF-4.

Simultaneous heterotrophic nitrification and aerobic denitrification (SND) is gaining tremendous attention due to its high efficiency and low cost in water treatment. However, SND on an industrial scale is still immature since effects of coexisting pollutants, for example, heavy metals, on nitrogen removal remains largely unresolved. In this study, a HNAD bacterium (Pseudomonas sp. XF-4) was isolated. It could almost completely remove ammonium and nitrate at pH 5-9 and temperature 20 ℃-35 ℃ within 10 h, and also showed excellently simultaneous nitrification and denitrification efficiency under the coexistence of any two of inorganic nitrogen sources with no intermediate accumulation. XF-4 could rapidly grow again after ammonium vanish when nitrite or nitrate existed. There was no significant effects on nitrification and denitrification when Cd(II) was lower than 10 mg/L, and 95 % of Cd(II) was removed by XF-4. However, electron carrier and electron transport system activity was inhibited, especially at high concentration of Cd(II). Overall, this study reported a novel strain capable of simultaneous nitrification and denitrification coupled with Cd(II) removal efficiently. The results provided new insights into treatment of groundwater or wastewater contaminated by heavy metals and nitrogen.