[Effect of Ni(Ⅱ) on Anaerobic Ammonium Oxidation and Changes in Kinetics]

Anaerobic ammonium oxidation (ANAMMOX) is widely used for treatment of ammonium-rich wastewater because of its economic and environmental benefits. However, ANAMMOX bacteria are sensitive to environmental conditions, especially to heavy metals. The short-term and long-term effects of Ni(Ⅱ) on ANAMMOX were studied by batch and continuous flow experiments, respectively. Results showed that low concentrations of Ni(Ⅱ) had promoted nitrogen removal by ANAMMOX and high concentrations inhibited ANAMMOX performance during a short-term period. Compared with the specific anaerobic ammonium oxidation activity (SAA) without Ni(Ⅱ) addition, SAA with 1 mg·L^-1 Ni(Ⅱ) addition increased by 11.14% and the SAA with 100 mg·L^-1 Ni(Ⅱ) addition reduced by 49.55%. The IC₅₀ of Ni(Ⅱ) for ANAMMOX was determined to be 83.86 mg·L^-1. In contrast, long-term Ni(Ⅱ) addition significantly suppressed nitrogen removal of ANAMMOX, and the suppression threshold of Ni(Ⅱ) on ANAMMOX was 15 mg·L^-1. The Monod model was applied to simulate the kinetics of ANAMMOX without Ni(Ⅱ) addition. The q_max0(TN/VSS) and K_S0 values were 12.25 mg·(g·h)^-1 and 405.36 mg·L^-1, respectively. The modified Haldane model was suitable to describe the kinetics of ANAMMOX with 50 mg·L^-1 Ni(Ⅱ) addition. The q_max(TN/VSS), K_S, and K_i values were 6.78 mg·(g·h)^-1, 313.2 mg·L^-1, and 1.32, respectively. The inhibition of ANAMMOX by Ni(Ⅱ) is anticompetitive inhibition. In addition, the inhibition of Ni(Ⅱ) on ANAMMOX was mainly related to the content of intracellular Ni(Ⅱ). The IC_{50intracellular Ni(Ⅱ)}(VSS) of intracellular Ni(Ⅱ) was 0.072 mg·g^-1.