[Influence of Phosphate on Nitrogen Removal Efficiency of ANAMMOX Sludge]

In this study, the effect of phosphate concentration on the nitrogen removal efficiency of ANAMMOX sludge was researched. The inhibition kinetic parameters were fitted and the abundance of ANAMMOX bacteria in the reactor before and after phosphate inhibition was analyzed by Real-time PCR. The short-term experiments showed that there was no significant effect on the nitrogen removal efficiency of ANAMMOX sludge when phosphate concentration was less than 30mg·L^-1. With the increase of influent phosphate concentration, the removal rate of nitrogen decreased rapidly. When the phosphate concentration was raised to 200mg·L^-1, the activity of ANAMMOX sludge reached a complete inhibition state. The parameters of phosphate inhibition were fitted by Haldane inhibition model. The half-inhibition constant was 70.1 mg·L^-1. The long-term results showed that when the phosphate concentration was less than 50 mg·L^-1, the effect on the nitrogen removal efficiency of ANAMMOX sludge was not significant. When the phosphate concentration reached 70-90 mg·L^-1, The activity of ANAMMOX sludge was obviously affected, and the stability could be restored after a certain period. Increasing the phosphate concentration had a more significant effect and resulted in a longer recovery time. Finally, when the concentration of phosphate reached 100 mg·L^-1, the nitrogen removal efficiency of ANAMMOX was seriously inhibited. The rate of nitrogen removal decreased from 158.33 g·(m³·d)^-1 to 60.17 g·(m³·d)^-1, resulting in 62% inhibition. The results of real-time PCR showed that the concentration of ANAMMOX was decreased from (9.97±0.86)×10⁷ cells·mL^-1 to (8.26±0.54)×10⁷ cells·mL^-1 in the restraining sludge system, and there was a relatively reduced trend.