Abstract: The influence of inorganic carbon(IC) on anaerobic ammonium oxidation(ANAMMOX) process was investigated by evaluating the nitrogen removal efficiency in an up-flow ANAMMOX reactor. Results show that the nitrogen removal efficiency decreases significantly when stop adding IC into influent water. The nitrogen removal efficiency recovers and increases gradually when the mass concentration ratio of influent IC to total inorganic nitrogen(TIN) is 0.2~0.4. Increasing the ratio from 0.4 to 1.0 cannot bring a better nitrogen removal efficiency. When a new reactor was started up with the ratio of 0.4， the achieved nitrogen removal efficiency comes up to 1.04kg·m^-3·d^-1 after 61days stable operation. The ANAMMOX bacteria in the new reactor present higher activity than that in the previous reactor. Results suggest that IC provides a suitable carbon source and plays a catalytic role in the ANAMMOX process. Sufficient IC is important to maintain the activity of ANAMMOX bacteria and the stability of the nitrogen removal efficiency. 0.4 is the optimal ratio in the influent for ANAMMOX process.

Key words: ANAMMOX, inorganic carbon(IC), nitrogen removal efficiency, the ratio of IC to TIN, waste water