In the completely autotrophic nitrogen removal over nitrite (CANON) process, the nitrite-oxidizing bacteria (NOB) should be effectively suppressed or thoroughly washed out. In this study, the nitrate production and the structure of NOB community under different inorganic carbon (IC) concentrations were investigated using denaturing gradient gel electrophoresis (DGGE) in a membrane bioreactor (MBR). Results showed that IC decrease correspondingly lowered the nitrogen removal, and simultaneously induced the nitrate production by NOB. DGGE results indicated the IC deficit led to the biodiversity increasing of both Nitrobacter-like NOB and Nitrospira-like NOB. An equation fitted between the ratio of nitrate production to ammonia consumption ([Formula: see text]) and the ratio of influent IC to ammonia concentration ([Formula: see text]) indicated the influent [Formula: see text] should be controlled between 1.6 and 2.3 to ensure the stable operation of the CANON process. A small amount addition of organic material could be used as an effective strategy to suppress NOB when the [Formula: see text] ratio was not appropriate.
Keywords: CANON; Inorganic carbon (IC); NOB; Nitrobacter; Nitrospira.