In this study, a sequencing batch reactor (SBR) was used to achieve advanced nitrogen removal by simultaneous Anammox and denitrification processes. During the entire experiment, the Anammox microorganisms aggregated in the reactor as wall growth. Nitrogen removal was improved due to the reduction of nitrate, and the maximum total nitrogen (TN, including ammonia, nitrite and nitrate nitrogen) removal efficiency of 97.47% was obtained at C/N of 2. However, the sequentially increased organic matter resulted in a poor TN removal performance due to the suppression of Anammox. Fortunately, the Anammox activity completely resumed quickly after stopping dosing organic matter. PCR analysis results revealed that the Anammox bacteria gene copy number was not significantly reduced during the inhibition, which might explain the quick recover. (C) 2014 Elsevier Ltd. All rights reserved.