Rapid and stable achievement of mainstream nitritation at low temperature using the competitive inhibition caused by the organics.

The unstability of mainstream nitritation at low temperature has always been a limiting factor for the nitrogen removal from domestic wastewater by anammox. In this study, the competitive inhibition caused by the organics has been demonstrated as an effective strategy to rapidly and stably achieve mainstream nitritation. This strategy was based on our novel discovery that nitrite-oxidizing bacteria (NOB) was more susceptible to the organics inhibition than ammonia-oxidizing bacteria (AOB). Batch tests showed while NOB activity gradually decreased by 66.5%, AOB activity only decreased by 31.6% with the initial C/N ratio raising from 0.0 to 3.0. Furthermore, treating the actual domestic wastewater at 14-18 °C, mainstream nitritation was rapidly established within 12 days and then the nitrite accumulation ratio was stable at ∼92.1% during a long-term operation. This strategy could be easily and effectively applied in urban WWTPs through modifying the operation mode.