Semi-nitritation process producing optimum influent for anammox process in treatment of domestic wastewater

The process of anaerobic ammonium oxidation (Anammox) requires a proper ratio of NH4+-N and NO2−-N in the influent, which is difficult to control upon treating domestic wastewater. In this study, a control strategy of semi-nitritation (SN) process based on monitoring the pH profile and NH4+-N concentration in a sequencing batch reactor (SBR) was developed. The aeration time of each cycle in SN-SBR was calculated using the established equation tSN=tCOD+0.56αnS0/(S0−Sn). To verify the suitability of the control strategy, SN-SBR was operated continuously for 20 cycles, fed with real domestic wastewater with a fluctuating COD of 200-400 mg L−1 and NH4+-N of 65-80 mg L−1. The nitrogen removal performance of SN-anammox system using the developed control strategy was also monitored. Results showed that SN-SBR was able to generate a suitable ratio of NH4+-N to NO2−-N for the following anammox process, the TN removal rate of the SN-anammox system achieved 91.7 ± 0.4% and the average ammonium, nitrite and nitrate concentration of effluent was only 0.50 ± 0.24, 0.13 ± 0.09 and 4.9 ± 0.22 mg L−1, respectively. This study has potential application in the treatment of domestic wastewater using combined SN-anammox process.