Rapid start-up of anammox reactor using granular sludge supported on activated carbon

The long start-up time and high demand of anaerobic ammonium oxidation (anammox) limit the practical applications of the anammox process. In this study, granular sludge supported on activated carbon (AC) was used as seed sludge. The start-up time of the reactor was substantially shortened, and the expanded granular sludge bed (EGSB) reactor could be started quickly (in only 17 days). The nitrogen load rate (NLR) increased from 0.61 kg m-3 d-1 to 1.19 kg m-3 d-1, the removal rate of total nitrogen (TN) increased from 78.04% to83.15%, and the final ratio NH4+: NO2-: NO3- was 1:1.33:0.30. Moreover, in the gas analysis phase, the reactor load could be further improved and increased to 1.70 kg m-3 d-1 from the 18th–22nd day, and the reactor run stably. During this period, N2O and CO2 production was 0.8% and 0.02%, respectively. According to the analysis of microorganisms, the main functional microorganism in the reactor was Candidatus Kuenenia. The content of Candidatus Kuenenia increased by 5.45% after the reactor was started successfully. The color of sludge was brick red. This showed that the operation mode and inoculated sludge employed in this study are highly effective for the fast start-up of an EGSB reactor.