Steady-state modeling and evaluation of partial nitrification-anammox (PNA) for moving bed biofilm reactor and integrated fixed-film activated sludge processes treating municipal wastewater

The partial nitrification-anammox (PN/A) process can remove nitrogen from wastewater by converting approximately half of the ammonium to nitrite by ammonium oxidizing bacteria (AOB), followed by converting the remaining ammonium and nitrite to N-2 by anammox bacteria. Both the MBBR and IFAS processes can achieve the PN/A process in a single-stage reactor under appropriate operation. In this study, steady state simulation using SUMO (TM) was conducted to investigate the effects of key parameters (DO and COD/N ratio) on the PN/A process in both MBBR and IFAS. Results showed that MBBR and IFAS achieved about 90% total nitrogen removal by PN/A process with energy-efficient aeration and low COD/N ratios when treating domestic wastewater. IFAS achieved optimal nitrogen removal with lower DO concentration whereas MBBR showed better nitrogen removal at low COD/N ratio. Biomass concentration and process rates indicated that partial nitrification occurred throughout the biofilm of MBBR but mainly in the activated sludge of the IFAS.