Deammonification Using Separate Partial Nitritation and Anammox Reactors: Two Years of Testing at California's Largest WRRF

Two-stage deammonification system was investigated to achieve the nitrogen reduction strategy in Hyperion Wastewater Reclamation Plant (HWRP). This is a challenge associated with stable biological treatment at the high temperature and high COD/TKN ratios of thermophilic sidestreams which may inhibit ammonia oxidizing and anammox bacteria. In the test period, the air-lift granulation reactor (AGR) performed partial nitritation under aerobic condition and the anammox reactor converted ammonium and nitrite to nitrogen gas under anoxic condition. The AGR has achieved >3.7 kg-N/m3/d of nitrogen loadin rate (NLR) by controlling pH and air flux. During the test period, COD was reduced by 43% after the AGR process, contributing to the performance improvement of the anammox reactor. As a result, the anammox reactor has been operated over a long-period with an NLR of >3.0 kg-N/m3/day and achieved greater than 85% total nitrogen removal by adjusting residual nitrite concentration. The projected NLR based on the best operating results of each AGR and anammox reactor is estimated by >2.7 kg-N/m3/day. The results of this study showed that the two-stage deammonification system is applicable for high strength centrate from thermophilic anaerobic digester effectively than single-stage system. This study will be of great interest to those utilities seeking efficient sidestream treatment with the added functionality of AOB-bioaugmentation into the mainstream for sustainable holistic nutrient management.