Two-Stage Partial-Nitritation/Anammox Process Demonstrates Stable and Efficient Treatment of High-Strength Industrial Digestate

This paper presents data from two and a half years of pilot testing which demonstrate performance of a two-stage deammonification configuration in treating high-strength reject streams from industrial co-digestion. In order to minimize inhibition by free ammonia (FA), the volumetric exchange rate of the air-lift granulation reactor for partial nitritation (PN-AGR) was limited to 40-50% for each reaction cycle. The PN-AGR was operated between 137 mg-NH3/L (at the start of the react cycle) and 7.8 mg-NH3/L (at the end of the react cycle), and the moving-bed biofilm reactor for Anammox (A-MBBR) was kept at a temperature of 35℃ and pH of 7.5. Accordingly, average FA concentrations in the A-MBBR were limited to 6.6 mg-NH3/L, preventing inhibition. The two-stage AMX® process, consisting of the PN-AGR followed by the A-MBBR, achieved significantly higher NLR (average 1.42 kg N/m3d) and NRR (average 1.26 kg N/m3d) than common single-stage PN/A processes, despite high influent concentrations of nitrogen, solids, salinity and COD. This process also achieved COD, SS and TN removal efficiencies of 82%, 89% and 89%, respectively, without pretreatment or dilution for over two years, under fluctuating influent quality. This supports the use of a two-stage deammonification process for treatment of high-strength reject streams from industrial co-digestion.