Abstract
Single-stage Nitrogen removal using Anammox and Partial nitritation (SNAP) was demonstrated under continuous-treatment conditions to be reliable and stable. An average ammonium conversion of 89.2 ± 6.2% and a nitrogen removal of 76.3 ± 7.2% were obtained for 60 days of continuous operation under operational conditions of 35℃, pH 7.5~7.8, and 0.06~0.10 vvm aeration rate at a loading of 0.6 kg－N/m3/d using a simulated landfill leachate as influent. The observed sludge yield of the SNAP process was calculated to be as low as 0.045 mg－VSS/mg－N removed. The SNAP sludge had a particle size distribution of 420~550 μm and showed a tendency to form aggregates inside void spaces of the net-type acryl-resin biomass carrier. Specific ammonium oxidizing activities of the sludge ranged from 430 to 610 mg－N/g－VSS/d and 32 to 51 mg－N/g－VSS/d under total aerobic and anaerobic conditions, respectively. Levels of ammonium oxidizers and nitrite oxidizers were determined to be 107~109 MPN/g－VSS and 106 MPN/g－VSS, respectively. DNA analysis of the SNAP biomass revealed the existence of three dominant groups of bacteria including ammonium oxidizers closely related to Nitrosomonas europaea, nitrite oxidizers closely related to Nitrospira sp.; and anammox bacteria closely related to strains KU2 and KSU－1. These bacteria were suggested to exist in a dynamic equilibrium.
