Partial Nitrification in Sequencing Batch Reactors Treating Low Ammonia Strength Synthetic Wastewater

Sequencing batch reactors fed with low ammonium strength synthetic wastewater under C/N ratios of 0.5, 1.5, and 3.0 were used to investigate the transition from full to partial nitrification. Two strategies for establishing partial nitrification, aeration duration control and process parameter control, were compared. The effect of C/N ratio on nitrite accumulation was also evaluated. Results showed that partial nitrification established by controlling aeration duration presented better performance with higher nitrite accumulation. An increase of C/N ratio helped nitrite accumulation; however, non-filamentous bulking of sludge happened at high C/N ratio. Based on mass balances for nitrogen, results for nitrogen during full and partial nitrification were distinct from one another. For low C/N ratio, during full nitrification, almost 100% of NH4+-N was oxidized to NO3--N without nitrogen loss; however, nitrogen loss increased obviously during partial nitrification, which indicated that dissolved oxygen concentration and C/N ratio influenced nitrogen loss significantly during nitrification.