Nitrifying bacteria addition into reactors operating near washout conditions for nitrification

Abstract

Sequencing batch reactors, at 10 degrees C, operating near the minimum solids retention time (washout conditions) for nitrification, were seeded daily with nitrifying biomass acclimated to 10 and 20 degrees C. Effluent NH3-N levels were decreased to less than 5 mg/L within 23 d for both seeding regimes. Once seeding was terminated, the reactor seeded with nitrifying bacteria acclimated to 10 degrees C continued to achieve full nitrification, whereas the reactor seeded with nitrifiers acclimated to 20 degrees C saw a rapid increase in effluent NH3-N concentrations. Nitrification was not completely lost in the latter reactor after seeding was stopped for 30 d.