BIODIVERSITY IN ACTIVATED SLUDGE THROUGH BIO-AUGMENTATION: INCOPORATING NITRIFIERS FROM TREATMENT OF HIGH-STRENGTH, ELEVATED TEMPERATURE RECYCLE STREAMS

A bench-scale study was undertaken to evaluate the potential to reduce the required SRT for nitrification through bio-augmentation of main-stream reactors using treated anaerobic digester supernatant. Performance measurements of ammonia and nitrite oxidation and characterization of reactor communities using techniques from molecular biology have been made. There is evidence from 120 days of reactor operation that bio-augmentation will increase nitrification stability in main-stream reactors. Reactors receiving bio-augmentation have exhibited greater stability than a control reactor not being bio-augmented, maintaining ammonia oxidation throughout the experiment. Conversely, the control reactor lost ammonia oxidation for an extended period. In addition, results obtained from restriction length polymorphism (RFLP) analyses of the amoA gene strongly suggest that the operation of the side-stream reactors influences the composition of the ammonia-oxidizing bacteria (AOB) community; the AOB seeded into the main-stream system persist; and bio-augmentation results in a significant change in the composition of the AOB community over time.