Biological Nutrient Removal by Denitrifying Phosphorus Accumulating Organisms in a Continuous Flow, One-Biomass System

A Lab scale continuous flow system with Anaerobic/Anoxic/Aerobic configuration was set up to study the effect of oxygen in the internal recycle stream on the performance of denitrifying phosphorus accumulating organisms (DPAOs). It was found that by using a degas device the dissolved oxygen (DO) in the nitrate recycle stream was effectively decreased from 0.1±0.02 to 0.01±0.01 mg/L. This provided DPAOs favourable conditions to grow under anoxic condition, and thus successfully sustained in the system. When the degas device was removed from the system, the DO concentration in the anoxic reactor increased. The proliferation of DGAO population and deterioration of DPAOs performance was observed. The increased population of DGAO/GAO, which competed for the carbon source with PAOs, resulted in a poor performance of EBPR.