COMBINING AERATED-ANOXIC AND UCT PROCESSES FOR BIOLOGICAL NUTRIENT REMOVAL – LESSONS FROM A FULL-SCALE STUDY

This study was a full-scale investigation of the benefits and limitations of implementing aerated-anoxic conditions in a UCT variation process. Two treatment trains were used; one was modified to include the aerated-anoxic section in the UCT variation process while the other remained unmodified and served as a control of normal operation. The modified treatment train had a modest increase in total nitrogen removal (from 52% to 63%) and a slight deterioration in effluent ammonia levels, although the latter was caused by an increased flow into the modified treatment train rather than the creation of aeratedanoxic conditions. The results of AOB population dynamics, monitored using an amoA-based terminal restriction fragment length polymorphism (TRFLP) method suggested that the aerated-anoxic condition maintained the N. europaea lineage AOB population, presumably due to its high affinity for oxygen. In addition to nitrogen removal, the study also demonstrated that including an aerated-anoxic section in a UCT process does not negatively affect phosphorus removal. Although not sufficient for significant nitrate removal, the aerated-anoxic UCT combination can be implemented in full-scale if organic substrate distribution for both phosphorus and nitrogen removal is optimized. Perhaps the most significant benefit of this proposed configuration is the potential savings in aeration cost.