Superior Tuning And Control (STAC), a real-time biological nutrient removal control for phased isolation ditch (PID) technologies from Kruger USA uses online monitoring of nitrate and ammonia to control the phase length in response to incoming loading. It monitors orthophosphate, aiding in the control of chemical dosing for phosphorus removal. Switching from fixed to variable-phase length control allows for continuous and automatic optimization of the alternating anoxic-aerobic pattern of BIO-DENITRO and BIO-DENIPHO plants. It has been proven at full-scale plants that effluent nitrogen concentrations can be significantly reduced by controlling phase durations based on real-time measurements of ammonia and nitrate. It allows for an overall plant improvement, resulting in lower average effluent total nitrogen, less energy consumption and the ability to increase treatment capacity. 919/677-8310; www.krugerusa.com.