Nutrient sensor based real-time on-line process control of a wastewater treatment plant using recirculation

A new generation of sensors for on-line measurement of nitrate, ammonium and phosphorus has been used for process control in a pilot-scale plant. The pilot plant is designed for nitrogen removal using the recirculation principle for pre-denitrification. It has been shown that the supply of oxygen and recirculation of activated sludge to the denitrification tank can be controlled directly by a simple control routine using an on-line measurement of nitrate and ammonium in the aeration tank. There is potential for implementing biological phosphorus removal, when the level of nitrate in the recirculated sludge can be monitored on-line.