Advanced computer control based on real and software sensors

The introduction of state-of-the-art on-line meters is the first step towards achieving more intelligent operation of wastewater treatment plants as the directly involved parameters are known. The use of these on-line measurements is dependent on the reliability of the data, which is the control system STAR, Superior Tuning and Reporting, is secured by DQC, Data Quality Control. With reliable measurements combined with selected operational data, it is possible to identify process relations and implement on-line control strategies such as those performed by STAR today in oxygen set point control, intermittent aeration control and recirculation control. Some of the STAR control functions are based on a certain kind of calculations described as software sensors, where information is achieved from qualified data and statistical data handling. Software sensors give an improved basis for on-line control strategies. These model-based “sensors” are available in an advanced process control systems such as STAR. The results compiled at the Sydkysten WWTP show that the introduction of STAR control affords larger economies than expected. Today, the amount of energy consumed at the plant has been reduced by 30% and the dosing of carbon for denitrification by 100%. The economies achieved run into approx. DKK 470,000 per year and the new expense relating to the operation and maintenance of meters is, by comparison, DKK 55,000.