As part of an industrial commission the GECO►C team was charged with developing a load-dependent fuzzy control system for the Wietzendorf wastewater treatment plant and implementing it at the plant. The aim of the control system was to continuously determine the load situation at the plant – using the oxygen consumed within the intermittent zone.
From the calculated load situation, the intention was then for the optimised set values for the subordinate control to be determined by means of a corresponding evaluation within the fuzzy controller. In addition, the duration of the anaerobic phase was then be controlled using the kink, taking into account the redox potential.
Our team developed an algorithm which calculated the oxygen consumption based on the power of the fan and the measurement of the oxygen released. From the oxygen consumption the load factor for the plant could then be determined. Using this, with the aid of a fuzzy controller, the set values for the subordinate control system were calculated.
In addition, the trend of the redox potential was evaluated based on the presence of a kink, as an indication that the denitrification phase had ended, in order to determine the optimum duration for denitrification from this.
The use of the control system in practice showed a clear improvement in the control behaviour and, as a result, allowed the plant to be operated in a more stable way.
