At the beginning the primary focus for the WWTP Rottweil (50.000 EP) was on the improvement of nitrification and nitrogen removal. This was especially because of difficulties to keep the nitrogen concentration in the effluent below the legal binding values. The conditions for an optimization of the nitrogen removal looked promising due to a big anoxic volume in the activated sludge tank. However there needed to be a check to see whether the existing aeration system was suitable for implementing optimized control strategies.
Besides of the operational optimization, H2Office attempted to optimize the energy efficiency of the plant at the same time.
In a first step a dynamic simulation of the plant was conducted. Therefore the measured influent loads were checked with mass flow balances and compared with results based on estimated values for population and industry connected with the plant.
The calibrated model served to develop different optimization measures, to show their effects in detail and to select the best strategies for short, middle as well as long term application.
In the second stage the selected strategies have been realized. The most important modification was to combine the pre-denitrification with simultaneous nitrification-denitrification. To do so, the aeration system including the control and regulation strategies had to be renewed beforehand. H2Office was responsible for planning and supervision of implementation.