Modelling of the Ostend WWTP (Belgium) for energy consumption reduction

The plant with high levels of instrumentation and control was modelled to explore possibility to further reduce energy consumption.
At the WWTP of Oostende, operated by Aquafin, an advanced aeration control is installed, based on online measurement of oxygen in the carrousel and of both nitrate and ammonium at the effluent of the activated sludge tanks.

As the plant meets the discharge limits at all times, a model was set up in WEST to evaluate the possibilities to reduce the energy consumption of the plant.

The model was calibrated and resulted in good agreement with the available data of daily aeration energy consumption. Monthly averages agree with differences around 5% and never more than 10%. The same conclusion could also be made for total energy.
A scenario analysis on the aeration controller settings (based on DO, NH4 and NO3 on-line sensors) revealed that an energy saving up to 5.5% can be obtained. Total nitrogen would slightly deteriorate (effluent NH4 increases but NO3 decreases). So, it is clear that – as the plant already has an advanced aeration controller – no gain in energy consumption can be achieved without giving up on effluent quality, and that an optimum combination of set-points can be selected whether energy or effluent consents are the target.