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Operational cost saving while improving effluent quality - Optimising propeller and aerator configuration

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AerationActivated sludge

Case description

Our client Waterschap De Dommel was retrofitting the aeration system of their large WWTP in Eindhoven (NL). Further, that plat was facing increased oxygen levels near the inlet of the anoxic zone, leading to higher effluent nitrate. Instead of a risky and costly trial and error approach, the utility has chosen a structural CFD modelling approach to find the best solution. It led to good decision making with confidence.

Questions the utility had:

  • What would be the optimal placement of the new aeration system to maximise effluent quality?
  • Can we save energy?


We simulated 1 of the 3 identical bioreactors of the 750,000 p.e. WWTP in 3D. We applied our proprietary multiphase WWTP CFD model, integrating biokinetics, so besides flow patterns, we could accurately visualise oxygen and nutrient concentrations. 9 different scenarios were tested to optimise plant performance both in terms of performance and cost (operational or design changes and hybrid combinations).

Optimal aerator design in wastewater treatment plant


  • Three mixers could be switched off at certain flow rates, leading to less effluent nitrate and saving energy, while velocities were still high enough to prevent settling.
  • The optimal aerator configuration was found with the model and is currently being installed
  • The CFD model was proven to be very accurate (read full blog articles)

Full blog articles available: Part I, Part II

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