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In Germany, many wastewater treatmant plants are oversized. The increasing water-saving trends or the changing temporal use of the treatmant plants cause an inefficient energy consumption.

We simulate your treatmant plant and find a tailor-made solution for your problem.
Having years of experience, we know different possibilities such as the variation of the ventilation strategy, the use of stirrers or other alternative solutions.
Contact us, we answer your individual questions!


  • a detailed insight into the running processes
  • specification of the sewage sludge and the behaviour of the sewage sludge within the nitrification tanks
  • simulative determination of inefficient geometry variants
  • test possibilities of different configurations and solution approaches
  • high cost and energy saving


There are numerous possibilities to avoid the sedimentation of the sewage sludge in the nitrification tank. To find the optimal solution we need to model your treatmant plant first for analyzing the present circumstances in it.

After having done that, we calculate important values like the water velocity, the air content and whirl structures in the denitrification and nitrification tanks or time-dependent flows and simulate various scenarios and approaches.

The calculations and the simulation results inform us about the needed measures to optimize your treatmant plant.


The aim of the project Magdeburg was to find an alternative scenario for the treatmant plant because it spends a high amount of energy and there is no great need for an air/oxygen injection in the night.
The swimming sludge in the clarification tanks is kept in abeyance by the ventilation system and should not settle on the ground after turning it down. To guarantee that, we use stirrers setting the sludge into motion permanently. Therefore, we determinded a sedimentation criterion together with our customer, which says that there should be an extensive minimum speed of 19 m/s in the tank to avoid the sedimentation.

Step 1: Modeling of the tank and the stirrers / ventilation system
number of cells (tank): 2164947
Reconstruction of the stirrers in 3D using 2D drafts

Step 2: Definition of the geometry and linkage

Step 3: Calculation of 3 different scenarios with varied boundary conditions

*Wassereinlass = water inflow

Scenario 1: We turn off the ventilation in the tank and insert 10 stirrers.

In scenario 1, we inserted 10 stirrers with regular intervals and vertical positions in the tank and checked whether we can avoid the sedimenation with this modelling approach.

Modelling: bubble-water system

  • viscosity: 0.05 Pa.s
  • water inflow: 0.084 m/s
  • dry sludge content: 0.4 %
  • bubble size: 3 mm

The simulation graphic shows that the sewage sludge in the tank is not moved sufficiently. The sedimenation criterion is not fulfilled.

Scenario 2: We turn on the ventilation halfway and insert 4 stirrers into the other half of the tank.

In scenario 2, we changed scenario 1 and turned on half of the ventilation. In the other half of the tank, we positioned 4 stirrers every 10 meters (turned 15° towards the ground of the tank) with a higher rotational speed.

Modelling: bubble-water system

  • viscosity: 0.05 Pa.s
  • water inflow: 0.084 m/s
  • dry sludge content: 0.4 % (evenly distributed in the tank)
  • bubble size: 3 mm

This graphic demonstrates that the modification causes a little more movement in the tank but Magdeburg told us that the combination of ventilation and stirrers is not possible.

Scenario 3: We turn off the ventilation completely and insert 4 stirrers.

In scenario 3, we varied the entire modelling approach and used the stirrers as impulse sources. In this case, the sludge particles will be whirled up through the scaled pressure difference on the disks (our pulse sources) to avoid sedimentation.

Modelling: incompressible flow

  • viscosity: 0.05 Pa.s und 0.001 Pa.s
  • water inflow: 0.084 m/s
  • dry sludge content: effects only the presumed basic viscosity

This is the most efficient solution because we need only 4 stirrers to avoid the sedimenatation in the whole nitrification tank. The new offset arrangement and the used pressure ensure enough motion to avoid sedimentation.
According to this modelling approach, the sludge particles stay on the ground 5 minutes maximally before they get whirled up through subsequent whirls. Focusing on the colours of the graphic, we can see that the sedimentation criterion (minimum speed of 19 m/s) is fulfilled.

We have the ability to calculate and simulate various modelling approaches and different variants of them and thats why we find YOUR OPTIMAL SOLUTION!