The Westewitz wastewater treatment plant (WWTP) is located between Dresden and Leipzig in Germany. The plant is a role model for small WWTPs (German plant size class 1-2). Despite its size, the plant is well positioned and equipped to demonstrate the energy saving or even energy supply it could provide the municipality. By adapting processes and existing technologies to the Westewitz WWTP, project partners will enhance the carbon extraction and the nitrogen removal. This case study will set the basic steps to achieve positive waste water treatment plant.

The potential for energy savings or even energy supply by the municipalities should not be neglected for smaller plant sizes; suggested processes and technologies can be adapted to specific constraints with no need of high maintenance efforts. The carbon extraction and the nitrogen removal will be at stake through this case study as they are key in developing energy positive waste water.

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  • Enhance carbon extraction
  • Demonstration of treatment goals (especially nitrogen removal)
  • Demonstration of control scheme
  • Demonstration of energy balance
  • Transfer to operation personnel
  • Duckweed pilot plant
  • Enhanced carbon extraction
    • Measured by biogas yield (bio-methane tests)
  • Demonstration of treatment goals (especially N-elimination)
    • Measured by conventional chemical test kits and compared to the gained results before the new installation
  • Demonstration of the control scheme – stable and safe (remote control and online monitoring)
  • Demonstration of energy balance
    • Measured by energy consumption and compared to the previous treatment results
  • Transfer to operation personnel (reduced operation costs, savings in aeration & substrate)
    • Measured by cost calculations
  • Duckweed pilot plant (Full stream nitrogen und phosphorus elimination)
    • Measured by chemical test kits
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Nowadays, carbon extraction is achieved at a rate of 30% in the primary settler. The enhanced extraction of carbon POWERSTEP is aiming for is very important to reach the objective of “energy-positive” wastewater treatment plant. The C-source is important to gain biogas out of the wastewater and the more C-source you get the higher the biogas yield at the end of the day. Therefore, an enhanced biogas production means less energy needs for water treatment.

But an increased carbon extraction challenges nitrogen removal, given the dependence of denitrifying bacteria on an easily accessible source of carbon. The current method used to remove nitrogen is performed by activated sludge. Under the POWERSTEP project, nitrogen will be removed through advanced control of the activated sludge and with a compact duck-weed reactor. This technology has not been demonstrated for municipal wastewater treatment so far, emphasising the challenging and innovative character of the project.

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Local Associated Partners

At Westewitz, POWERSTEP project partners rely on the support of:


POWERSTEP Project: Veolia Drumfilter function from Arctik sprl on Vimeo.

Johan Stüber, Berlin Technical University from Arctik sprl on Vimeo.



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