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.