Traditionally, water and wastewater treatment processes account for 25 – 40 percent of the municipal electricity bill in Aarhus, Denmark. At the Marselisborg wastewater treatment plant, management and operations wanted to try and reduce that number and find ways to reuse energy, too.


The goal was to carefully define and optimize all processes to find savings. In addition, the project would ramp up efforts to capture and reuse the energy produced during wastewater treatment and use that as a source of green energy that could serve all other wastewater treatment facilities in the region. 


To accomplish the goals, energy-saving technologies like an advanced SCADA control system, a new turbo compressor, sludge liquor treatment based on the anammox process, as well as an optimized fine bubble aeration system were implemented. 

At the same time, energy production was improved through the deployment of energy efficient biogas engines (CHP), resulting in an increase in electricity production of approximately 1 GWh/year, which, according to the, is enough to power about 876,000 households annually. A heat exchanger was installed with the aim of selling surplus heat to the district heating grid, which amounted to approximately two GWh/year.


Since 2013, the project has resulted in a reduction in power consumption of approximately 1 GWh/year, which is equal to a 25 % reduction in power consumption. 

At the same time, energy production has increased significantly. The plant now produces 50% more energy than it consumes. This excess energy is enough to serve the energy needs for the whole water cycle, from drinking water production, to distribution, to collection and treatment of wastewater.