Over the past five years, the water utility Aarhus Vand has put great focus on energy savings and energy production.
At its Marselisborg WWTP, the utility has implemented energy-saving technologies such as an advanced SCADA control system, a new turbo compressor, sludge liquor treatment based on the anammox process, as well as optimised the fine bubble aeration system. This has resulted in a reduction in power consumption of approximately 1GWh/year which corresponds to about 25% in total savings. During the same time period, the energy production has been improved through implementation of new energy efficient biogas engines (CHP), resulting in an increase in electricity production of approximately 1 GWh/year. Furthermore, a new heat exchanger has been installed with the aim of selling surplus heat to the district heating grid, which represents approx. 2 GWh/year. Between 2015 and 2019, Marselisborg WWTP had an average total energy production of 9.6 MWh/year and an energy consumption of 6.4 MWh/year, equivalent to a net energy production of 150%. Most of the installed technologies have a payback time of less than 5 years.