From Wastewater Plant to Power Plant

Marselisborg WWTP produces 40 percent more electricity than it needs and 2.5 GW of heat.

Water and wastewater facilities are usually high energy consumers. Typically water and wastewater-treatment processes account for 25 – 40 percent of the municipality’s electricity bill – energy that can be saved and money that can be freed up and put to better use elsewhere. The answer lies in understanding that the technology and knowledge is available to make water-management systems energy neutral.

Our Marselisborg Wastewater Treatment Plant has increased plant efficiency and reduced energy consumption by optimizing all its processes. In 2016, the plant produced 40 percent more electricity than it needed and 2.5 GW of heat for the district heating system without adding external organic waste or carbon. This excess energy is enough to serve the needs of the drinking water supply and wastewater treatment facilities in the region.

Over the past five years, Aarhus Vand has put great focus on energy savings and energy production. At Marselisborg Wastewater Treatment Plant we have 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 1 GWh/year which corresponds to about 25 percent in total savings.

During the same time period, the energy production has been improved through the 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.

In 2015, Marselisborg WWTP had a total energy production of 9,628 MWh/ year and an energy consumption of 6,311 MWh/year, equivalent to a net energy production of 153 percent (2015) making it more than energy neutral. Most of the installed technologies have a payback time of less than 5 years.

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