Turning wastewater into green energy and achieving 150% energy self-sufficiency at Marselisborg WWTP

2 September 2020

Solution provider

Aarhus Vand is a utility situated in the second largest city in Denmark at Aarhus Bay. We supply and treat water for 350.000 people. Aarhus Vand strive to obtain the most sustainable water cycle through innovation and international partnerships

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Challenge

Traditionally wastewater has been considered a problem but on the contrary it can be a valuable resource from which we can recover energy, chemicals, nutrients and other valuable resources. However, while wastewater treatment plants are big energy consumers, Marselisborg Wastewater Treatment Plant has been transformed from an energy consumer to an energy producing plant.

Solution

At traditional wastewater treatment plants, the energy produced is nowhere near enough to cover the operation of the plant but in Aarhus it is. Marselisborg WWTP has an energy self-sufficient far above 100 percent and the plant is in fact a power station, a bio refinery where energy is produced from wastewater. Production of energy from wastewater is no new invention. However, it is new that a wastewater treatment plant can produce as much as 150 – 160 percent energy based on normal household wastewater.

Result

The plant produces enough energy to cover 94 percent of all the energy used for the whole water cycle in the catchment area. 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 proces and optimised the fine bubble aeration system.

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. 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.

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

A 3VAND partner
We are an active partner in 3VAND – a strategic collaborative partnership consisting of the leading water utilities in Denmark: HOFOR, BIOFOS, Aarhus Vand and VCS Denmark.