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Marselisborg – a wastewater treatment plant in Denmark's second largest city, Aarhus
Marselisborg generates surplus power from wastewater treatment

The project

Water and wastewater treatment facilities are normally the single largest electricity consumer for a municipality. Typically, water and wastewater treatment processes account for 30–50% of the municipal electricity consumption. The high consumption is related to the energy intensive processes but also its continuous operation cycle, 24/7 and 365 days annually. Since 2010, Aarhus Water has worked intensively together with water environment consultants to improve the energy balance for the Marselisborg wastewater treatment plant.

The solution

As part of an intensive energy-efficiency optimization program, VLT® drives were installed on almost all rotating equipment at the Marselisborg wastewater treatment plant, including blowers, pumps, mixers and dewatering pumps.

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We have always specified Danfoss VLT® frequency converters specifically for the features we need which only VLT® can offer. The difference between 25 years ago and today is that processes now run right at their limit – but not beyond. And to achieve that we cannot do without the precision control we can get from VLT®s.

Flemming Husum, Plant Manager, Marselisborg Wastewater Treatment Plant

The result

The drives have allowed the plant to adapt to load variations with maximum flexibility. This, together with a much higher than normal use of online sensors and smart process control, has created a facility which, in 2016, produced 234% energy (134% more energy than it needed for cleaning the wastewater). The surplus was enough to cover all the energy needed for pumping wastewater to the facility, and for treating and distributing drinking water. The plant has become a power station and a biorefinery, the world's first energy-neutral water service company to decouple water from energy, and the first to create an energy-neutral catchment area for 200,000 people, covering the whole water cycle.

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electricity generation results in 30% annual net surplus, after internal consumption

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