Economic and environmental benefits of centralisation

The water utility in Mariagerfjord in Northwestern Denmark wanted to improve both economic and environmental benefits of its
wastewater treatment and decided to build a new state-of-the-art treatment plant.

The new plant will initially handle 75,000 PE but is constructed for 110,000 PE to accommodate the expected population growth over the next 25 years. The new plant is replacing 10 smaller plants, which have treated a total of 5-6 million m3 of wastewater annually. A 2,000 m3 digestion tank reduces the amount of sludge and has made biogas production possible. The new WWTP complies with the stricter requirements for discharging into a fjord, even though the cleaned wastewater is actually led nearly 4 km out into the sea. In fact, discharge of organic materials, nitrogen, and phosphorus from the new plant is significantly lower than the total discharge of all the 10 old WWTPs. As the new plant is placed 27 metres above sea level, the cleaned wastewater is discharged primarily by gravity through a pressure gravitational network. Finally, a two-string pipeline with separated sewers has been constructed to avoid the costly and unnecessary treatment of rainwater, which made up more than 50% of the total volume of sewerage water sent to the old plants.

Primary contact
Michael Ramlau-Hansen

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