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Copenhagen’s ‘blue transformation’

True integration of urban design and wastewater management achieved significant change.

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  • What we know
  • What we’re doing
  • What it’s worth

What we know

Swimming in Copenhagen’s harbour was unthinkable 15 years ago.

Close to 100 overflow channels fed wastewater into the harbour, making the water heavily polluted. The city addressed the problem by investing in the complete modernisation of the sewage system.

This ‘blue transformation’ involved modernising the sewage system, adopting a cleaning programme, diverting local rainwater, and commissioning a strong urban design to create a recreational space.

The solution was a true integration of urban design and wastewater management. It involved a collaboration between partners, including researchers, academics, architects, planners, engineers, municipal and private sector organisations, leading to the innovative solution of a harbour bath.

People sitting on dock front

What we’re doing

A combination of innovative solutions were used to achieve a clean harbour.

These included mechanical, biological, and chemical wastewater treatment to remove nutrients, salts and minimises the discharge of heavy metals.

Combined sewage reservoirs – reservoirs that store wastewater until there is capacity in the system – were used. A reimbursement scheme in which a landowner connected to the sewage system was reimbursed a connection fee if the rainwater is decoupled and discharged locally was implemented.

Further, 55 overflow channels were closed and an automatic warning system, that calculates the bacteria in the system and provides an online forecast on the cities website whether it is safe to swim, was introduced.

Copenhagen waterfront with colourful houses and boats
Copehagen harbour

What it’s worth

Water quality improved, and the city of Copenhagen was able to open the public harbour baths.

Today, the harbour is one of the trendiest spots in the city, and each summer and spring, the area is bustling with BBQ parties, couples strolling along the pier, and students, families, and businessmen having a swim in the heart of the Danish capital.

Knock-on effects include a 50-100% increase in real estate prices for flats in the harbour area, revitalisation of local businesses, and of course, improved water quality. Other benefits include more diverse flora and fauna returning to the area, reduced risk of urban flooding, increased recreational space, job creation, and increased liveability.