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Case

Water management

Industrial water treatment

Denmark’s first high-rise waterworks with softening system

19. November 2024

Solution provider

Frederiksberg Forsyning

Frederiksberg Forsyning is the local utility company in Frederiksberg.

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Challenge

Frederiksberg’s aging waterworks, built in 1999, faced the need for modernization to better meet residents’ needs and environmental standards. One primary demand was to soften Frederiksberg’s exceptionally hard water, which causes scaling issues for residents and businesses. However, given Frederiksberg’s dense urban setting and limited space, expanding horizontally was not an option. To address these challenges, Frederiksberg Forsyning reimagined the waterworks in a vertical format, creating Denmark’s first high-rise waterworks to optimize water softening within a compact footprint.

Solution

In November 2022, Frederiksberg unveiled its new four-story high-rise waterworks, a modern and space-efficient facility capable of softening 5.4 million cubic meters of water annually. Through this softening process, water hardness is reduced from 30 °dH (degrees of German hardness) to 10 °dH, resulting in medium-hard water. This carefully calibrated hardness level was selected to minimize corrosion risks in water pipes and installations, which can occur when water is softened below 8 °dH.

The water softening process uses a pellet method: calcium is removed by precipitating it on sand granules using sodium hydroxide (NaOH), which crystallizes calcium around the sand, forming small pellets that settle and are removed. As this process raises the water’s pH level, CO₂ is subsequently added to restore pH balance to neutral.

In addition to its softening capabilities, the high-rise waterworks includes advanced treatment technologies such as activated carbon filters and UV treatment to ensure water quality. The facility also integrates heat pumps, which capture thermal energy from drinking water, cooling the water while transferring the extracted heat to Frederiksberg’s district heating system. This innovative approach contributes 3% of Frederiksberg’s district heating supply, providing a sustainable energy source that would otherwise go unused.

Result

The new high-rise waterworks represents a major leap in resource efficiency and sustainable urban infrastructure:

  • Economic and Environmental Savings: By delivering softened water, the facility reduces the need for chemical descaling agents and detergents, saving residents time, money, and energy while decreasing chemical discharge into the environment.
  • Enhanced District Heating Supply: Heat pumps attached to the waterworks reduce reliance on external energy sources, reinforcing the local district heating network with renewable energy.
  • Knowledge Sharing and Engagement: As Denmark’s first high-rise waterworks, the facility attracts numerous visitors from both the utility sector and educational institutions, locally and internationally, eager to learn from its design and operations.