From industrial age to green revolution
At Stockholm Royal Seaport, a new, sustainable neighborhood is being built on an industrial site. But first, the contaminated soil is being remediated with KLOZUR® persulfates so that future residents can live here in good health.
Viewed from above, the city of Stockholm seems to shimmer: Bright architecture, green parks, and a network of bridges are densely clustered around wide channels of the Baltic Sea.
These waterways have been integral over the years to Stockholm’s development into one of Europe’s leading cultural and commercial centers. Yet the geography is not without its drawbacks.
Lack of space is a major contributor to the current housing crunch in Sweden’s capital, a country where nearly 90% of the population lives in cities.
A role model for green urban development
That is why the City of Stockholm has undertaken a massive redevelopment of its historical Royal Seaport district.
The Stockholm Royal Seaport was once the site of a sprawling manufactured gas plant (MGP) and a main harbor for coal transport. Now, this area is poised to become an international role model for green urban living. When construction is complete in 2030, at least 12,000 new homes and 35,000 workplaces will be powered by renewable energy and connected by public transport and walking or cycling paths.
Circular waste management and an integrated commercial and residential concept aim to ensure self-sufficiency and a minimal environmental footprint. Designated space for urban gardening, an accessible shoreline, and repurposed industrial buildings will transform the Stockholm Royal Seaport from an abandoned remnant of the city’s coal age into an attractive and highly sustainable new neighborhood.
Starting with a clean foundation
But first there is work to be done. Once the main source of power for industrializing communities at the end of the 19th century, MGPs have left considerable organic and inorganic contaminants in the location where they operated. Over time, these residues release emissions through soil vapors that can pose a health threat to people living in the area. Thorough soil remediation must take place before any building can begin.
This is where persulfates come into play. Sodium and potassium persulfates are powerful oxidants — in other words, they rapidly degrade harmful compounds into nothing but benign basic components, like oxygen and carbon. The KLOZUR® SP-brand environmental grade sodium persulfate produced by Evonik Active Oxygens has been formulated to treat a wide range of contaminants, including the coal tar and naphthalene commonly left behind by MGPs.
“One common way to restore contaminated sites is simply to dig up the impacted soil and transport it away. But that just moves the problem somewhere else and causes traffic from heavy-load transport,” points out Josephine Molin, a Stockholm native and Technology Applications Manager for soil and groundwater remediation at Evonik Active Oxygens. “On-site treatment is a more responsible approach. Using products like KLOZUR® SP actually eliminates the contamination right in place — or ‘in situ,’ as we say in the industry.”
For the Stockholm Royal Seaport, the city decided on a method that combined soil stabilization with cement binders and contaminant destruction using persulfate. The less-permeable clay layer will be mixed with persulfates and binders to essentially seal away harmful substances through a combination of oxidation and immobilization. Meanwhile, the more permeable soil layers will be injected with persulfate solution in order to completely break down the harmful substances.
The full treatment with KLOZUR® SP is expected to be completed by 2024.
Ready for the future
Persulfates are not only effective at cleaning up the residues of the past; they also have a role to play in building a sustainable future.
For one thing, persulfates are produced through electrolysis, a process that requires a lot of electricity. The electricity for Evonik’s persulfate production is generated by hydroelectric power — an emission-free power source.
For another, persulfates enable in-situ remediation that allows for safe reuse of the site while keeping it fundamentally intact. There is no need to transport the contaminated soil away in heavy trucks, which prevents emissions and is less disruptive to the surrounding community.
“This kind of treatment harmonizes with the reduce-reuse-recycle approach of the whole Stockholm Royal Seaport project,” says Josephine Molin. “The plant was once a major source of power for the city and important for its development. Today, we have the knowledge to move beyond fossil fuel, but this site and its infrastructure will still contribute to powering a new, greener development.”
Molin smiles, “I rather like that the big old brick buildings of the Stockholm Royal Seaport are being repurposed into cultural centers. We are setting the stage for the future by building on the past.”