In search of a sustainable alternative to dumping at sea or disposal on land, a Scandinavian consortium blended contaminated sediment with a special mix of binders to produce a safe construction material for use in ports and harbours.
Stricter regulations have reduced the use of hazardous chemicals and heavy metals in industrial activities, but their legacy lives on in the environment, notably in polluted soils and sediments. One sector where they present a particular headache is in the shipping and port industry, where dredging routinely turns up sediment contaminated with the likes of carcinogenic PCBs, TBT, cadmium, lead and mercury. Port owners are caught between constraints on dumping sediment at sea, the cheap but polluting option, and removing it to be treated for landfill, an expensive alternative.
Enter a recent EUREKA project, STABCON, in which a Swedish-Norwegian consortium — of research bodies, binder manufacturers, port authorities and design consultants — sought to adapt the ‘stabilisation and solidification’ method to treat polluted sediments and other dredged material commonly found in Scandinavia.
Having worked together on an earlier study into the potential of the stabilisation and solidification technique in Sweden for the country’s environment protection agency, the project participants teamed up to test the method in a pilot study and draw up guidelines for ports.
A cost-effective solution
Led by Merox, a subsidiary of Swedish steelmaker Svenskt Stål AB (SSAB), they first compared the three alternatives for handling sediments — dumping, solidification and stabilisation, and dredging and disposing on land — from a sustainability perspective. Stabilisation and solidification proved to be a sustainable and cost-effective solution. Contaminated sediments are mixed, on site, with products that bind it to create a solid material that contains the hazardous substances.
As well as being more environmentally friendly than dumping and cheaper than landfilling, “this method offers a number of additional benefits,” explained Göran Holm, R&D director of the Swedish Geotechnical Institute, one of the project partners. “It reduces the demand for natural resources, such as blasted rock; and by treating the sediments in situ and using them in port areas, the need for transport is reduced, along with the health risks.”