Maximised dredged mixture concentration

At Oskarshamn, South East Sweden, the harbour basin had been badly contaminated by a nearby battery factory. As the industrial activity had included the discharge of contaminated waste water over decades, the entire harbour basin – covering some 500.000 m² – was involved. The contamination included PCBs, dioxin and heavy metals, which slowly spread to the surroundings due to passing traffic.

The city council awarded the job to remediate the Oskarshamn harbour to Envisan, a company specialized in environmental remediation. Envisan constructed a complete treatment facility on site for treating the contaminated dredged sediments. A filter press was used to dewater the dredged sediments: The dry material was ultimately transported to a landfill nearby, and the process water was treated before discharge.

Some 400.000 m³ of contaminated sediments were dredged using a hopper dredger. The dredger passed the area slowly creating minimal turbulence. The hopper hold of the dredger was emptied by means of the DOP200. The submersible dredge pump was lowered into the hopper, where it pumped a mixture of the highest possible concentration to the dewatering plant.

As such, the DOP200 was a small cog in the entire remediation plant set-up.