Removing PAH from lake sediment

A lake in central Sweden is situated next to an old industrial site used for treating railway sleepers and telegraph poles with creosote.

After industrial activity ceased several years ago, it was apparent that the soil was heavily polluted. Contaminants had also found their way into the lake and part of its tributary river.

The local environmental authorities therefore embarked upon a clean-up operation, beginning with a soil remediation phase of the industrial site itself, which is now complete.

The next stage is to treat the lake and riverbeds, which are contaminated with polycyclic aromatic hydrocarbons, also called PAHs, which are often found in creosote. These are harmful for the environment and human health, with some known to be carcinogenic.

The area to be treated is around 31 000 m² in size, containing an estimated 30 000 m³ of sediment.

The full-scale project got under way in the autumn of 2021 and is forecast to take around seven months, though stoppages are likely during the harshest winter weather.

The pilot test showed that our filter was able to reduce PAH by 99,3%, and we expect to replicate this throughout the project. As DESOTEC filters are mobile, they are easy to try out in situ, which provides more reliable results than lab tests and gives clients the confidence to go ahead with large-scale projects.

Based on the pilot test, our calculations show that it should not be necessary to exchange the filters, but we can do so if concentrations of PAH are unexpectedly high. Such flexibility is one of the key advantages of DESOTEC’s filters. The modular nature of our system also makes it simple to add or remove filters if necessary, without the client needing to make a major upfront investment.

DESOTEC also handles all waste, transporting spent carbon safely away from the site in closed filter units. It is taken to our facilities in Belgium, where it is analysed so that the right measures can be taken for handling it. All molecules that were adsorbed onto the carbon are desorbed inside DESOTEC’s reactivation furnaces and fully destroyed in line with national and European legislation by an incineration and neutralisation set-up. The entire installation and its emissions are continuously monitored online, guaranteeing that only harmless water vapour exits the chimneys.