Natural remediation on the Dow site
Between 1970 and 1989, Dow produced dioxane in Terneuzen; a colorless substance that dissolves completely in water. The plant has since been demolished, but the dioxane is still in the ground. Dow investigated ways to remediate this soil. We found a green way to do this. Literally!
240 poplars
Research indicates that dioxane breaks down rapidly under the influence of ultraviolet light and that trees can absorb dioxane. For this reason we planted 240 poplars on the site in Terneuzen in 2013. The trees absorb the dioxane-contaminated groundwater, the water flows through the tree and eventually ends up in the leaves. In daylight, the dioxane comes into contact with ultraviolet light there. This causes it to partially break down. Of course, some of the water also evaporates. That's fine, because this also causes the remaining part of the dioxane to evaporate. In the latter case, the dioxane breaks down in the air.
Good bacteria
Annually, we analyze the process by taking various measurements in the air, soil and water. This is how in the first year we found out that there was relatively little dioxane in the air coming from the leaves. This meant that some of the dioxane must have been broken down earlier in the process. And that was correct! Soil samples in fact showed that the bacteria on the roots were responsible for this. They break down much of it before it even gets into the leaves. In the coming period, we will extract bacteria from the roots and start cultivating them. We will eventually harness these to address the source of the pollution.
10 more years of patience
As for the future, Cees van Houwelingen, Operations Regulatory Services Leader at Dow, has the following to say: “The monitoring results show that the system is working well. I think we need another ten years or so for full remediation. And when the trees have completely cleaned up the contamination, we will have saved a lot of money in a natural way compared to the traditional remediation effort. A wonderful example of ecosystem services and an extra reason to be prudent with our natural capital. The effective impact of phyto-remediation has been demonstrated, but now nature just needs some more time to do its work. So we'll just have to be patient for a little while longer.”
