PFAS in the greenhouse at a research institute

The greenhouse experiments are being conducted to develop knowledge for a remediation location in Krimpen aan den IJssel. This is where we talk to Arthur van de Velde, who is a senior consultant on soil and soil remediation, and a co-owner of TTE Consultants, which was founded 26 years ago. During that time, it has often worked on complex soil remediation projects. Van der Velde was called in by the Ministry of Infrastructure and Water Management as the project team’s stakeholder manager for the cleaning up of the former site location in Krimpen aan den IJssel.

Remediation and redevelopment

Tom Bosma is a soil and water quality researcher and, before joining Deltares, he worked for Wageningen University and Research Centre, among others, as a student supervisor. His motivation is to develop knowledge that is good for the environment and nature, preferably in a role linking practice and science. He has worked on tackling all kinds of soil pollution since the 1980s, including projects in Switzerland. Currently, he is investigating the removal of PFAS in the soil remediation project in Krimpen aan den IJssel (Stormpolderdijk). The IMC (isolate, manage and control) method has been used here since the late 1980s. In October 2018, the Ministry of Infrastructure and Water Management signed a contract with Dura Vermeer to excavate the core of the contamination in order to make the site suitable again as a business park. During the preparations for the clean-up operation, a low concentration of PFAS was also found in the groundwater. It is leaching slowly out of the bottom ash present on the site. The PFAS aren’t a risk or obstacle for the safe use of the site as a business location. Nevertheless, groundwater will continue to be removed in the future for the purposes of site drainage. The secondary discharge from the bottom ash means that this water will be contaminated mildly with PFAS and it will have to be treated before being discharged to the surface water, because there are already PFAS in the Hollandse IJssel.

Controlling the conditions

Bosma: ‘PFAS have already been found at the EMK site in the extracted groundwater. And so the Ministry wants to look at whether we can tackle this with, for example, adsorbents, microbial degradation or other natural solutions such as vegetation, or possibly combined approaches. Researchers from institutes such as KWR, Wageningen University and Research Centre, Leiden University and Delft University of Technology are now working together on this challenge, each on the basis of their own area of expertise. That includes the experiment with sunflowers in the greenhouse on the campus. On the site itself, we are working with more plants such as willows, sunflowers, birch trees and reeds. We know these plants can absorb a lot of PFAS. But because you can’t control all the research parameters on a site of this kind, additional laboratory tests are required. We also want to start looking at things like how light affects breakdown processes. We are doing this with NanoSIMS and stable isotopes. It is convenient that our Delta lab is around the corner. They have already looked at the first harvest from the greenhouse.’

Van de Velde: ‘PFAS contamination can now be found throughout the Netherlands and our national policy is that, when we find it, for example in a remediation operation, we remove as much as is reasonably possible from the environment. The techniques currently at our disposal are too expensive to do this cost-effectively. We want to tackle this issue by studying combined methods. So the use of plants has also been included in our research on the EMK site. The clean-up of this old 5.5-hectare industrial site will cost a lot of money. But even then, we will have to carry on pumping up the groundwater that is contaminated with PFAS. A widely used approach is post-cleaning with activated carbon. If we also manage to remove some of the contamination with plants, that will reduce the costs and also be valuable for the environment’.

In the greenhouse

Bosma continues: ‘We are working with some flowers in the greenhouse at the moment because they grow quickly. They were planted in sections in combination with substances that can bond the PFAS. So there is a different combination in the substrate in each section but water is flowing everywhere below with a given amount of PFAS. The first question is whether the substrate helps the plants or not. The second question is how much PFAS the plants then absorb. Even now, we are already seeing PFAS being removed in our experiments in the greenhouse: the sunflowers are absorbing PFAS from the groundwater: more than 1000 times as much as in the tests on the EMK site.

What happens to the plants in the end?

Bosma: ‘We are also looking abroad for this, and in particular to the Swedish Agricultural University. They are conducting a similar experiment there with plants and combining them with other technologies. For example, they are looking at electrolysis as a way to break down PFAS. They use willows in a post-treatment process and harvest them to make pellets for a biomass power plant. In the next step, they look to see whether the PFAS in the pellets are incinerated completely: it’s not that easy to incinerate PFAS. Which is hardly surprising: that’s the very reason it’s used in firefighting foam. But it’s certainly another thing we want to investigate further for our situation.’ Van de Velde also still sees this as a challenge. ‘As in adsorbents, PFAS in plants eventually become concentrated and that continues to be the difficulty. What do you do with the plant residue in the end? It’s good to know that other people are already developing knowledge in this area and that we can draw on their work’.

Breaking down PFAS

Bosma: ‘We also looked at the PFAS in the water flowing in and out of the tanks on the EMK site. We saw that FOSAA was eliminated and that the level of PFOS (the most toxic PFAS) actually increased. That’s important to know but it’s obviously not the result you want. So we conducted additional research in the laboratory looking at how PFAS break down. The difficult thing is that the total level of breakdown is not clear at the moment, either for us or in international research. We are seeing the elimination of PFOS in particular in our tests, in association with an increase in smaller PFAS. It looks as though the PFOS gets cut up into smaller pieces. Fortunately, the smaller PFAS are less toxic than PFOS. So this is a positive result in that sense. In addition, we know that there are bacteria that can remove the fluorine. The ultimate aim of our research is to deliver a solution based on a combination of technologies that can remove and, ultimately, completely break down PFAS in soil and groundwater. By using plants as part of the solution, we can achieve our objectives for better living conditions and biodiversity in the urban environment.’

At Stormpolderdijk, the former EMK site, a range of partners are working together on PFAS removal. KWR and Deltares are investigating the use of various technologies and also looking around their own knowledge network for the right combinations. Dura Vermeer and TTE Consultants are contributing practical knowledge and working with the Ministry to identify the best possible application for possible upscaling. Van de Velde: ‘Collaboration between knowledge, practice and the national government often produces a good and workable solution. At least, that’s been my experience. The solutions aren’t left in a report on the shelf: they are actually applied in practice, where further development takes place. On the other hand, research also takes time. At present, we are already seeing effects (10% removal by plants) on a laboratory scale, but what does this mean in practice? Van de Velde: ‘I expect that a combination will be found in three years that works well for the PFAS groundwater at the site’.

The ultimate goal

Bosma: ‘When it comes to PFAS, I really hope we can reduce use to acceptable proportions. Where that can’t be done, for example in medication, we need to learn to use it better. I would like to contribute to the knowledge needed to achieve those goals. Because these substances don’t break down spontaneously, if at all, and they can harm health and the environment’.

Van de Velde: ‘Hopefully, the solution for the EMK site will also ultimately contribute to the improvement of PFAS removal at other Dutch sites because that is what we want to achieve. He concludes with ‘I’ve been working on soil remediation projects for about thirty years. When I started, the innovation at that time was research into the use of bacteria to break down contamination with VOCl (Volatile Organic Chlorine Compounds) and BTEX (Benzene, Toluene, Ethylbenzene, Xylenes). When we started on that work, there was a lot of criticism. The idea was that it wouldn’t be possible on that scale. These days, it’s standard practice. In short, it takes time. But if we are willing to invest in promising solutions, and to maintain that effort, we can solve our problems’.