Steff Van Cauwenberg and Jochem Bloemendaal work at DEME. The environmental branch of this company – which was originally based in dredging – is providing both the knowledge and the soil treatment facility to remove PFAS from the soil at Schiphol.
What are your roles within DEME?
Jochem: I am a soil and environment consultant and mainly involved with the Dutch market. The standards, rules and protocols are slightly different in every country. The soil remediation sector is primarily driven by legislation and standards.
Steff: And I am company manager for soil remediation and treatment in the Netherlands. Not just for Schiphol, mind you, we do other environmental projects in the Netherlands with DEME. In this position I've been involved with Schiphol since last September. The facility purchase order from Schiphol arrived on my first day at work in the Netherlands. I could get started right away.
How did the company end up cleaning PFAS?
Jochem: The processing of dredged material and soil is strictly regulated by environmental legislation. DEME has traditionally had an environmental branch that focuses on dredged material processing. Soil remediation and treatment came later. Our research and development department is at the forefront of the soil treatment sector. We were already working on how to clean PFAS-containing soil before the knowledge of and regulations around PFAS emerged in Europe. We were already cleaning soil from Germany in 2015. In the meantime, we have cleaned more than 400,000 tonnes of PFAS-containing soil.
Steff: It helps that DEME is such a large and innovative organisation. You have much more scope and opportunity to tackle complex challenges in a progressive way. You see that there is a lot of experimentation in the market with different techniques. But you often have to deal with small-scale tests in controlled conditions. Important questions still have to be answered afterwards. Questions like: does it also work with large batches? What kind of residual products do you get? Is it cost-efficient?
Jochem: Thinking about that in time improves your process. We now benefit from the advantage in terms of knowledge and experience.
Did you have to modify the soil treatment facility in order to clean the Schiphol soil?
Steff: We didn't have to fundamentally adjust our cleaning method for PFAS. However, we did have to take a few additional and supplementary airport-related safety requirements into account.
The most important parts of our process are separating the fine fraction (sludge) and the coarser fractions (sand) in combination with ‘washing’ the soil. For the most part, what you do is move the contamination to the washing water. We then purify the PFAS contamination from this water. We do this using active carbon filters to which the PFAS ‘stick’. Our process broadly looks like this:
How do you know for sure that the facility is working properly?
Steff: It's not like: 'oh the installation has been set up so it will work now'. We continue to test all soil that comes out of the soil treatment facility against the reuse standards for soil. We monitor things continuously.
Together with people from Schiphol, we checked all parts of the facility for technical requirements and safety. Even though we built the installation, our own experts and Schiphol's experts check it. You want to be sure, right?
And what about sustainability?
Jochem: There are several components to sustainability. For example, the washing water is not discharged, but continuously recirculated and – after purification – reused. There are also water basins in which rainwater from the site is stored. This water is also used for the soil treatment facility. That saves on water consumption. The basins are designed for so-called ‘T100 showers’ that occur on average only once every 100 years. So, even during exceptional showers, all the rainwater can be collected. This kind of basin is actually a gigantic rain barrel.
Steff: Now suppose you were to dispose of all contaminated soil and dump it. That's not sustainable. We sometimes forget that soil is a primary resource. It's everywhere, but clean and reusable soil is expensive. With this project we clean the soil on site for reuse - that also saves a lot of transport movements.
Do you think the debate around PFAS has changed in recent years?
Jochem: Fortunately, I have recently seen an increasing distinction being made between PFAS producers and users, such as Schiphol. It makes a significant difference whether you add PFAS to the environment or whether you 'reallot' existing contamination by moving soil.
Steff: That's right. I expect that producers will soon be subject to increasingly strict regulations. So that emissions will be reduced or even disappear. We've all woken up. That doesn't mean we will never have to deal with substances whose harmful properties emerge later. Unfortunately, that sometimes takes a while. That was also the case with asbestos, for example.
What have you learned at Schiphol that you can use in other projects?
Jochem: That every person sees a situation from a different perspective. That can cause some friction.
Steff: That's why I find the residents evenings so valuable. Without the media in between, you are in direct conversation with the people who have concerns. I can then answer their questions directly. That's great.
Jochem: When I heard about Schiphol's plans to clean the ground 'themselves', I thought it was a noble ambition. They could also have said they would simply remove it. That would have saved a lot of hassle. It's brave to initiate an operation yourself, start research and go all out for reuse. If you live nearby, I can understand that you want to know what is happening on your doorstep. If there's one thing I've learned, it is to understand the importance of environmental communication. It is important to keep people well informed.