According to Paul Kloet, Deputy Director at Iv-Water, the project in Sluiskil correlates well with Iv-Water’s knowledge and experience. “These are the most interesting assignments for us. We can apply our knowledge to a practical issue that is linked to a current theme, which would be difficult to investigate on our own initiative. These are wonderful opportunities to examine how we can connect the entire chain more optimally.”

The latter is a greater goal within the division: to optimise the circularity of water. This begins with guaranteeing the quality of wastewater flows before they enter the natural environment, the intake of water for preparing drinking water, and stimulating the reuse of water flows in the industry. 

This project in Sluiskil, Zeeuws-Vlaanderen, is such an opportunity. Process Technologist Bart van der Veer is leading the research at HEROS on behalf of Iv-Water. The company processes Bottom Ash (BA) from various Waste-to-Energy Plants (WtE) into a building material using various techniques, including a washing installation. The core question is whether and how the washing water can be filtered or purified from PFAS? Of course, this can be done using modern purification methods such as reverse osmosis or ozone technology. But even more desirable would be to prevent high concentrations of PFAS from entering the wastewater in the first place.

Iv-Water is currently in the beginning phases of this research. “The licensing authority ultimately determines what is and is not permitted with regard to the discharging of PFAS,” explains Bart. “They warn of PFAS ending up in water flows, also through, for example, rainwater. For HEROS, however, the quality of the incoming waste-generated bottom ash varies greatly. The bottom ash is mostly relatively clean, but sometimes it still contains many unburned pieces: a potential source of PFAS. This unburned matter is sorted and sent back to the Waste-to-Energy Plant to be incinerated.”

However, this is not always sufficient. PFAS is artificial and has the property that it cannot be broken down by natural processes. It is a collection of chemical substances containing valuable properties for the industry sectors. It repels water, grease and dirt, which is why it is often and readily used in the clothing industry, the cosmetic world, but also, for example, in the production of lubricants or food packaging.

In addition, PFAS is very fine: the chemical substances cannot be entirely removed with standard purification installations and filters. In fact, says Bart: “Some substances do not contain PFAS, but sometimes this occurs following water purification, which is extraordinarily complicated.” There is no uniform solution, but what HEROS does as much as possible - returning the unburned matter from the waste-generated bottom ash - is one of the options that prevents PFAS from ending up in the environment. This is already the case in the Western Scheldt (Westerschelde), derived from various companies. Bart: “The licensing authority is clear on this: if a waste stream contains PFAS, as a waste processor you should only accept it if you have the appropriate installation.” Combined, there are many significant challenges and issues that make it difficult to determine what does or doesn’t work and the cost thereof. “PFAS consists of a range of substances, but there are also many technologies that can help. For example, an activated carbon filter is a good option,” says Bart. PFAS, for instance, loves carbon and attaches itself to it. A proven system but very expensive. “The question is whether this is necessary and financially feasible for a waste processing company.”

Then there is ozone technology. The substance ozone, composed of three oxygen atoms (O3), reacts with PFAS and breaks the chemicals down into, among others, CO2 and water (H2O). Moreover, ozone is a solution that leaves no traces in the water following the process. When ozone stops reacting with a substance, it rapidly reduces to oxygen (O2) gas. This technique is often used by drinking water companies. There are also several separation methods with which PFAS can be separated from other non-harmful substances and thus filtered.

Bart and his team will explore the already mentioned techniques and others in the coming months. Paul Kloet is curious about the results and hopes Iv-Water will gain substantial knowledge from this research. Paul’s goal is to retain the purity in the entire water chain and to intervene as early as possible in the chain to achieve the desired results. “As pure and reusable as possible, that’s what we strive to achieve. However, it cannot be avoided that when you conduct a lot of testing and have a lot of knowledge, you will inevitably come across harmful substances that need acting upon. But if you think circularly and reduce the chain - for example, at an industrial plant - you can control the quality efficiently because harmful substances are isolated more quickly.”

The HEROS project is, therefore, crucial for establishing an overview of the origin of PFAS. Bart: “We analyse where these substances originate and where in the process PFAS is entering a certain water flow. This is how we tackle the source in an ‘end of pipe’ situation. The source is sometimes much further back in the chain, namely in industry. We also examine specific places where PFAS ends up in wastewater. At HEROS, we have gained greater insight into which flows it enters and where it ends up in wastewater. Sometimes purifying a specific, much smaller side stream is more efficient. We are helping to gain insight in this, and in doing so, we examine which approach is feasible and preferable.”

Bart hopes and thinks he can do something for the world with this assignment in Sluiskil. “The fact that I can work with clean water and leave it clean is very satisfying. And especially because it can be solved with technology. We can now take on this role to find out.”