All the hard work in the laboratory should not go to waste, so we strived to find a method for implementing it in the real world. We have specifically been working with PFAS in water. Most of the PFAS regulations focus on waterworks and water treatment plants.
The different water treatment facilities employ various methods for filtering PFAS, including surface-activated foam fractionation (SAFF), nanofiltration, and the ion exchange method, which has been observed at Silhorko. However, the issue is that none of these methods can degrade PFAS, necessitating its disposal through incineration, which requires temperatures exceeding 1000 °C and releases new PFAS into the environment. Read more about this issue on our Sustainability page.
First things first - What is the plan?
Our initial idea was to incorporate our genetically modified bacteria into the filtration process. While this approach appeared to be the most intuitive at first, it later revealed various challenges, including compliance with GMO laws. Consequently, we opted for an alternative approach to implement our work, which involved purifying the enzymes rather than introducing the bacteria to a filter. Read more on Human Practice.
The GMO law is strictly guarding over everything that regards changing an organism’s genomic and plasmid DNA. The law is made to protect human health regarding gene technologies and the conservation of animal and plant life. These organisms need to be handled within a certified class 1 lab, where these organisms won’t get out. Some different paragraphs need to be considered, such as paragraph 9 from the law regarding environment and gene technology.
“Genetically modified organisms may not be exposed to the environment without an approval from The Environment and Food Ministry.”1
We complied with GMO laws by deciding to use the extracted enzymes, instead of the genetically modified bacteria itself, as they are a byproduct of the bacteria that can be cultured in a lab. This allows us to stay within the laws regarding GMOs. If the bacteria were to be used, then it would require that we make the waterworks get a GMO certificate which would be problematic and expensive, and would make our implementation less accessible.
After further research, we saw that Silhorko, one of the water filtration companies in Denmark, had a filtration solution for PFAS, which included beads instead of the carbon filtration solution and was currently used to remove PFAS. We knew from the literature that enzymes could bind to resin beads, so we thought of implementing the enzymes of our bacteria to these beads, by which the PFAS could be degraded while having a water flow. This would result in a filter solution, which was favorable since it could be integrated into the waterworks by adding another kind of beads to their ion exchange PFAS filters.
Furthermore, we realized, after our discussion with former Silhorko employee Søren Duch Hennings, that incorporating our enzymes into the beads would pose significant challenges. This difficulty stemmed from the contact between our enzymes and the PFAS molecules. If both were attached to the beads, they might not come into contact. On the other hand, if we only integrated the enzymes into the beads, there would be a risk of the enzymes not degrading the PFAS quickly enough.
This led us to the final idea of a tank where PFAS could be collected. In this tank, we could accumulate PFAS from all the various filtration techniques that Søren mentioned. This approach was not only more versatile but also easier for us to implement, as it would be simpler to adjust external factors to optimize enzyme activity.
In the following table, some consideration regarding the two options, resin enzymes or enzymes in a container, is displayed. This helped us gain an insight into what idea to continue with.
Adding the enzymes to a container would be the most favorable for us, which is why we decided to go with this solution. This way, we could keep the enzymes isolated and follow the GMO laws.
Our main product - How is it made?
The simple package of our project would be the container along with some pipes which would be installed so that all kinds of PFAS filtration solutions could be attached. Of course, our enzymes, vitroZymes, would be a part of the package as well.
Looking at the filtration solution from Silhorko, we would have to ask ourselves whether to add the resin to the external container or simply rinse the PFAS out of the resin filter using a water/ethanol mix (60% ethanol) and thereby add it to an external container. The beads from Silhorko were not originally designed for regeneration, but they could potentially be rinsed from PFAS if a mixture of ethanol and water were used, as can be seen in the figure to the left. What option to pick would require testing of the two methods, to see which one removes the PFAS the best from the beads.
As shown in figure 1, we intend to integrate our enzymes alongside existing PFAS filters such as Silhorko’s ion exchange solution. The swirling mechanism would need testing, and we would also need to determine if the enzymes encounter the PFAS, making it possible for degradation which is our main goal!
A significant amount of testing would be required, but this approach holds promise as one of the best solutions for degrading PFAS more sustainably. It is a user-friendly option for waterworks to implement at their facilities. All that is required is a container with water movement for the enzymes to react, along with periodic purchases of our vitroZymes.
Fig. 1: How existing PFAS filters could be integrated with our enzymes.
The future of our device and limitations
The container containing our vitroZymes would require extensive testing before the solution could be deployed in the real world. Experiments would include assessing the enzyme kinetics, determining the ease of contact with our enzymes, and evaluating whether the beads would be toxic to our enzymes.
The byproducts of our vitroZymes’ degradation should be considered further. Implementation of our solution requires complete control of the byproduct to make the solution live up to the goals of sustainability that we want to achieve.
After our discussion with Emil from Teknologisk Institute, we learned that a potential byproduct of the enzymatic reaction could be Hydrofluoric Acid (HF). This is a highly toxic gas that can cause burns and tissue necrosis1. We are aware of this issue, and further investigation is required before implementing this idea, primarily to determine its interaction with the enzymes in the aqueous solution and the amount of HF it might produce.
The ultimate goal for our implementation is to create a more sustainable solution for water treatment plants dealing with the PFAS issue, facilitating the degradation of these persistent chemicals. One thing is certain: this product will become essential in the future. It's only a matter of time before PFAS contamination becomes more widespread in our water supplies due to PFAS continuously accumulating in nature, leading to the same challenges currently faced by Tune and Fanø waterworks.
Engineering
Marx, C., Trautmann, S., Halank, M., & Weise, M. (2005). Lethal intoxication with hydrofluoric acid. Crit Care, 9(Suppl 1), P407. https://doi.org/10.1186/cc3470
