About the project
PFAS REMOVAL IN DENMARK
For the RESC – Rescue & Safety Center in the municipality of Slagelse, the client wanted to find a solution for the removal of PFAS from the heavily PFAS-contaminated water streams originating from the fire training site. This includes surface runoff, process water from exercises, drainage water, as well as upper groundwater from the nearby meadow area.
To find a solution for this, ULTRAAQUA has conducted an extensive research project to investigate how to accomplish PFAS removal. This led to the implementation of a full-scale PFAS treatment plant, providing valuable insights and results on how to remove the so-called “forever chemicals”.
The project was actively ongoing from October 1st, 2022, and completed on December 1st, 2023.
WHAT THE CLIENT NEEDED
TREATMENT OF PFAS-CONTAMINATED WATER STREAMS
In 2019, the fire training site in Korsør was identified as a significant PFAS source, due to the high amounts of PFAS in the firefighting foam that has been used throughout many years. This includes both the site itself and the surrounding areas with meadows and allotment gardens, which are heavily contaminated with PFAS. RESC is a part of Slagelse Municipality, which has taken action to stop the spread of PFAS from the area.
As a result, in 2022, RESC and Slagelse Municipality tendered the establishment of a comprehensive solution to collect surface runoff during rainfall, firefighting water from exercises, draining water from the area, as well as upper groundwater from the nearby meadow area. The solution to clean these water streams was required to be below 3.5 ng/l for PFAS-4.
THE SOLUTION
FULL-SCALE PFAS REMOVAL SYSTEM
The complete system to be designed is required to handle the total amount of rainwater, firefighting water, and draining water from the RESC site, as well as the collected upper groundwater from the meadow.
This led to the construction and establishment of a robust and efficient solution that according to initial analysis results can reduce PFAS-22 from approximately 25.000 ng/l to below the detection limits for PFAS-22 (<0,3 ng/l).
A buffer solution for both the upper groundwater in the meadow and the rainwater from RESC’s areas ensures the collection of drain and rainwater. The cleaning processes are simple to operate and produces minimal waste. These processes contribute to ensuring stable and constant compliance with the municipality’s PFAS limits (PFAS-4: 3,5 ng/l).
The process steps of the treatment plant are as follows. The four buffer tanks at the RESC site have a total buffer volume of approximately 130 m³, capable of handling a 20-year rainfall event. The buffer tank for upper groundwater from the meadow area has a volume of about 18 m³ and draws water from approximately 200 m of drainage pipes in the meadow.
The treatment plant is fed from the buffer tanks based on a control algorithm that considers the weather forecast for precipitation over the next three days. This ensures the smooth and constant operation of the treatment plant. For example, if rainfall is forecasted, the buffer system is quickly drained to have capacity for the expected amount of rain. Conversely, if no rain is expected, the water amounts are stretched, ensuring operation also in dry weather. During longer dry periods where no upper groundwater is available from the meadow, the treatment plant will recirculate with a low flow of water internally.
From the buffer tanks, the water is pumped to the treatment plant, where it is first filtered and then treated with bubble fractionation (Ultraaqua has submitted a patent application for this solution in December 2023), which removes and collects the majority of the medium and long-chain PFAS compounds as concentrate. Afterward, the water undergoes sand filtration, followed by distribution to two parallel lines with series-connected carbon filters (GAC) and series-connected resin filters. The resin filters contain various types of resin, which can be regenerated. The collected PFAS can be eluted from the resin and collected as a concentrate for destruction.
Last but not least, ULTRAAQUA has developed a method in the in-house laboratory where vacuum-UV at normal ambient temperatures and pressures can break down PFAS into harmless fluoride. This method will be tested in Korsør as a batch process for the destruction of the collected PFAS concentrates.
