PFOS Removal – Launceston
Treatment System Trial for Removal of PFCs from ARFF Dam at Launceston Airport – 2012
MDW Environmental Services (MDWES) were engaged by Air Services Australia. The Scope of Work was to undertake a Detailed Site Investigation (DSI) of a retention pond and trial hydrocarbon removal technologies. The works were part of Air Services Australia ongoing efforts to control contamination from airport activities and in particular fire fighting activities which can release fluorinated compounds (PFCs) into the environment. The trail took place at Launceston’s Aviation Rescue Fire Fighting (ARFF) compound. Runoff from Fire fighting at the compound is directed into an onsite retention pond and it was this pond that was the focus of the trail.
Historically fire fighting at the Launceston Airport has been through the use of Aqueous Film-Forming Foams (AFFFs) which are widely used both nationally and internationally. AFFFs contain proprietary mixtures PFCs which have typically contained Perfluorooctane Sulfonate (PFOS), Perfluorooctanoic Acid (PFOA) and Fluorotelomer sulfonate (FTS). Emerging research shows that PFOS, PFOA and to a lesser extent FTS are extremely persistent in the environment. Potential bioaccumulation and toxicity of these chemicals has led to scrutiny and some action by industry and regulators. For example, perfluorooctane sulfonate (PFOS) has been listed in the Stockholm Convention and industry has implemented some measures to restrict environmental discharges and replace existing products.
The DSI identified elevated PCFs in the ponds and that the retention pond was leaking and that there was a risk of pond embankment wall failure: potentially contaminating nearby agricultural land. An endangered species of frog (Growling Grass Frog) was also noted living in and around the pond, so any rectification works would potentially require maintenance of the water levels to mitigate risk to the endangered community.
The treatment system chosen for the trial was a Mycelx membrane, capable of capturing persistent, water soluble hydrocarbons. Due to potential for pegging with silt, two stages of sediment removal cartridges were utilised prior to the hydrocarbon-capturing filter cartridges. The presence of the Growling Grass Frog community posed an additional constraint with any method of drawing water from the pond needing to pose minimal risk to the frogs.
Samples were collected – prior and subsequent to each stage of treatment, to map PFC concentrations across the treatment cycle – on a daily basis for three days.
The results were consistent with expectations – the anticipated reduction of contaminant levels across the four stages of treatment were verified – however it was noted that due to much higher contaminant loadings (compared to other sites), not all contaminants were removed in the single pass.
Importantly, the specific role of each stage of the treatment process was made evident, and their crucial nature reinforced, by the analysis. Overall contaminant reduction was as follows:
- Removed more than 89% of PFOS
- Removed more than 92% of PFOA
- Removed FTS (6:2 FTS) to below detectable limits;
After trailing the process, the system was demobilised and retrofitted according to recommendations and a trial on the modified system undertaken. Analysis results confirm exceptional results, as follows:
- Removed more than 98.5% of PFOS
- Removed more than 95% of PFOA
- Removed FTS (6:2 FTS) to below detectable limits
The results indicated that the system is capable of removing most, if not all of the contaminants, but that a single pass would be insufficient to provide the surety a regulator would seek prior to approving discharge of treated water to the environment.
MDWES successfully project managed the Site providing solutions to a number of complex environmental issues. This in part was achieved through in large part via a strong collaborative partnership with Mycelx and good client relationship, developed by the professionalism of the MDWES Team.