Removing PFAS and contaminants from leachate

The Shoal Bay Waste Management Facility receives more than 180,000 tonnes of waste each year from 164,000 residents who live in the greater Darwin region (Northern Territory, Australia). Due to the region’s high rainfall, the facility also generates large volumes of leachate that must be treated and kept out of the surrounding environment, which includes ecologically important habitat.

Leachate is a complex, odorous and harmful liquid generated in landfills which is generated after rainwater or groundwater passes through waste materials that contain heavy metals, ammonia, and other substances created from putrefying waste.

PFAS are a synthetic group of chemicals that have been manufactured for use in a wide range of consumer and commercial products. As these products reach the end of their useful life, they are discarded, finding their way into landfills, becoming an issue for the operators of these facilities.

The WCG team designed and engineered a PFAS treatment solution after finding that there was nothing ‘off-the-shelf’ that was feasible for leachate. The result was the LEEF System®. This patented process has been installed as a key component of the leachate treatment plant, specifically to remove PFAS from the leachate.

The LEEF System® uses foam-fractionation to remove up to 100% of PFAS contaminants. Foam fractionation takes advantage of the way PFAS attach to air bubbles. By introducing controlled amounts of air into the system in a specific manner, the air bubbles rise to the top and then are skimmed off, and the highly concentrated PFAS contaminants are removed.

In full production the plant is processing up to 140,000 litres of leachate daily, with its capacity being readily scaled to meet higher demands or scaled down as needed. Other key benefits of the LEEF System at Shoal Bay:

• Remove up to 100 per cent of PFAS contaminants
• No chemical additives
• Operates with low energy consumption and minimal operational requirements
• Eliminates the need for costly pre-treatment such as filtration or coagulation (in contrast to more conventional methods like reverse osmosis or activated carbon)
• Continuous flow system
• Designed to be both scalable and modular, allowing for easy customisation

In addition to removing PFAS, the plant integrates biological and ecological treatment processes to remove the balance of contaminants. Treated effluent from the LEEF System® is further processed via a biological treatment plant which uses microbes for nutrient removal and a wetland treatment for a final polishing stage to remove residual nutrients and heavy metals.

Finally, the treated leachate is used to irrigate a Vetiver grass crop. This is a process of phytoremediation, whereby plants are used to clean up the remaining contaminates. The Vetiver also stabilises the banks of the capped landfill cells. Evapotranspiration results in a zero liquid discharge closed loop treatment solution.

Results indicate that regulatory requirements are being met and exceeded, with up to 100% of PFAS contaminants being removed.