Impact analysis: cost-effective removal of PFASs
Waste water and leachate from rubbish dumps can be a source of new contaminants such as PFASs or microplastics. PFASs is a collective term for harmful substances used in the production of things like Teflon, water-repellent clothing and fire-extinguishing foams. The national government has established standards to keep these harmful substances out of our environment as much as possible. As a result, PFASs are often a problem when it comes to the testing of discharges. Additional efforts need to be employed to remove the PFASs from waste water and meet established standards.
Various techniques are available for achieving this, such as activated carbon and ion exchangers. The composition of the waste water and the concentration of PFASs will determine which techniques are suitable. As well as these considerations, cost, removal percentage and environmental efficiency also play an important role. To be able to weigh all these factors up, Witteveen+Bos has developed a method for assessing cost effectiveness based on Best Available Techniques methods: namely, the impact analysis tool, or ‘impact test’.
Impact analysis reveals effectiveness of purification techniques
An impact analysis involves simulating the discharge of waste water containing PFASs into a canal, sewage treatment plant or large body of saline surface water. In each scenario, a quantity of water with a concentration level of PFASs comparable to current real-world situations is used. The purification efficiency and investment and operational costs of commonly used techniques are then analysed in each case.
To test this model in a real-world situation, we conducted a case study at a representative rubbish dump in the Netherlands. The study showed that no good cost-effective solutions exist for discharging purified water into larger bodies of saline surface water. In order to meet the discharge standards, the purification efficiency of current techniques is still too low and the costs are still too high. The consequence is reduced water quality and an absence of cost-effective removal with sufficient environmental efficiency. To satisfy the requirements of the discharge test, extra measures are required.
Clear insight into costs of removing PFASs
New purification techniques for removing PFASs from water are being developed rapidly. Costs, removal efficiency, and compliance with discharge standards and other permit requirements are all crucial. The impact analysis maps these out quickly and accurately. Thanks to the case studies, this insight is already available for current techniques. But this knowledge also enables us to quickly and effectively assess new methods and provide advice on which technique for removing PFASs is best suited to a given situation.