Background/Objectives. Loss of a concentrated aqueous film-forming foam resulted in per- and polyfluoroalkyl substances (PFAS) impact to infrastructure and nearby surface water. The infrastructure included a domestic/industrial sewer system and a stormwater system which service numerous industrial facilities. The sewer and stormwater systems were subsequently isolated to prevent further impact to the environment.
The sewer and stormwater systems were washed out sequentially using water flushes, sodium hydroxide and a specially formulated alcohol-based biodegradable solvent.
Approximately 6 million liters (ML) of wastewater and 6 ML of stormwater were collected and contained in 20m3 capacity tanks (isotainers), including the waste from the washing the sewer/stormwater systems. The objective of the project was to treat collected water to a concentration of less than 0.25 μg/L Sum of PFAS (28 compounds) as measured by total oxidizable precursor (TOP) assay. The project is the first example of use of ozofractionation for PFAS and for performance of a remediation system to be validated using TOP assay.
Approach/Activities. The combination of high organic load and PFAS from the foam concentrate in the collected waters and waste created a complex treatment challenge. Each isotainer contained a differing spectrum of organics, inorganics and variable PFAS concentrations. Isotainers containing the wash water from cleaning the sewer and stormwater systems with the caustic and solvent were also treated. Two companies teamed up to design and install an innovative ozofractionation treatment process. Ozofractionation utilizes ozone to create a stream of bubbles that separate and concentrate PFAS in a foam fraction that is created at the top of a series of vessels and separated as a PFAS concentrate. The high surface area created by ozone micro-nano bubbles allowed effective removal of PFAS to the foam fraction. The ozone provided the oxidative capacity to break down the organic load of the sewage. The process also efficiently handled and separated suspended solids. The primary waste generated from the process is a highly concentrated aqueous PFAS stream. The system was designed for a treatment capacity of 5,000 L/hr, and, given the urgent nature of the application, a full-scale system, was designed, installed and commissioned in four weeks.
Results/Lessons Learned. The ozofractionation process demonstrated the ability to treat high PFAS concentrations up to 4,000 ug/L as well as much lower PFAS concentrations whilst also handling the high organic load and other co-contaminants of the mixture of raw domestic and industrial sewage. A reduction of greater than 99.9% as measured by sum of PFAS (28), TOP assay, was routinely achieved. The system reliably removed long-chain and short-chain PFAS down below 2 μg/L. To reach the final treatment objective, a membrane filtration system was installed to reduce concentrations reliably below 0.25 μg/L TOP assay.
Ian Ross, Senior Technical Director and Global, In Situ Remediation Technical Lead/Global PFAS Lead, Arcadis UK
Ian Ross, Ph.D., is a Senior Technical Director and Global, In Situ Remediation Technical Lead/Global PFAS Lead at Arcadis from Leeds, West Yorkshire, UK.
His focus for the last four years has been on solely on PFAS after initially working on options for perfluorooctane sulfonate (PFOS) management in 2005 after the Buncefield Fire in the UK. He has was part of the team authoring and reviewing the CONCAWE PFAS guidance document and has published several articles on PFAS analysis, site investigation and remediation, including a recent book chapter on PFASs management.
He has been focussed on the bioremediation of xenobiotics for over 26 years as a result of three applied industrially sponsored academic research projects. At Arcadis he has worked designing and implementing innovative chemical, physical and biological remediation technologies.
He has evaluated the fate and transport, biodegradation potential and treatment options for contaminants including hydrocarbons, chlorinated solvents, nitroaromatics, PFAS, lindane (hexachlorocyclohexane), polychlorinated biphneyls (PCBs), Aldrin, Dieldrin and dichlorodiphenyltrichloroethane (DDT).
He has experience with multiple physical, chemical and biological treatment technologies and has won several national and international remediation awards for designing their application.