Per- and polyfluoroalkyl substances (PFAS) are a family of thousands of synthetic chemicals prized for their heat, water and grease resistance — and notorious for their persistence in the environment. For wastewater utilities, PFAS arrive through industrial discharges, landfill leachate, firefighting foam legacy sites, and everyday consumer products, then concentrate in effluent and biosolids.
Why wastewater plants are at the centre of the PFAS conversation
Conventional wastewater treatment does not destroy PFAS. It largely moves them — partitioning these compounds between the liquid effluent stream and the solids stream. That means every Ontario WWTP is, in effect, a PFAS transfer point between its industrial users, the receiving water body, and the agricultural land that receives biosolids. Regulators know this, and both the federal government and the MECP are moving toward enforceable limits.
Start with source control — it is always the cheapest kilogram
Before pricing a treatment plant, build a source-control program. Map your sewershed's industrial users: metal finishers, textile and coating operations, semiconductor and electronics manufacturers, landfills and airports are the usual suspects. A targeted sampling program at suspected sources — rather than only at the plant influent — typically reveals that a small number of dischargers account for the majority of the PFAS load. Pretreatment agreements and pollution-prevention plans can cut that load at a fraction of the cost of end-of-pipe treatment.
Treatment technologies that actually work
When treatment is required, three families of technology dominate. Granular activated carbon (GAC) is the workhorse: proven, robust, but with media replacement costs that escalate for shorter-chain PFAS. Ion exchange resins offer higher capacity and smaller footprints, particularly for short-chain compounds, at a higher resin cost. High-pressure membranes (nanofiltration and reverse osmosis) remove virtually all PFAS but produce a concentrated reject stream that still needs management — often the deciding factor at smaller plants.
Don't forget the biosolids question
For Ontario utilities land-applying biosolids under NASM plans, PFAS in solids may become the binding constraint before effluent limits do. Treatment plants are receivers, not sources, of PFAS — but every kilogram they remove from the water column concentrates into the solids stream, creating what is becoming a regulated waste stream with dwindling legal outlets. Land application faces impending restrictions, landfills increasingly refuse PFAS-laden material, and Maine's 2022 statewide ban on biosolids land application shows how quickly the ground can shift. Proactive utilities are already characterizing their biosolids, diversifying outlets, and evaluating destruction technologies such as supercritical water oxidation and thermal processing. Waiting for a regulatory number to appear before sampling your own product is a risk position, not a strategy.
A practical 12-month roadmap
Months 1–3: establish a baseline with influent, effluent and biosolids sampling using accredited laboratories and proper clean-sampling protocols. Months 4–6: complete an industrial source survey and targeted source sampling. Months 7–9: develop the pretreatment/source-control program and screen treatment options with a defensible cost curve. Months 10–12: pilot the shortlisted technology and build the regulatory engagement file. A senior P.Eng. who has walked this path with other utilities can compress this timeline substantially — and keep your sampling defensible if it is ever scrutinized.