Closing a legacy lagoon system with defensible PFAS performance
A legacy textile manufacturing site in the southeastern United States produced coated textiles containing PFAS for water- and oil-repellency. Historical operations left approximately 100 million gallons of PFAS-impacted wastewater stored in a series of unlined on-site lagoons. With the site in decommissioning and remediation, the project team needed a practical path to treat lagoon water and discharge it to a nearby river while meeting a state-mandated threshold of below 70 parts per trillion (ppt) for PFOS and PFOA.
The work called for more than selecting a technology. It required a treatment strategy that could hold performance in the field, with clear verification through standardized PFAS testing and consistent operational control.
When water chemistry is complex, operations decides whether treatment holds
Lagoon water chemistry introduced immediate constraints. Total dissolved solids (TDS) and total suspended solids (TSS) were elevated, increasing the likelihood of fouling and limiting media life if solids management slipped. Biological activity in the lagoons added variability, influencing pretreatment needs and run stability. A remote site location tightened the margin for error on mobilization, startup and troubleshooting, especially when equipment adjustments required fast decisions.
Meeting an ultra-low discharge target under these conditions meant the solution had to protect the PFAS polishing step from upstream variability. The plan also needed an operating model that stayed tuned after commissioning, not just installed.
A treatment train built to protect ion exchange performance
Onterris worked alongside the client team to design and deploy a treatment train that prioritized pretreatment before PFAS removal. The system used GAC upstream to reduce co-contaminants that can compete for treatment capacity. A back-washable sand filter is used to remove suspended solids and stabilize influent quality before polishing.
With upstream variability controlled, the project applied single-use ion exchange (IX) resin as the primary PFAS removal technology. Ion exchange provided a strong affinity for PFAS at low concentrations while supporting a compact vessel footprint. Field teams then optimized flow and loading to maintain consistent treatment efficiency as lagoon conditions shifted. Verification relied on national standard PFAS testing protocols to confirm results and document defensible performance against the state discharge requirement.
PFAS treatment succeeds when the system runs like an operation, not a pilot. Tight commissioning, a clear sampling cadence and responsive remote support kept performance steady even as lagoon water conditions changed.
Results that supported discharge and a repeatable closure pathway
The treatment train achieved PFOS and PFOA levels below the state-mandated discharge limit of 70 ppt while treating approximately 100 million gallons of lagoon water. Pretreatment reduced operational pressure on the ion exchange step, supporting stable performance in high-solids water and predictable treatment outputs.
Work continues as part of the broader decommissioning effort, with the operating approach serving as a repeatable model for legacy industrial sites managing PFAS and other emerging contaminants. The project reinforces a practical takeaway for environmental managers and remediation leads: reliable outcomes come from pairing chemistry-driven design with disciplined commissioning, documented verification and sustained operational support.
