Winston wastewater plant reports month‑long nitrification failure after unknown QAC contamination; plant has recovered to meet permit

Chris, a wastewater operator for the Winston treatment facility, told council that an unknown, high‑concentration quaternary ammonium compound (QAC) entered the plant late in May and bonded with sludge, preventing nitrifying bacteria from surviving and causing a prolonged nitrification failure.

“We had some sort of cleaning agent or sanitizer that had come through,” Chris said, describing lab results that identified a cationic sanitizer compound. He said the plant considered chemical oxidizers and other remedies but delayed dosing while the system showed signs of natural recovery. He reported that, on the day of the meeting, the plant was “fully meeting the permit.”

Chris said staff located a lab in Virginia to run specialized testing, overnighted treatment materials to the plant and, after 31 days, observed signs of recovery. He emphasized that the exact source remains unknown; flow and dissolved‑oxygen data suggested the contaminant may have entered from the Green side of the watershed, but there was no definitive origin.

DEQ (the Oregon Department of Environmental Quality) was kept in contact during the event, Chris said; the department files routine reports and will determine whether enforcement action is warranted, sometimes months after an incident is reported. Council members were told that the plant now has better monitoring equipment to detect and trace future short‑duration discharges.

What happens next: staff will continue monitoring permit parameters, pursue upstream testing if the contaminant recurs, and coordinate with DEQ on any follow‑up testing or enforcement.