PORT ANGELES — The city of Port Angeles has clarified Monday’s wastewater bypass incident at its wastewater treatment plant due to storm surge from the recent heavy rainfall.
The spill prompted a 48-hour no-contact advisory from Clallam County Health and Human Services for the water in the harbor, which ended Thursday night.
This bypass is different from a combined sewer overflow in which stormwater drainage through the sewer system overloads and bypasses the treatment system completely.
During Monday’s wastewater bypass, the plant released about 3,300 gallons of partially treated wastewater though its main outflow, according to a news release from the city. That is approximately the same amount of water that is contained in the spa pool at Shore Aquatic Center, according to Ryan Amiot, the center’s director.
The water had been processed through the primary treatment process, but it did not go through the secondary treatment stage, the city said.
Primary treatment involves clarification in which heavier-than-water solids settle out and and floating solids and oils are skimmed off.
After primary treatment, the wastewater contains dissolved organic matter, fine suspended solids and pathogens.
The wastewater then receives biological treatment and disinfection during the secondary treatment stage.
The plant’s supervisory control and data acquisition system noted that the bypass began at 11:42 a.m. to 11:44 a.m.
During that time, one of the treatment processes within the plant was overloaded due to a rapid change in inflows that the pumps did not react fast enough to resolve.
That allowed the partially treated wastewater to bypass the secondary stage and exit the plant’s main outfall, which discharges about 1 mile offshore east of Port Angeles Harbor.
The plant’s pumping level control sensors have been adjusted and the plant has returned to normal operations, the city said.
