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Tertiary Filtration Facility 

OLWS wants to keep you updated on active projects in our community. OLWS’ wastewater treatment facility needs a significant upgrade to comply with new Oregon Department of Environmental Quality (DEQ) standards for discharge in the Willamette River. This requires building a third level of treatment called a Tertiary Filtration Facility at the existing OLWS Wastewater Treatment Plant. 

You have the opportunity to see the inside of the Tertiary Filtration Facility and taking a virtual tour, click here. If you would like to take an in-person tour of the OLWS Wastewater Treatment Plant please email

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Photo of the Tertiary Filtration Facility

The OLWS wastewater system protects public health by collecting, treating, and cleaning approximately 1.5 billion gallons of wastewater a year through a two-step process aligned with current state regulations. OLWS’ Wastewater Treatment Plant operates 24 hours a day, 7 days a week treating the community’s wastewater before returning it to the Willamette River. The plant collects and treats approximately 900 dry tons of raw wastewater solids annually (called ‘biosolids’) that are transported and used to fertlize agricultural farmland. Wastewater treatment facilities play a key role in mitgating the spread of disease and in promomoting healthy waterways.

Construction is slated to begin in the next five years. This will supplement the existing two-step filtration treatment process (which met previous state standards). If these upgrades are not made, OLWS will be out of compliance with current DEQ standards and fined until compliance is achieved. Grants and loans, in addition to customer rates, will fund this vital infrastructure investment.

How Will OLWS’ Tertiary Filtration Facility Work? 

The facility will be built adjacent to existing infrastructure on OLWS-owned property at the wastewater treatment plant.

This involves screening larger debris and grit via sedimentation. Wastewater is held in a large sedimentation tank to remove solids that settle. Heavier solids sink, leaving lighter solids at the top. Once settled, the water at the top is sent for secondary treatment.

Soluble organic solids that escaped primary treatment are removed. This secondary stage also addresses smaller solids using tools that may include filter beds, bioreactors, and aeration ponds.

In the final stage, the treated wastewater is run through additional filtration and is disinfected to the highest standard via ultraviolet light (UV). Then, it’s discharged into the Willamette River

Water cycle

 If you would like a printed version of this information email please email


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