Water treatment process

A few miles upstream from the McKenzie River's confluence with the Willamette River, water is drawn and pumped to EWEB's Hayden Bridge Water Treatment Plant.

Diagram of EWEB water filtration process

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Five primary steps

The water treatment process can be described in five primary steps:

  • Disinfection
    Chlorine is added to the water for disinfection.
  • Coagulation and flocculation
    Alum is added in proportion to the river turbidity to form floc particles created from the suspended materials in the water.
  • Sedimentation
    The water travels through Sedimentation Basins where the heavier material settles. Coagulation and flocculation remove turbidity as well as metals, including arsenic.
  • Filtration
    Following sedimentation, the water travels through an extensive filtration process that removes sediment and other suspended materials.
  • Corrosion control
    At the end of the treatment process, pH is adjusted with caustic soda (NaOH) to reduce corrosion in plumbing systems.

The final product is crystal-clear and safe drinking water.

Once treated, water is transported from the treatment plant in large underground pipes to Eugene, where it is distributed to nearly 200,000 customers. Only enough chlorine remains to meet state and federal requirements to keep water safe as it travels through pipes to your tap.

The distribution system includes 28 reservoirs, 34 pumps stations and more than 800 miles of piping.

Glossary of terms
  • Flocculation
    The process by why which fine particles are caused to clump together into "floc." The floc can then settle to the bottom and be filtered from the water.
  • Turbidity
    Turbidity is a measure of the cloudiness of the water. The typical cause of turbidity is tiny particles of sediment in the water. Turbidity alone has no health effects. However, turbidity can interfere with disinfection. EWEBs filtration process effectively removes turbidity.

Email our water quality experts with questions or for more information, or call (541) 341-8500 ext. 2.