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.
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The water treatment process can be described in five primary steps:
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.
The water travels through Sedimentation Basins where the heavier material settles.
Coagulation and flocculation remove turbidity as well as metals, including arsenic.
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
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.
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 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.