Wastewater Treatment

Collection Sewers• Collect wastewater and bring it to the

wastewater treatment plant– Combined sewer overflows: Take untreated

sewage and storm water to rivers, lakes and Puget sound during heavy rain events

Preliminary Treatment

– Bar Screen: located at the beginning of the wastewater treatment plant to remove large debris

– Influent pumps: transport incoming waste to the treatment plant

Primary Treatment

– Sedimentation Tank: Remove solids that are heavy and sink to the bottom as well as oil and grease that floats to the surface. • Primary sludge goes through solids treatment process

and liquids do through a different process

Secondary Wastewater Treatment– Aeration tank: Wastewater from the settling tanks flows

into the aeration tank, where microorganisms such as bacteria and protozoa eat material and nutrients, turning organic materials into solids

– Clarifying tank: Solid matter settle and are pumped to solids treatment process or recycled back to aeration tank.

Final Treatment

– Chlorination and contact tank: kill bateria and viruses

– Dechlorination: Remove toxic chlorine from effluent

Water Released to Puget Sound

– Effluent Pump: Transports effluent out to the environment