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1 -- Wastewater enters
through a step screen system, where the paper and plastics are removed and taken
to landfills.
2 -- The influent then moves through a grit removal process, which
removes the heaviest particles and sand that are carried with the sewage.
3 -- Primary clarifiers are the next step; these are large tanks where
solids sink to the bottom to be collected by mechanical scrapers while floatable
waste is skimmed off the top. Before secondary treatment, wastewater moved from
the primary clarifiers to chlorine contact chambers, and then directly into
Puget Sound.
4 -- From primary clarifiers, wastewater is moved to intermediary tanks
where large plastic cylinders (Rotating Biological Contactors, RBC's) are
rotated through it. These cylinders are covered with bacteria that literally eat
much of the pollutants and oxygen-demanding components wastewater contains.
5 -- Following exposure to the "pollution-eating" bacteria,
wastewater enters secondary clarifiers where additional solids are settled out.
6 -- Wastewater then passes to the chlorine mixing and contact chambers,
where sodium hypochlorite is introduced to disinfect the effluent.
7 -- Processed effluent is then released 2000 feed off-shore and 230 feet
beneath the surface of Puget Sound. |
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