The steps are similar in Seattle, although I think we filter less. I'm having a hard time finding a concise but also technical description of water treatment steps. We definitely do:

- Ozone disinfection, and removal

- Tolt river supply only: water conditioning by filtering through "granular media." (Cedar river supply is clear enough without this step.)

- UV disinfection

- pH adjustment to avoid corroding pipes

- Flouridation for public health

- Chlorination as a final step as water leaves the treatment plant, and also at some downstream facilities (like a networking repeater; just to maintain chlorine levels that would otherwise have fallen due to distance from the upstream chlorination site)

Tolt: http://www.seattle.gov/utilities/your-services/water/water-s...

Cedar: http://www.seattle.gov/utilities/your-services/water/water-s...