King County Water Reuse

King County, 
Washington

King County Water Reuse

Project Highlights: 
  • Included a countywide reclaimed water feasibility study for new reclaimed water treatment and distribution scenarios for facilities located is the Metropolitan Seattle service area.
  • Included study, design, and construction assistance for improvements to the existing reclaimed water system.

King County’s South Treatment Plant operates a reclaimed water system supplying on average, 0.38 million gallons per day (mgd) of Class A reclaimed water to various plant and end uses during the irrigation season. The County plans to double the production of reclaimed water in the near future to meet off site demand increases. Carollo was selected to assess the South Plant reclaimed water system’s ability to meet the Water Reclamation and Reuse Standards, recommend process improvements to increase system reliability, assess the capacity of the existing reclaimed water treatment system and recommend improvements that may be required to meet increased offsite demand. The work effort included:

  • Standards Review: Prepared a summary of the pertinent existing and pending standards, indicating where improvements were needed to meet these standards.
  • Data Analysis: Evaluated historical data to determine the factors affecting the periodic coliform and turbidity spikes.
  • Bench Scale Testing: Performed bench scale filtration and disinfection tests to improve filtration and disinfection efficiency.
  • Full Scale Testing: Determined the capacity of the existing filters and disinfection system.
  • Condition Assessment: Visual review and ranking of each piece of equipment to determine future whether future maintenance and rehabilitation efforts would be needed.