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201 S. Jackson St., Suite 505
Seattle, WA 98104-3855
Phone: 206-684-1280
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Puget Sound shoreline next to the West Point Treatment Plant, Seattle

Research

The 2009 research in this garden was conducted by University of Washington researchers to field test results of a 2008 greenhouse study. This research tested how these products work as a soil amendment and how they affect the growth of edible and ornamental plants in a landscape.

Research and monitoring programResearch shows it's safe to use reclaimed water on our local farms and nurseries.

The goal of the program is to use the best available science and applied research within the parameters of our budget to demonstrate the safe and appropriate use of reclaimed water and biosolids compost. Our results are used to:

What did we look at?

  • Plant health: Are the plants getting all their vitamins?
  • Plant growth rate and leaf size: How fast and big are the growing?
  • Presence of trace metals or pathogens: Is it safe to eat the food crops?
  • Soil pH and nutrient levels: Is this good for the earth?
  • Salinity: Will salt build up in the soil?

What did we find?

  • Plant health: The plot with the biosolids amended soil and reclaimed water irrigation grew the biggest and had a plentiful yield.
  • Plant growth rate and leaf size: Plants irrigated with reclaimed water showed better growth than plants irrigated with tap water.
  • The plants are safe to eat: Soil and plant metals were of similar levels in each plot; metals present existed in non-amended original soil. Pathogens weren't a concern for any of the plots. It is normal for all soils to contain some metals and bacteria.
  • Soil pH and nutrient levels: Soil pH was within normal levels. Slight nutrient value in reclaimed water and high nutrient value in biosolids amended soil.
  • Salinity: There was no problem with salt build-up when using reclaimed water.

The plants

Food crops analyzed:

Lettuce Strawberry Carrots

Lettuce

Strawberry

Carrot

Ornamental flowers analyzed:

Delphinium Sunflower Amaranth

Delphinium

Sunflower

Amaranth

Additional food crops were also planted and were on the menu at a community luncheon held in September 2009.

Of interest

Sign for WateReuse Symposium
Poster
 (PDF, 5MB) presented at WateReuse Symposium in September 2009.

Biosolids, Reclaimed Water, and Really Good Food: a recipe for public acceptance
Biosolids, Reclaimed Water, and Really Good Food: a recipe for public acceptance
 (PDF, 551 KB)

Research has been conducted by Dr. Soo-Hyung Kim (external link) and Dr. Sally Brown (external link), UW College of Forest Resources (external link).