Water Washing

Constructed wetland filters greywater before it is infiltrated back into the soil.

  • Wastewater filters through the constructed wetland so plants can absorb the organic matter.
  • Up to 500 gallons can be filtered per day.

The primary method of greywater treatment occurs on the third floor terrace of the Bullitt Center. Here the interior floor plate has been pulled back for daylighting purposes, creating a perfect place for a high performance roof garden.

The garden is entirely of equisetum, commonly known as horsetail. These plants are extremely hardy and thrive well in Seattle, and are a natural choice for a wetland that is expected to work so hard.

Greywater from the taps and showers is pumped to the garden from a 500-gallon tank in the basement of the Bullitt Center. Once at the third floor terrace, it is dispersed through a series of drip lines into the aerated layers of gravel and soil. Here, the water can be evaporated and the plants can soak up the nutrients that would be harmful to a normal ecosystem.

The water is then collected at the bottom and pumped through several more times until the water is sufficiently clean, then it is pumped into the bio swales along the western edge of the site. Here, more organic matter can be absorbed by the plants before the clean water makes its way down the 20 foot deep gravel tubes which deposit the water into the aquifer.

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