Net Zero Case Study: Bullitt Center — Water

February 21, 2015

Bullitt Center in Seattle

The Bullitt Center in Seattle, Washington, is one of the most self-sufficient buildings on the planet. It is net zero energy and, after the water reuse system is approved by city authorities, net zero water. Net zero means that the building uses the same amount as it creates or generates – it is self-sufficient. In a series of posts here on GBE, we will look at what makes this building tick.

Rainwater Catchment System

Rainwater falling on the PV panel roof of the Bullitt Center flows through the panels and into a 56,000 gallon cistern, which is actually a room in the basement. The system supplies non-potable water for all of the toilets, hose spigots, and the irrigation system.

A treatment system to take rainwater to potable standards is provided in the building, but it has not been approved for use by the City yet. The system will send the rainwater through a series of filters, including an ultrafilter so fine it removes viruses, and an ultraviolet disinfection system. Until the treatment system is approved for use, the building gets its potable water from the city water system.

Composting Toilets and More

Foam flush toilets that use less than a cup of rainwater per flush are used in all bathrooms in the Center. A natural soap helps the waste slide to the basement, where the waste is stored in one of several composting units. Wood chips are added to the waste, and with the help of heated air circulated through the units, about 90 gallons of compost are produced per unit per year. Temperatures in the composters are kept at 135 to 165 F to ensure that pathogens and contaminants are eliminated.

The compost and a nutrient-rich leachate that is drained from the units is shipped to a nearby composting facility and will be combined with other materials to be used as a soil amendment.

Gray water, waste from the sinks and showers in the building, is distributed to a constructed wetland on the second floor roof, where the water is filtered by the soil and vegetation. Once it meets city standards, it goes to a planting strip where it eventually returns to the city’s aquifer.

Challenging the Status Quo

The Bullitt Center’s innovative plumbing and rainwater treatment systems have tested the boundaries of local building codes and jurisdictions. No project has been this advanced in its thinking. The City of Seattle has been working with the design team to provide assistance for other projects looking to use similar systems.

Advancements made through the project include a pilot program to help other projects looking for Living Building certification, the approval of the composting system, and continued work to approve the rainwater treatment system for use as potable water.

Source | Photo: Bullitt Center, jseattle via photopin cc


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Dawn Killough

has over 15 years experience in the construction industry and is the author of Green Building Design 101, an e-book available from Amazon. She is a LEED AP and Certified Green Building Advisor, and has worked on the LEED Certification of three projects in Salem, Oregon.
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