When Opportunity Knocks: Background
Building developers, owners and architects are seeking to incorporate greater sustainable construction and operational practices into structures in King County, Washington. Such strategies include ultra-sustainable features such as on-site wastewater treatment systems that are designed to avoid discharging waste into the wastewater collection system for treatment. This type of on-site system is known as a “zero discharge structure” and does not present an environmental or public health risk.
The recently constructed Bullitt Center in Seattle is one such structure - a commercial office building designed and constructed to achieve Living Building Challenge certification, which promotes energy efficiency and recycling waste products on-site, including wastewater. Prior to the Bullitt Center, there was no clear regulatory framework in Seattle for the permitting of an on-site composting system and greywater treatment facility. The Bullitt Center also needed a little extra help in finding the right solution for recycling the waste recovered from the on-site treatment system.
Changing the Code: Working for the Environment
A recent revision of King County Code 28.84.050 provides the opportunity for zero-discharge structures to qualify for a reduced capacity charge.
“We understood why there’d be questions about assessing a capacity charge for 15 years to a building designed for zero discharge into the sewer system,” said assistant WTD Director Sandy Kilroy. “At the same time, King County wanted to make sure that building owners would pay their fair share for infrastructure they might need in an emergency. The recent code changes strike a balance between these issues.”
Waste Not: Making Waste 100-percent pathogen-free
At the Bullitt Center, wastewater falls into two categories: blackwater from composting toilets and greywater from sinks, showers, and other drains. These two waste streams are physically kept separate so they can be treated with the appropriate biological processes. This means that on a day-to-day basis, no waste will enter the sanitary sewage system. The greywater is treated to meet City and State-approved standards in a second-story constructed wetland prior to its infiltration in a street-side planting strip. All solid human waste entering the toilets and urinals will be composted. The Bullitt Center’s 6-story composting toilet system creates a usable soil amendment, but as is the case with many technologies on the forefront, a little extra help is needed to ensure the compost is 100 percent pathogen-free. So King County and others partnered with Bullitt to ensure solids meet State Department of Ecology’s standards for safety and quality.
The solids from the Bullitt Center are delivered to GroCo Inc. in Kent, Wash., to be further composted into a sustainable, nutrient-rich, pathogen-free soil amendment that’s suitable for all uses, including vegetable gardens. GroCo Compost is made with one part Loop® biosolids produced by WTD - and now some of Bullitt Center’s material - mixed with three parts sawdust from local lumber mills.
Declare Certified: Closing the loop by returning carbon and nutrients to soil
GroCo compost is now Declare Certified, meaning that it contains none of the items found on the Living Building Challenge’s Red List of toxic materials. By contributing to GroCo compost, the Bullitt Center continues to meet the strict criteria required to achieve the highest level of sustainability. GroCo provides organic matter to soils and improves the physical properties of both sandy and clayey soils. It is appreciated by gardeners and commercial landscapers for its ability to aerate soil, retain moisture, and produce beautiful blooms. GroCo also helps protect Puget Sound because it helps urban soils retain rainwater like a sponge, which reduces the amount of dirty stormwater flowing into Puget Sound.
Sharing Liquid Assets: Quenching nature’s thirst
The liquid waste from the Bullitt Center’s composting toilets is delivered to King County WTD’s Carnation Treatment Plant. This facility is a highly advanced wastewater treatment system that was built in 2008 to replace failing septic tanks that were harming public health and the environment. The plant itself earned LEED certification from the U.S. Green Building Council in 2009.
Using advanced membrane bioreactor technology to treat wastewater to the highest reuse standards, the reclaimed water produced in Carnation is so clean it is used for wetland enhancement at the nearby Chinook Bend Natural Area. The Chinook Bend Natural Area exists thanks to a King County partnership with Ducks Unlimited to secure grants and make wetland enhancement discharge an environmentally and economically viable discharge opportunity.
Since King County has long embraced sustainability through its creation of resources from wastewater, it was “only natural” to join the Bullitt Foundation in this demonstration of how municipal utilities can meet the demands of a growing population with sustainable innovation.