Why should we turn to Net Zero water?
What Is a Net Zero Water Building?
A net zero water building (constructed or renovated) is designed to:
- Minimize total water consumption
- Maximize alternative water sources
- Minimize wastewater discharge from the building and return water to the original water source.
The goal of net zero water is to preserve the quantity and quality of natural water resources with minimal deterioration, depletion, and rerouting of water by utilizing potential alternative water sources and water efficiency measures to minimize the use of supplied freshwater. This principle can be expanded to the campus level.
Ultimately, a net zero water building (or campus) completely offsets water use with alternative water plus water returned to the original water source.
However, if the building is not located within the watershed or aquifer of the original water source, then returning water to the original water source will be unlikely. In those cases, the option for net zero water strategy would depend on alternative water use.
CASE STUDY – BULITT CENTER
Bulding Location: Seattle, Washington,United States
Construction Type: New Construction (including public and academic buildings)
Market Sector: Private
Building Type: Office
Delivery Method: Integrated Project Delivery
Total Building Cost: $30 million
Project Completion Date / Date Building Occupied: April 2013
Approximately 69% (128,800 gallons) of the annual rainwater runoff is collected, stored in a 56,000 gallon cistern, treated, and used for potable and non-potable (approx. 11,400 gallons per year) uses; the remaining 31% will be discharged as storm water, ensuring the integrity of downstream hydrology. Approximately 100,600 gallons of grey water will be treated and evaporated/infiltrated onsite. Through a combination of infiltration, evaporation on the membrane roofing evapotranspiration on the green roofs, and piped discharge, the building closely mimics the historic hydrology of the site. The system supplies all non-potable water for building fixtures and is designed to meet all potable water needs when (pending) permits allow the building to use rainwater to supply 100% of its water needs. Human waste from foam flush toilets and urinals is delivered through piping to 10 basement composting units, where wood chips manage moisture levels and consistent temperatures (135°F to 165°F) ensure pathogens and contaminants are sterilized or killed. Each composter produces approximately 90 gallons (12 cubic feet) of compost each year. This valuable resource is taken to a nearby composting facility to be incorporated with other composted material, and used as a soil amendment.