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Spahr, Katie ¹

¹ University of ŷ���ڱ���Ƶ

One of the easiest and most practical ways to address future freshwater needs is to implement water conservation. By improving the efficiency of current infrastructure, communities become more resilient to water demand changes like drought and population growth. For urban areas, like Boulder, ŷ���ڱ���Ƶ, where the majority of water is used for indoor residential purposes, the implementation of residential-level water conservation programs can prove to be one of the most effective means for demand management. One way residences can experience water savings is by installing fixtures like low flow showerheads, faucet aerators, and/or water smart dishwashers, which can result in a reduction of indoor water use of up to 35%.

When evaluating indoor residential water use, the highest use is for toilets, which account for approximately 30% of all indoor uses in Boulder. Reducing the amount of potable water used to flush toilets can result in the biggest “bang for your buck” water savings. Toilet flushing was one of the most consistent and predictable water uses found during a residential water use study in Boulder. While installing more efficient toilets can reduce the amount of potable water used to flush and can result in significant water savings, the overall conundrum of using drinking water quality water to flush away human waste still remains. To optimize toilet water use, flushing water can be augmented with treated graywater. Graywater is typically defined as the wastewater from bathtubs, showers, sinks, and laundry machines. This water can be treated to an appropriate quality and reused inside a residence. Replacing graywater for potable water in toilets would convert the 30% indoor use to 30% savings.

Williams Village North is a 500-bed residence hall on the east end of the University of ŷ���ڱ���Ƶ of Boulder Campus provides a case study for a large-scale recirculation system. Graywater is collected from the 65 sinks and 45 showers in the northwest wing and piped to a water treatment train. The graywater is then treated to a high quality and fed through purple pipes to flush the entire building’s 105 toilets. Given the installed system and existing supportive plumbing infrastructure, this presentation will addresses some of the non-technical components of starting and operating a graywater recirculation system in the setting of Boulder, ŷ���ڱ���Ƶ. These components include water use estimates, evaluation of prior appropriation water rights, and the evaluation of environmental impacts of graywater recirculation and, conversely, demand management.

"Water Use Statistics." Drinktap.org. American Water Works Association. Web. 12 Mar. 2012. .

Mayer, Peter W., et al. Residential End Uses of Water. Tech. Denver: AWWA Research Foundation, 1999. Print.