An investigation into the potential of residential graywater use to alleviate water resource challenges in the state of California
An investigation into the potential of residential graywater use to alleviate water resource challenges in the state of California
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Issue Date
2010
Authors
Barnhart, Craig
Orca, Gretchen
Worthy, James
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Abstract
Drought, population growth, climate change, natural disasters, and aging infrastructure continue to challenge California’s water resource management and threaten the ability of the state to provide fresh water resources to meet growing demand. The passage of Senate Bill 1258 in 2008 along with the Department of Housing and Community Development emergency ruling in 2009 brought substantive changes to residential graywater regulation in favor of legalized direct irrigation systems. The rulings set graywater standards and relaxed permitting requirements to encourage adoption by homeowners. This paper explores the viability of wide-scale residential graywater use to alleviate California’s water resource challenges. Environmental and public health and safety concerns of graywater use are addressed along with treatment methods and system design. Case studies and economic analysis of residential graywater system usage for urban landscape irrigation and toilet flushing are reviewed. Residential graywater usage has not been shown to produce health issues during practical application and can save roughly 50% of household potable water usage. Although current utility costs do not economically favor graywater system usage based solely on cost savings to the homeowner, statewide benefits of large-scale adoption may warrant the adoption of public or private incentive programs for graywater users. At a time when California’s centralized treatment infrastructures are nearing the end of their working lifespan, decentralization of water management along with private and public action toward resource conservation and system efficiency are vitally important. Authors conclude that graywater use is an effective and available method to achieve these ends.
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Environmental engineering