Oct 14, 2019

Onsite Water Reuse Offers Promise

This article originally appeared in the October 2019 edition of Water & Wastes Digest as "Transformational Water Management."

Integrated water resources management for water scarce areas

Increasing water demand and greater variability of water supplies resulting from climate change, population growth and other stressors are a few of the threats to urban water security. New tools and an integrated water management approach are needed in the face of these 21st century challenges. Understanding the importance of local water supply reliability in meeting these challenges, the San Francisco Public Utilities Commission (SFPUC) is actively embracing integrated water resources management for the development of local water supplies, including water conservation, groundwater, recycled water and onsite water reuse. Matching the right resource to the right use is critical to integrated water resources management because it promotes treating water to the appropriate level that is needed for its end use. 

Onsite Non-Potable Water Reuse Strategies

Onsite non-potable water systems embody this principle and represent a significant opportunity to transform the way water is managed in buildings. For example, onsite water systems can reduce potable water use by approximately 25% in residential buildings and up to 75% in commercial buildings. These systems highlight how technology and innovation can be used to address some of today’s water challenges. 

Led by the efforts of the SFPUC, San Francisco became the first municipality in California to adopt a program that encourages buildings to collect, treat and use water onsite to meet non-potable demands, such as toilet flushing and irrigation. San Francisco’s Onsite Water Reuse Program established a streamlined process for allowing water sources, such as storm water, rainwater, greywater, blackwater and foundation drainage to be reused in commercial, mixed-use and residential buildings. SFPUC first piloted onsite reuse by installing a blackwater treatment system at its headquarters in 2012 for toilet and urinal flushing. The blackwater system reduced its building’s water consumption by 60%. 

With this success, SFPUC supported the implementation of onsite non-potable water systems in other buildings. The first of its kind in California and the U.S., San Francisco’s Onsite Water Reuse Program streamlined the permitting process and established local oversight and management to ensure systems adequately protect public health. Implemented by four city departments, the program is a successful example of investing in collaboration and eliminating barriers to using water more efficiently. The installation and operation of onsite water systems was made mandatory in 2015 for new development projects with a footprint of 250,000 gross sq ft or greater.

The Grander Picture

Above and beyond water savings, onsite water reuse can provide a pathway to achieving multiple benefits. For example, buildings with onsite non-potable water systems can generate environmental and community benefits by integrating urban greening elements, such as wetlands. Second, capturing and reusing alternate water sources, such as rainwater and storm water, provide benefits by reducing runoff from entering combined sewer systems during storm events. Furthermore, onsite water systems optimize resource management by matching the right resource to the right use. Not least of all, integration of onsite water systems with existing infrastructure can provide utilities with the flexibility and resiliency to adapt to future change.  

Outside of San Francisco, communities across the Bay Area and California also are recognizing onsite water systems as a promising approach to sustainable water resources management. Since launching the Onsite Water Reuse Program, SFPUC has lead a larger national effort to advance onsite water reuse. Working alongside the Water Research Foundation, the Water Reuse Assn., and the US Water Alliance, SFPUC chairs the National Blue Ribbon Commission for Onsite Non-potable Water Systems.

This commission brings together water and wastewater utilities and public health agencies from across North America to address challenges and encourage widespread on-site water reuse adoption, including the need for consistent permitting and management approaches as well as the need for consistent water quality standards that are health-risk based. The Blue Ribbon Commission’s work has contributed to a fundamental shift in the perspective of many participating agencies who now have the appropriate framework and tools to develop regulations for onsite water reuse. California, Colorado, Minnesota, Hawaii and Washington D.C. have been able to move forward with regulations or policies supporting onsite reuse within the last four years, while others, including Washington, Oregon, Texas and Alaska are considering similar steps forward.  

Reimagining our urban water systems demands collaboration, consistency and cross-cutting ideas. Utilities have an important leadership role in actively promoting integrated water resources management and building an enabling environment for water supply diversification. By looking to onsite water reuse as an alternative water supply, San Francisco is leading the way in successfully implementing solutions to address today’s pressing water challenges. 

About the author

Paula Kehoe is director of water resources for San Francisco Public Utilities Commission. Taylor Chang is water resources analyst for San Francisco Public Utilities Commission. Kehoe can be reached at [email protected]. Chang can be reached at [email protected].

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