Credit: Stephen Voss
Paula Kehoe is the director of water resources for the San Francisco Public Utilities Commission (SFPUC) and the Vision 2020 chair for Water Efficiency. Sarah Rhodes (not pictured) is a licensed professional engineer and a project manager in the water resources division of SFPUC.
By 2020, we will have recycled our current thinking on water use and supply in order to provide more dynamic, widespread solutions that address the world’s growing need for water in the face of less availability. Worldwide, water consumption has tripled in the last 50 years. According to the United States Environmental Protection Agency (EPA), the United Nations estimates that the world’s population will exceed 9 billion people by 2050 and that the number of people living in urban areas will double, to more than 6 billion. Managing the supply and availability of water is one of the most critical natural resource issues facing the world, and new approaches to urban water supplies are urgently needed.
Diversifying portfolios and reducing the reliance on imported supplies are key to meeting future water demands. While conservation is a core water management strategy, developing new local supplies will also be needed.
Large-scale buildings produce alternate sources such as rainwater, stormwater, foundation drainage, graywater, and blackwater that, following treatment, can meet their own nonpotable water needs. Generally, the major nonpotable indoor water demand in any building is toilet flushing (accounting for approximately 25 percent of residential demand and as much as 75 percent of commercial demand). This need for water, however, can be substantially or fully met through the capture, treatment, and reuse of on-site alternate water sources. Other major applications for nonpotable water include irrigation, cooling and heating applications, and process water. These systems can reduce water use by 50 percent for residential buildings and up to 95 percent for commercial buildings.
Decentralized systems can also increase the resiliency and adaptability of ever-changing urban cores. What’s more, the technology to treat alternate water sources does exist today and, with the latest updates to the Uniform Plumbing Code and the International Construction Code, it is slowly being mainstreamed in the United States. Increased standards also are helping adoption. The recently published NSF/ANSI Standard 350 for on-site water reuse, for example, provides a standard for certifying products that treat on-site graywater and blackwater for nonpotable reuse.
The Cost and Institutional Barriers
On-site water treatment and reuse is being implemented in San Francisco, New York City, Seattle, and Portland, Ore. Overseas, areas within Tokyo and Beijing mandate it for large developments. But this practice is not the norm, and the two biggest barriers to more widespread use are cost and regulatory oversight.
Water rates remain low across the U.S. Therefore, while these systems may add only an incremental cost of 5 percent to a building’s construction budget, the return on investment is long and the systems are often value engineered out of a project. Plumbing can account for up to 95 percent of total costs associated with a nonpotable water system, with the treatment of the water accounting for much less. The high costs are attributed to the dual-plumbing required to separate nonpotable and potable water systems.
Cities may choose to foster these systems, however, through legislation. In San Francisco, dual plumbing has been required since the early 1990s in certain portions of the city designated as recycled-water use areas. In these areas, on-site nonpotable projects are desirable since the dual-plumbing costs would be incurred regardless by locating a project in these areas.
The other significant factor restraining the widespread implementation of distributed water systems is institutional in nature. The lack of public policies and regulatory frameworks creates barriers. Current construction codes incorporate green building and green plumbing alternatives, but these sections often are included as exceptions or supplements and may not be fully adopted by local authorities. In addition, the codes are not intended to address ongoing operation and public health concerns.
In the U.S., there are no overarching national water quality standards for on-site alternative water systems. This lack of national guidance has resulted in each state establishing its own interpretation of the laws, guidelines, and codes. And, from research conducted, many of these water system projects were permitted through a variance or other special regulations and not as part of the normal course of business.
The Path to Innovation
So how do we move forward? Here are a few key steps:
Raise the national water fixture standard. On average, each American uses 100 gallons of water a day at home, almost half of which is for nonpotable purposes such as flushing toilets and washing clothes. Federal standards are lagging behind industry advances for fixture efficiency that are promoted by programs like EPA’s WaterSense and the Consortium for Energy Efficiency. For example, the WaterSense program beats baseline federal standards by 15 to 50 percent for common fixtures such as toilets, urinals, showerheads, and faucets.
Join the green building movement. Consumers are paying rental and sale price premiums for properties that include Energy Star and LEED certifications, and alternative water systems can move from the exception to part of the business model by expanding the credits awarded for lowering potable water use. For example, all green-building certifications could require projects to obtain points for the collection, treatment, and use of alternate water sources. Currently LEED only includes 11 water efficiency points but has 37 energy efficiency points.
Establish a forum for governance. City leaders can establish regulatory frameworks and financing strategies to encourage the widespread application of alternate water sources. San Francisco, for example, resolved its regulatory issues by creating the Non-Potable Water Program, a local program for regulating on-site water use that was codified in September 2012 through a city ordinance. This task involved coordination between three city agencies to provide a streamlined permitting, review, and approval process for on-site system installation and operation. This fall, the city plans to expand the program to allow and encourage district—or multiparcel—water reuse applications. By working together on a district-scale, two or more buildings can aggregate their treatment and reuse of alternate water supplies in order to be able to maximize their water reuse.
On a larger scale, San Francisco is creating the Alliance for Innovation in Urban Water Systems to help cities learn from one another. The alliance, which we at the San Francisco Public Utilities Commission (SFPUC) are launching now, aims to inspire local leadership on alternative water sources, to promote resiliency through decentralized systems, to share success stories, and to support research on sustainable water systems, including appropriate water quality standards and policies.
In order to meet the water demands of 2020 and beyond, we need a new paradigm for urban water management. Networking and cross-collaboration is key. In 2014, SFPUC will host the Innovations in Urban Water Systems Summit to bring together city leaders to better understand the critical role they can play in urban water infrastructure. By encouraging market transformation on the local level, we will make alternative water source use the norm.