municipal wastewater effluent. The role of each of these approaches in the nation’s future water supply portfolio is likely to be dictated by considerations related to public health, economics, impacts on the environment, and institutional considerations. The NRC recently published studies on desalination (NRC, 2008b), stormwater management (NRC, 2009c) and underground storage (NRC, 2008c). In this new water era, the reuse of municipal effluent for beneficial purposes may also be important. This topic—herein termed water reuse—is the focus of this report. See Box 1-1 for additional reuse terminology.
The terminology associated with treating municipal wastewater and reusing it for beneficial purposes differs within the United States and globally. For instance, although the terms are synonymous, some states and countries use the term reclaimed water and others use the term recycled water. Similarly, the terms water recycling, and water reuse, have the same meaning. In this report, the terms reclaimed water and water reuse are used. Definitions for these and other terms are provided below.
Reclaimed water: Municipal wastewater that has been treated to meet specific water quality criteria with the intent of being used for beneficial purposes. The term recycled water is synonymous with reclaimed water.
Water reclamation: The act of treating municipal wastewater to make it acceptable for beneficial reuse.
Water reuse: The use of treated wastewater (reclaimed water) for a beneficial purpose. Synonymous with the term wastewater reuse.
Potable reuse: Augmentation of a drinking water supply with reclaimed water.
Nonpotable reuse: All water reuse applications that do not involve potable reuse (e.g., industrial applications, irrigation; see Chapter 2 for more details).
De facto reuse: a situation where reuse of treated wastewater is in fact practiced, but is not officially recognized (e.g., a drinking water supply intake located downstream from a wastewater treatment plant discharge point).
SOURCE: These definitions are taken from Crook, 2010.
During the past several decades, treated wastewater (also called reclaimed water) has been reused to accomplish two primary purposes: (1) to create a new water supply and thereby reduce demands on limited traditional water supplies and (2) to prevent ecological impacts that can occur when nutrient-rich effluent is discharged into sensitive environments.2 Increasingly, the basic need for additional water supply is becoming the central motivator for water reuse. In addition to growing water demands, the further adoption of water reuse will be affected by a variety of issues, including water rights, environmental concerns, cost, and public acceptance.
The context for water reuse and common reuse applications for nonpotable reuse (e.g., water reuse for irrigation or industrial purposes) and potable water reuse (e.g., returning reclaimed water to a public water supply) are described in detail in Chapter 2. Potable reuse is commonly broken into two categories: indirect potable reuse and direct potable reuse. This classification considered potable reuse to be “indirect” when the reclaimed water spent time in the environment after treatment but before it reached the consumer. Inherent in this distinction was the idea that the natural environment (or environmental buffer, discussed in Chapter 2) provided a type of treatment that did not occur in engineered treatment systems. An example of these definitions can be found in the NRC (1998) report, Issues in Potable Reuse. The committee has chosen not to use these terms but rather to speak about the project elements required to protect public health when potable reuse is contemplated and to try to understand the attributes of the protection provided by an environmental buffer (see Chapters 2, 4, and 5).
In NRC (1998) a distinction was also made between “planned” and “unplanned” potable water reuse. For this report, the committee has chosen not to use these terms, because they presume that water managers are unaware of the integrated nature of the nation’s
2 For example, the water reuse program in St. Petersburg, Florida, was started in response to state legislation in 1972 (the Wilson-Grizzle Act) requiring all wastewater treatment plants discharging to Tampa Bay to either upgrade to include advanced wastewater treatment (including nutrient removal) or to cease discharging to Tampa Bay (Crook, 2004).