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A New Era of Water Management

As the world enters the 21st century, the human community finds itself searching for new paradigms for water supply and management in light of expanding populations, sprawling development, climate change, and the limits of existing conventional supplies. This introductory chapter explores the context for this new era of water management, within which water reuse is attracting increasing attention.

POPULATION GROWTH AND WATER SUPPLY

In the year 1900, the population of the world was between 1.6 and 1.8 billion persons (U.S. Census, 2010e). By the end of the 20th century, it was just short of 6.1 billion persons (U.S. Census, 2010d), an increase of approximately 270 percent. The United States finds itself in the same situation. Between 1900 and 2000, the population of the United States grew from 76 million persons to 282 million persons, an increase of 240 percent (U.S. Census 2010c). Along with this increase in population has come an increase in the demand for water.

To address the water supply needs of this expanding population in the United States, the 20th century was a time for building major water infrastructure, particularly dams (Figure 1-1) and aqueducts (Morgan, 2004). In the southwestern United States, ambitious projects built on the Colorado River, the Central Valley of California, and in central Arizona provided water and power that supported rapid population growth and increases in irrigated agriculture. Smaller projects in Texas, Florida, Colorado, and Georgia also expanded the nation’s water supply capacity as population growth accelerated. Although a limited number of water supply and storage projects are still being built, the rate of construction of water supply infrastructure has dropped off significantly in recent decades (Graf, 1999; Gleick, 2003).

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FIGURE 1-1 Reservoir capacity in the continental United States from 1900 to 1996.
SOURCE: Data from Graf (1999).

This decline in construction of new capacity has occurred in spite of continuing projections for increased demand, suggesting that the strategy of fulfilling increased water demand by building large dams and aqueducts to capture water from freshwater streams is reaching its limit. This change is attributable to a number of causes, among them: (1) a diminishing number of rivers whose flow is not already claimed by other users, (2) increased concern about adverse impacts of



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1 A New Era of Water Management As the world enters the 21st century, the human 900 Total U.S. Reservoir Storage community finds itself searching for new paradigms for 800 water supply and management in light of expanding 700 (in millions of acre-feet) populations, sprawling development, climate change, 600 and the limits of existing conventional supplies. This 500 introductory chapter explores the context for this new 400 era of water management, within which water reuse is 300 attracting increasing attention. 200 100 POPULATION GROWTH 0 AND WATER SUPPLY 1980 2000 1900 1920 1940 1960 FIGURE 1-1 Reservoir capacity in the continental United States In the year 1900, the population of the world was from 1900 to 1996. between 1.6 and 1.8 billion persons (U.S. Census, SOURCE: Data from Graf (1999). 2010e). By the end of the 20th century, it was just short of 6.1 billion persons (U.S. Census, 2010d), an increase Texas, Florida, Colorado, and Georgia also expanded of approximately 270 percent. The United States finds the nation’s water supply capacity as population growth itself in the same situation. Between 1900 and 2000, accelerated. Although a limited number of water sup- the population of the United States grew from 76 mil- ply and storage projects are still being built, the rate of lion persons to 282 million persons, an increase of 240 construction of water supply infrastructure has dropped percent (U.S. Census 2010c). Along with this increase off significantly in recent decades (Graf, 1999; Gleick, in population has come an increase in the demand for 2003). water. This decline in construction of new capacity has To address the water supply needs of this expand- occurred in spite of continuing projections for increased ing population in the United States, the 20th century demand, suggesting that the strategy of fulfilling was a time for building major water infrastructure, increased water demand by building large dams and particularly dams (Figure 1-1) and aqueducts (Morgan, aqueducts to capture water from freshwater streams is 2004). In the southwestern United States, ambitious reaching its limit. This change is attributable to a num- projects built on the Colorado River, the Central Valley ber of causes, among them: (1) a diminishing number of California, and in central Arizona provided water of rivers whose flow is not already claimed by other and power that supported rapid population growth and users, (2) increased concern about adverse impacts of increases in irrigated agriculture. Smaller projects in 9

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10 WATER REUSE impoundments on stream ecology, and (3) a better western United States where shifts in the timing and understanding of water quality problems caused by ir- location of precipitation and decreases in snowfall are rigated agriculture (NRC, 1989). expected (NRC, 2007). Regional development and migration have placed Considerable uncertainty remains about the im- further stress on our water sources. Large populations pacts of climate change on water supplies. Improve- have migrated to warmer climates in California, Ne- ments in models and the collection of additional data vada, Arizona, Texas, and Florida, causing growth rates are likely to reduce the uncertainties associated with of 85 percent to more than 400 percent between 1970 these estimates in coming decades. However, the pres- and 2009 in those states while the national population sures placed on water supplies by the combination of has increased by less than 50 percent (Figure 1-2). In population growth and the likely impacts of climate some places, these changes have necessitated infrastruc- change necessitate a reexamination of the ways in ture to collect and move water on a grand scale (e.g., which water is acquired and used, before all of the ques- the infrastructure on the Colorado River, the California tions about climate change impacts on the hydrological State Water Project, and the Central Arizona Project). cycle are resolved (NRC, 2011a). An even broader perspective on this migration is provided in the U.S. county-level population pro- NEW APPROACHES TO jections through 2030 prepared by the U.S. Global WATER MANAGEMENT Change Research Program (Figure 1-3). Continued development of these population centers in the south- The increase in population coupled with the de- west and arid west and continued migration from creased rate of construction of reservoirs, dams, and population centers in the eastern and midwestern other types of conventional water supply infrastructure United States will require substantial transformation in is leading to a new era in water management in the the way water is procured and used by the people who United States. The pressures on water supplies are live and work in these geographies. changing virtually every aspect of municipal, industrial, The shift in population and associated water de- and agricultural water practice. These changes in water mand is further complicated by potential impacts of management strategies take two principal forms: reduc- climate change on the water cycle. Increases in evapo- ing water consumption through water conservation and transpiration due to higher temperatures will increase technological change and seeking new sources of water. water use for irrigated agriculture and landscaping while changes in precipitation patterns (see Figure 1-4) Reducing Water Consumption may diminish the ability of existing water infrastructure to capture water. This is particularly important in the Improvements in water efficiency and programs for water conservation have begun to change our national water use habits, reducing per capita water consump- tion. More changes of this kind are likely in the future NV across many sectors. In Table 1-1, selected data on wa- ter use collected by the U.S. Geological Survey (Kenny AZ et al., 2009) are summarized, where changes in water FL use by both agriculture and industry are clearly evident. While the U.S. population grew from roughly TX 150 million to 300 million persons during the 60- CA year period, industrial water use—an application that was once the third highest use of water in the United U.S. States—grew only modestly between 1950 and 1970 0% 100% 200% 300% 400% 500% and has been on the decline for 45 years now. These Increase in Population, percent decreases are due to increased efficiency, higher prices FIGURE 1-2 Population growth in selected states between 1970 and 2009. for water and energy, and a shift away from water- SOURCE: Data from U.S. Census (2010b).

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11 A NEW ERA OF WATER MANAGEMENT FIGURE 1-3 County-level population growth trends in the United States between 1970 and 2030. Each block on the map illustrates one county in the United States. The height of each block is proportional to that county’s population density in the year 2000, and so the volume of the block is proportional to the county’s total population. The color of each block shows the county’s projected change in population between 1970 and 2030, with shades of orange denoting increases and blue denoting decreases. SOURCE: USGCRP (2000). intensive manufacturing. More recently transfer of manufacturing outside the United States may also have been important. Water use for irrigation peaked in 1980 and has now declined below 1970 levels. New technologies have been developed in irrigation practice (Gleick, 2003) and indications are that these technologies, if more widely adopted, could result in significant addi- tional improvement (Postel and Richter, 2003). Water exchanges between municipal and agricultural entities are also taking place with increasing frequency. Agree- ments with agricultural interests by both the Metro- FIGURE 1-4 Downscaled climate projections showing the politan Water District of Southern California and the change in 30-year mean annual precipitation between 1971– San Diego Water Authority are examples. This practice 2000 and 2041–2070, in centimeters per year. The median puts further pressure on agriculture to get value for the difference is based on 112 projections. water it uses. SOURCE: Brekke et al. (2009). R02129 Figure 1-4 bitmapped

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12 WATER REUSE TABLE 1-1 Summary of Water Use (billion gallons per day) in the United States, 1950–2005 Self- Other Total Public Supplied Livestock, Thermoelectric Industrial (Excluding Year Supply Domestic Irrigation Aquaculture Power Use Use Power Use) 1950 14.0 2.1 89 1.5 40 37 144 1955 17.0 2.1 110 1.5 72 39 170 1960 21.0 2.0 110 1.6 100 38 173 1965 24.0 2.3 120 1.7 130 46 194 1970 27.0 2.6 130 1.9 170 47 209 1975 29.0 2.8 140 2.1 200 45 219 1980 33.0 3.4 150 2.2 210 45 234 1985 36.4 3.3 135 4.5 187 30.5 210 1990 38.8 3.4 134 4.5 194 29.9 211 1995 40.2 3.4 130 5.5 190 29.1 208 2000 43.2 3.6 129 6.0 195 23.2 205 2005 44.2 3.8 128 10.9 201 22.2 209 NOTE: Includes both freshwater and saline water sources. SOURCE: Data from Kenny et al. (2009). Thermoelectric power use also peaked in 1980, but 700 this use is misleading because a large fraction consists of “once-through” cooling water, which is primarily a 600 nonconsumptive use (Kenny et al., 2009). Thus, reduc- Public Supply Per Capita Water Use, gal/cap/day 500 tion of use of this water would not necessarily provide Self-Supplied Domestic new water resources, although it may have other en- Irrigation 400 vironmental benefits. Furthermore, plants employing Livestock, Aquaculture freshwater once-through cooling are often located in Other Industrial Use 300 areas with ample water resources where water demands are not growing rapidly. 200 Whereas the total consumption for industry and irrigation have both decreased in recent decades, water 100 use for primarily public supply continues to rise. Dur- 0 ing the period between 1950 and 2005, water used 1955 1965 1975 1985 1995 2005 for public supply more than tripled as the nation’s population doubled. Much of the increase in per capita FIGURE 1-5 Past trends in water use in the United States, consumption of water during this period (most nota- expressed on a per capita basis. SOURCE: Data from Kenny et al. (2009). bly between 1950 and 1985) can be tied to increased water use for landscaping, especially in arid climates. Consequently, there is significant potential for water decline (Figure 1-5). Per capita industrial water use conservation in the public supply sector. has been on the decline since 1965; per capita agri- Overall, U.S. water use (excluding thermoelectric cultural use was flat between 1955 and 1980 and has power uses) has been stable at approximately 210 bil- been declining since then. Municipal use (referred to as lion gallons per day (BGD; 795 million cubic meters public water supply in Kenny et al., 2009) continued to per day [m3/d]) since 1985. This flat water-use trend grow until 1990, but even this sector has begun to see corresponds with the slowdown in construction of new the effects of water conservation in recent years. It is impoundments in the United States (Figure 1-1). reasonable to expect that conservation will continue to When these water use data are combined with play an increasingly important role in the nation’s water population data from the U.S. Census Bureau and management in the decades ahead, thereby reducing examined on a per capita basis, it becomes clear that the demand for new water supplies. Including all sec- irrigation and nonpower industrial use are now on the tors (except thermoelectric power), per capita water

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13 A NEW ERA OF WATER MANAGEMENT 1200 500 450 1000 400 Per capita use, gal/cap-d Total U.S. Water Use (BGD) Population, millions 800 350 600 300 250 400 ? 200 200 150 100 0 1950 1970 1990 2010 2030 2050 FIGURE 1-6 Changes in U.S. water use and implications for the future. Population and total U.S. water use shown on left axis; per capita water use on right axis. Per capita water use includes all water uses except thermoelectric power, which is dominated by once-through cooling. SOURCE: Data from Kenny et al. (2009) and U.S. Census Bureau (2008). Searching for New Water Sources use was relatively stable between 1950 and 1980 but has dropped precipitously since that time (Figure 1-5). In addition to conservation efforts, the other major The U.S. Census Bureau predicts that the nation’s emphasis in the new era of water management involves population will increase by over 50 percent between a search for untapped water sources. These sources 2010 and 2060. This population growth is displayed in include the desalination of seawater and brackish Figure 1-6 along with the history of total water use and groundwater, the recovery of groundwater impaired the history of per capita water use as well. If the U.S. by previous anthropogenic activity, off-stream or un- Census estimates are correct, then, barring the develop- derground storage of seasonal surpluses from existing ment of major new water sources, per capita use must impoundments, the recovery of rainwater and storm- decline further. Both more efficient water use and the water runoff, on-site greywater1 reuse, and the reuse of development of new sources of water beyond those the nation has traditionally used may be necessary in areas with limited existing water supplies. 1 Greywater is water from bathing or washing that does not contain concentrated food or human waste.

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

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15 A NEW ERA OF WATER MANAGEMENT flows need to take some allowance for reductions in wastewater production due to conservation and reduced sewer flows during future periods of water restriction. Although a map depicting the location of all of the effluent discharges in the country is not available, the distribution of wastewater discharges should roughly track the population distribution, assuming similar per capita domestic and industrial wastewater generation rates occur across the country (Figure 1-8). Figure 1-8 illustrates that much of the nation’s wastewater is dis- charged to inland waterways. As a result, de facto reuse of wastewater is already an important part of the current water supply portfolio. The ongoing practice of de facto FIGURE 1-7 Reduction in per capita flow to the Los Angeles reuse and the likelihood that all of the reclaimed water County Joint Outfall during the beginning of the 21st century will not be returned to the water supply also means (2000–2007). SOURCE: Data from S. Highter, Los Angeles County Sanitation that increased water reuse will not necessarily increase District, personal communication, 2010. the nation’s net water resource by an equal amount. In fact in many western U.S. jurisdictions, downstream users possess a water right that could prevent or inhibit water system (e.g., when downstream drinking water municipal reuse (see Chapter 10). systems use surface waters that receive upstream waste- Based on data provided by the U.S. Environmental water discharges). In the committee’s view, the use of Protection Agency (EPA, 2008c), the committee calcu- effluent-impacted water supplies is reuse in fact, if not lated that approximately 12 BGD (45 million m3/d) of reuse in name. Therefore, the committee will refer to U.S. municipal wastewater was discharged directly into the less carefully scrutinized practice of using effluent- or just upstream of an ocean or estuary in 2008 out of impacted water supplies for potable water sources as 32 BGD (120 million m3/d) discharged nationwide (38 “de facto” reuse, rather than the term unplanned reuse percent).4 Because there are no downstream cities that (see Chapter 2 for more discussion of de facto reuse). rely on these discharges to augment their water sup- Municipal wastewater effluent is produced from plies, reuse of coastal discharges could directly augment households, offices, hospitals, and commercial and the nation’s overall water resource. If all of these coastal industrial facilities and conveyed through a collection discharges were reused, the additional water available system to a wastewater treatment plant. In 2004, over would represent approximately 6 percent of estimated 16,000 publicly owned wastewater treatment plants U.S. total water use or about 27 percent of municipal were in operation in the United States, receiving over use in 2005 (Kenney et al., 2009). However, not all of 33 BGD (120 million m3/d) of influent flow (EPA, the water available for reuse is located in areas where 2008b). These publicly owned wastewater plants serve it is needed. Additionally, the health of some coastal approximately 222 million Americans, or 75 percent estuaries may be dependent on the freshwater inflows of the population. Thus, the total discharge averages provided by coastal wastewater discharges, particularly approximately 150 gallons (0.56 m3) per day per per- in water-scarce regions. Thus, the extent of availability son.3 Recently, however, per capita wastewater flows have been decreasing, largely because of conservation practices (see Figure 1-7 for one example). Thus, water R02129 4 The raw data of the wastewater treatment plants along the conservation and water reuse are linked, and projections continental U.S. coastline is from EPA’s Clean Watersheds Needs Figure 1-7 Survey: 2008 Data and Reports. The cited numbers are the sum of of water available for bitmapped today’s wastewater reuse based on the outflow from wastewater treatment plants that discharge into watersheds having a fourth-level hydrologic unit code–defined area 3 Calculated from 33 BGD divided by 222 million people. Thus, that directly borders or is immediately upstream of a major estuary this per capita discharge includes all discharges to wastewater treat- or ocean, such that the wastewater discharge is unlikely to be part ment plants, not just residential discharges. of the water supply of any downstream users.

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16 WATER REUSE FIGURE 1-8 Distribution of the U.S. population in 2009, which can be used to approximate discharge volumes of municipal waste- water effluent. SOURCE: U.S. Census Bureau (http://www.census.gov/popest/gallery/maps/PopDensity_09.pdf). of these coastal discharges for reuse would be depen- the low-hanging fruit,” through practices such as ir- dent on site-specific analysis. rigating golf courses, landscapes, municipally owned If reclaimed water was used largely for noncon- parks, and medians near wastewater treatment plants sumptive uses, the water supply benefit of water reuse or by converting industrial applications that are less could be even greater because, in many cases, the waste- sensitive to water quality (e.g., cooling) to reclaimed water can be again captured and reused. It is also evi- water. Where these projects have been implemented, dent that many inland discharges could be productively communities have become familiar with the advantages used as well, suggesting the potential for an even larger of reuse, particularly improved reliability and drought impact from water reuse on the nation’s water supplies. resistance of the water supply and reduced nutrient loading to sensitive downstream ecosystems. On the other hand, while many of these initial types of water CURRENT CHALLENGES reuse projects were inexpensive and relatively simple to Important challenges remain that must be ad- implement, many future water reclamation projects are dressed before the potential of municipal water reuse likely to pose greater challenges. can be fully harnessed. These challenges are discussed In addition, utilities will have to consider public in this section and explored in more depth in the re- skepticism about the health risks associated with re- mainder of the report. use projects, and the public decision-making process It is important to recognize that many communities can be a difficult one, particularly for projects with a currently practicing water reuse have already “picked potable reuse component. People have been trained

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17 A NEW ERA OF WATER MANAGEMENT for generations to provide separation in both time and remove it, and no one treatment technique or combina- space between their wastes and their water supplies, tion of treatment techniques can be relied upon to re- and therefore the public is concerned about the safety duce all possible contaminants to levels below the limits of using wastewater effluent for domestic purposes. At of detection. Robust analytical methods will continue the same time, several high-profile reports detailing the to be developed that will detect organic compounds presence of pharmaceuticals and personal care products and pathogens at increasingly lower levels. Thus, water in water supplies (e.g., Kolpin et al., 2002; Benotti et managers are faced with the challenge of knowing a al., 2009) have increased awareness of the common contaminant is present at low levels without knowing practice of de facto water reuse, which has increased if its presence at those levels is significant. with population growth. Today, many U.S. communi- In the decades since the NRC published its ties rely on drinking water sources that are exposed to groundbreaking report Risk Assessment in the Federal wastewater discharges. Nevertheless, the quality of U.S. Government: Managing the Process (NRC, 1983), the drinking water continues to improve, largely because nation has developed a sophisticated infrastructure for of improvements in treatment technology. Perhaps the assessing the risk of anthropogenic chemicals in the en- question is not whether reuse should be considered; vironment and a significant cadre of experts trained in rather the question should be how reuse can be planned its application. Significant progress also has been made so that it better incorporates appropriate engineered in the assessment of risks from waterborne pathogens. barriers. In many cases the alternative to building new, W hereas this infrastructure is well suited for the sup- engineered water reuse systems is increased reliance on port of national regulations designed to manage risk de facto water reuse, with fewer engineered controls and also for application to the assessment of important and monitoring. regional decisions, it is not as well suited to facilitate A century ago, circumstances as well as best profes- the decisions of individual communities comparing the sional judgment supported policies in which water was costs, risks, and benefits of planned reuse with other considered to be potable after it spent a certain period water supply alternatives. Thus, communities face of time in the natural environment. This is illustrated challenges in finding adequate technical support for by an official policy of the state of Massachusetts allow- complex water management decisions. ing sewage (untreated wastewater) discharges to rivers serving as a drinking water supply provided the outfall STATEMENT OF COMMITTEE was located more than 20 miles (32 km) upstream of TASK AND REPORT OVERVIEW the drinking water intake (Hazen, 1909; Sedgwick, 1914; Tarr, 1979). Today, we increasingly rely on the The challenges discussed in the previous section application of treatment technologies and sophisti- have limited the application of water reuse in the cated monitoring to ensure that safe drinking water United States. In 2008, the NRC’s Committee on As- conditions are achieved. In recent decades, advances sessment of Water Reuse as an Approach for Meeting in the capability of water treatment systems have been Future Water Supply Needs was formed to conduct a substantial, and these systems are now able to routinely comprehensive study of the potential for water reclama- achieve a level of protection that exceeds anything tion and reuse of municipal wastewater to expand and imaginable in the middle of the 20th century. Despite enhance the nation’s available water supply alternatives. this progress, how do we determine when treated Effluent reuse has long been a topic of discussion and wastewater has reached the point where it has become the NRC has issued several reports on the subject in suitable for potable supply? How can this decision be the past (see Box 1-2). made in a way that engenders public confidence? What This broad study considers a wide range of uses, monitoring tools are needed to provide assurance that including drinking water, nonpotable urban uses, irri- promised performance is being delivered on a continu- gation, industrial process water, groundwater recharge, ous basis? and water for environmental purposes. The study also Every treatment technique takes advantage of the considers technical, economic, institutional, and social specific properties of each contaminant in order to challenges to increased adoption of water reuse to pro-

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18 WATER REUSE BOX 1-2 NRC Reports Relating to Water Reuse At least seven NRC reports over the last 30 years have addressed water reuse or related technologies: • Quality Criteria for Water Reuse (NRC, 1982) provided advice for assessing the suitability of water from impaired sources such as wastewater. The report addressed chemical and microbiological contaminants in reclaimed water, health effects testing for reclaimed water, sample concentration methods, and monitoring strategies. It also contained an assessment and criteria for potable water reuse. • The Potomac Estuary Experimental Water Treatment Plant (NRC, 1984) assessed the U.S. Army Corps of Engineers’ operation, maintenance, and performance of the experimental water treatment plant using an impaired water source containing treated wastewater. The report praised the Corps for development of a database of microbiological contaminants and toxicological indicators and for demonstrating the reliability of advanced treatment processes. The report, however, questioned whether there was enough data to ensure protected public health and concluded that failure to detect viruses cannot be accepted as an indication that they are absent. • Ground Water Recharge Using Waters of Impaired Quality (NRC, 1994a) addressed issues concerning identification of potentially toxic chemicals and the limits of natural constituent removal mechanisms. Public health was the principal concern of the committee, and constant monitoring as well as federal leadership were identified as crucial steps if groundwater recharge using impaired waters is to be used. The com- mittee recommended significant further research in both epidemiology and toxicology to assess appropriate risk limits and to identify emerging contaminants. • Use of Reclaimed Water and Sludge in Food Crop Production (NRC, 1996) examined the safety and practicality of using treated municipal wastewater and sewage sludge for production of crops for human consumption. The report concluded that risks from organic compounds were negligible, and Class A water standards appeared to be adequate to protect human health. The committee’s concerns were primarily demand-side; acceptance from farmers and consumers was expected to be a much larger hurdle for significant use of reclaimed water in food crops. • Issues in Potable Reuse (NRC, 1998) provided technical and policy guidance regarding use of treated municipal wastewater as a potable water supply source. The committee recommended the most protected source be targeted first for use, combined with nonpotable reuse, con - servation, and demand management. While direct potable reuse is not yet viable, indirect potable reuse may be viable when careful, thorough, project-specific assessments are completed, including monitoring, health and safety testing, and system reliability evaluation. • Prospects for Managed Underground Storage (NRC, 2008c) identified research, education needs, and priorities in managed underground storage technology and implementation. The report concluded that better knowledge of contaminants in water and chemical constituents in the subsurface and a systematic way to deal with emerging contaminants are needed. The report stated that technologies such as ultraviolet, ozone, and membranes can be made more efficient, and new surrogates or indicators may be needed to monitor for a wider suite of contaminants. • Desalination: A National Perspective (NRC, 2008b) assessed the state of the art in desalination technologies and addressed cost and implementation challenges. Several of the technologies discussed in the report, such as reverse osmosis and concentrate disposal, are also relevant to water reuse. vide practical guidance to decision makers evaluating The committee was specifically tasked to address their water supply alternatives. The study is sponsored the following questions: by the EPA, the Bureau of Reclamation, the National 1. Contributing to the nation’s water supplies. Science Foundation, the National Water Research Institute, the Centers for Disease Control and Pre- W hat are the potential benefits of expanded water reuse vention, the Water Research Foundation, the Orange and reclamation? How much municipal wastewater County Water District, the Orange County Sanitation effluent is produced in the United States, what is its District, the Los Angeles Department of Water and quality, and where is it currently discharged? What is Power, the Irvine Ranch Water District, the West Basin the suitability—in terms of water quality and quan- Water District, the Inland Empire Utilities Agency, the tity—of processed wastewaters for various purposes, Metropolitan Water District of Southern California, including drinking water, nonpotable urban uses, ir- the Los Angeles County Sanitation District, and the rigation, industrial processes, groundwater recharge, Monterey Regional Water Pollution Control Agency. and environmental restoration?

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19 A NEW ERA OF WATER MANAGEMENT 2. Assessing the state of technology. W hat task is addressed in nine subsequent chapters of this report: is the current state of the technology in wastewater treatment and production of reclaimed water? How • Chapter 2 provides context for this report by do available treatment technologies compare in terms describing the history of reuse, common reuse applica- of treatment performance (e.g., nutrient control, con- tions, and the use of reuse technologies in the United taminant control, pathogen removal), cost, energy use, States and globally. and environmental impacts? What are the current • Chapter 3 discusses water quality and contami- technology challenges and limitations? What are the nants of concern in wastewater effluent. infrastructure requirements of water reuse for various • Chapter 4 provides an overview of the state of purposes? 3. Assessing risks. W hat are the human health the science in water reuse with respect to treatment technology. risks of using reclaimed water for various purposes, • Chapter 5 examines design and operational including indirect potable reuse? What are the risks strategies to ensure reclaimed water quality. of using reclaimed water for environmental purposes? • Chapter 6 discusses the risk assessment frame- How effective are monitoring, control systems, and the work as it applies to water reuse. existing regulatory framework in assuring the safety • Chapter 7 explores the risks of reuse in context and reliability of wastewater reclamation practices? 4. Costs. How do the costs (including environ- by evaluating the relative risks of various reuse practices to human health compared with de facto reuse practices mental costs, such as energy use and greenhouse gas that are generally perceived as safe. emissions) and benefits of water reclamation and reuse • Chapter 8 discusses applications of water reuse generally compare with other supply alternatives, such for ecological enhancement. as seawater desalination and nontechnical options such • Chapter 9 examines the financial and economic as water conservation or market transfers of water? 5. Barriers to implementation. W hat imple- circumstances surrounding reuse and examines the benefits of reuse. mentation issues (e.g., public acceptance, regulatory, • Chapter 10 describes the social and institutional financial, institutional, water rights) limit the appli- factors, including regulatory concerns, legal consider- cability of water reuse to help meet the nation’s water ations, and public perception. needs and what, if appropriate, are means to overcome • Chapter 11 discusses actions needed to advance these challenges? Based on a consideration of case stud- the capacity to use reuse to address water demands, ies, what are the key social and technical factors associ- including research needs and the roles of federal and ated with successful water reuse projects and favorable nonfederal agencies. public attitudes toward water reuse? Conversely, what are the key factors that have led to the rejection of some Note that this report covers all types of reuse, but water reuse projects? 6. Research needs. W hat research is needed to not all chapters include equal coverage of all reuse ap- plications. The committee has chosen to focus more advance the nation’s safe, reliable, and cost-effective intensely on applications for which there are specific reuse of municipal wastewater where traditional sources unresolved issues that may be limiting the ability of of water are inadequate? What are appropriate roles for communities and local decision makers to make wise governmental and nongovernmental entities? choices about their future water supply options; thus, the reader will find greater discussion on potable reuse The committee’s report and its conclusions and recom- relative to nonpotable reuse. Additionally, on the basis mendations are based on a review of relevant technical of the statement of task, the committee focused its ef- literature, briefings, and discussions at its eight meet- forts on the reuse of municipal wastewater effluent. The ings, field trips to water reuse facilities, and the experi- issues discussed in the report have applicability to both ence and knowledge of the committee members in their large and small municipal wastewater treatment plants. fields of expertise. Following this brief introduction, the statement of

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20 WATER REUSE million m3/d) is discharged to an ocean or estuary However, the committee does not discuss building- scale reuse or greywater reuse in depth in this report. (equivalent to 6 percent of the estimated total U.S. water use or 27 percent of public supply). Reuse of these coastal discharges, where feasible, in water-limited re- CONCLUSION gions could directly augment available water resources. As populations are increasing, particularly in wa- W hen reclaimed water is used for nonconsumptive ter-limited regions, water managers are looking toward uses, the water supply benefit of water reuse could be sustainable water management solutions to address even greater if the water can again be captured and shortfalls in supply from conventional water sources. reused. Inland effluent discharges may also be available Efforts to increase the efficiency of water use through for water reuse, although extensive reuse has the poten- enhanced conservation and improved technologies and tial to affect the water supply of downstream users and the development of new sources of water may both be ecosystems (e.g., in-stream habitats, coastal estuaries) in water-limited settings. Municipal wastewater reuse, necessary to address future water demand in areas fac- therefore, offers the potential to significantly increase ing extreme water shortfalls. Potable and nonpotable the nation’s total available water resources. However, reuse are attracting increasing attention in the search for untapped water supply sources. Out of the 32 BGD reuse alone cannot address all of the nation’s water sup- (121 million m3/d) of municipal wastewater effluent ply challenges, and the potential contributions of water discharged nationwide, approximately 12 BGD (45 reuse will vary by region.