Desalination and Membrane Technologies:
Federal Research and Adoption Issues

Nicole T. Carter
Specialist in Natural Resources Policy
January 8, 2013
Congressional Research Service
7-5700
www.crs.gov
R40477
CRS Report for Congress
Pr
epared for Members and Committees of Congress

Desalination and Membrane Technologies: Federal Research and Adoption Issues

Summary
In the United States, desalination and membrane technologies are increasingly used to augment
municipal water supply, to produce high quality industrial water supplies, and to reclaim
contaminated supplies (including from oil and gas development). As of 2005, approximately
2,000 desalination facilities larger than 0.3 million gallons per day (MGD) were operating in the
United States, with a total capacity of 1,600 MGD which represents more than 2.4% of total U.S.
municipal and industrial freshwater use. At issue for Congress is what should be the federal role
in supporting desalination and membrane technology research and facilities. Desalination issues
before the 113th Congress include how to focus federal research, at what level to support
desalination research and projects, and how to provide a regulatory context that protects the
environment and public health without disadvantaging the technology.
Desalination processes generally treat seawater or brackish water to produce a stream of
freshwater, and a separate, saltier stream of water that requires disposal (often called waste
concentrate). In the last decade, many states (e.g., Florida, California, and Texas) and cities have
actively investigated the feasibility of large-scale municipal desalination. Coastal communities
look to seawater or estuarine water, while interior communities look to brackish aquifers. The
most common desalination technology in the United States is reverse osmosis, which uses
permeable membranes to separate the freshwater from the saline water supply. Membrane
technologies are also effective for other water treatment applications. Many communities and
industries use membranes to remove contaminants from drinking water, treat contaminated water
for disposal, and reuse industrial wastewater (e.g., saline waters co-produced from oil and gas
development). For some applications, there are few competitive technological substitutes.
Wider adoption of desalination is constrained by financial, environmental, and regulatory issues.
Although desalination costs dropped steadily in recent decades, significant further decline may
not happen with existing technologies. Electricity expenses represent from one-third to one-half
of the operating cost of desalination. Its energy intensity also raises concerns about associated
greenhouse gas emissions and its usefulness as a climate change adaptation measure. Substantial
uncertainty also remains about the technology’s environmental impacts, in particular management
of the saline waste concentrate and the effect of surface water intake facilities on aquatic
organisms. Desalination facilities require a significant number of local, state, and federal
approvals and permits.
Emerging technologies (e.g., forward osmosis, nanocomposite and chlorine resistant membranes)
show promise for reducing desalination costs. Research to support development of emerging
technologies and to reduce desalination’s environmental and social impacts is particularly
relevant to the debate on the future level and nature of federal desalination assistance. The federal
government generally has been involved primarily in desalination research and development
(including for military applications), some demonstration projects, and select full-scale facilities.
For the most part, local governments, sometimes with state-level involvement, are responsible for
planning, testing, building, and operating desalination facilities. Some states, universities, and
private entities also undertake and support desalination research. While interest in desalination
persists among some Members, especially with drought concerns high, efforts to maintain or
expand federal activities and investment are challenged by the domestic fiscal climate and
differing views on federal roles and priorities.

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Desalination and Membrane Technologies: Federal Research and Adoption Issues

Contents
A Primer on Desalination ................................................................................................................. 1
Recent Congressional Consideration ......................................................................................... 2
Federal Desalination Research ......................................................................................................... 3
Research Agenda ....................................................................................................................... 3
Federal Research Funding ......................................................................................................... 5
Desalination Adoption in the United States ..................................................................................... 6
Energy Concerns and Responses ............................................................................................... 7
Reducing Energy Intensity To Reduce Cost Uncertainties.................................................. 7
Emissions Concerns and Renewable Energy Opportunities................................................ 9
Health and Environmental Concerns ......................................................................................... 9
Evolving Drinking Water Guidelines ................................................................................ 10
Concentrate Disposal Challenges and Alternatives ........................................................... 11
Concluding Remarks ..................................................................................................................... 12

Appendixes
Appendix A. Traditional and Emerging Desalination Technologies .............................................. 13

Contacts
Author Contact Information........................................................................................................... 15

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A Primer on Desalination
Interest in desalination technologies for seawater, brackish water, and contaminated freshwater
has increased globally and in the United States, as costs have fallen and pressure to develop
drought-proof water supplies has grown. Adoption of desalination, however, remains constrained
by financial, environmental, regulatory, and social factors. At issue is what role Congress
establishes for the federal government in desalination, particularly in desalination research and
development and the federal regulatory environment related to desalination. Also of congressional
interest is what role desalination may play in meeting future water supply needs. Desalination
processes generally treat seawater, brackish water,1 or impaired waters to produce a stream of
freshwater, and a separate, saltier stream of wastewater, often called waste concentrate or brine.
The availability and regulation of disposal options for the waste concentrate can pose issues for
desalination’s adoption in some locations.
Desalination’s attractions are that it can create a new source of freshwater from otherwise
unusable waters, and that this source may be more dependable and drought-proof than freshwater
sources that rely on annual or multi-year precipitation, runoff, and recharge rates.2 Another
significant application of desalination technologies is for treatment of contaminated waters or
industrial water or wastewater. Some communities and industries use technologies developed for
desalination to produce drinking water that meets federal standards, to treat contaminated water
supplies to meet disposal requirements, or to reuse industrial wastewater (e.g., saline waters co-
produced from oil and gas development). Many of the technologies developed for desalination
also can produce high-quality industrial process water. For many of these applications, there may
be few technological substitutes that are equally as effective and reliable as the desalination
technologies.
There are a number of desalination methods. Two processes, thermal (e.g., distillation) and
membrane (e.g., reverse osmosis), are the most common, with reverse osmosis dominating in the
United States. For more information on the traditional and emerging desalination technologies,
see Appendix A.
Desalination treatment costs have dropped steadily in recent decades, making it more competitive
with other water supply augmentation and treatment options. Electricity expenses vary from one-
third to one-half of the cost of operating desalination facilities.3 A rise in electricity prices could
reverse the declining trend in desalination costs; similarly, drops in electricity costs (e.g., due to
falling costs associated with natural gas-fueled electric generation) improve desalination’s
competitiveness. Costs and cost uncertainties remain among the most significant challenges to
implementing large-scale desalination facilities, especially seawater desalination plants.4

1 For more information on what is brackish groundwater, see National Ground Water Association, Brackish
Groundwater
, NGWA Information brief, Westerville, OH, July 21, 2010, http://www.ngwa.org/Media-Center/briefs/
Documents/Brackish_water_info_brief_2010.pdf.
2 For more on drought, see CRS Report RL34580, Drought in the United States: Causes and Issues for Congress, by
Peter Folger, Betsy A. Cody, and Nicole T. Carter.
3 S. Chaudry, “Unit cost of desalination,” California Desalination Task Force, California Energy Commission, 2003.
4 A survey of municipal desalination facilities in Texas found the cost for brackish desalination ranged from $410 to
$847 per acre-foot, and for seawater desalination ranged from $1,168 to $1,881 per acre-foot. (J. Arroyo and S. Shirazi,
Cost of Water Desalination in Texas, Texas Water Development Board, Austin, TX, October 2009, p. 6,
http://www.twdb.texas.gov/innovativewater/desal/doc/
(continued...)
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Desalination’s energy intensity also raises concerns about the greenhouse gas emissions emitted
and its usefulness as part of a climate change adaptation strategy.5 Substantial uncertainty also
remains about the environmental impacts of large-scale desalination facilities. Social acceptance
and regulatory processes also affect the technologies’ adoption and perceived risks. Research and
additional full-scale facilities may resolve uncertainties, alleviate concerns, and contribute to cost
reductions and options for mitigating environmental impacts.
To date, the federal government has been involved primarily in research and development, some
demonstration projects, and select full-scale facilities (often through congressionally directed
spending). The federal government also may support construction of municipal desalination
facilities through loans provided to these facilities through the U.S. Environmental Protection
Agency’s (EPA’s) Drinking Water State Revolving Loan Funds. For most municipal desalination
facilities, local governments or public water utilities, sometimes with state-level involvement and
federal construction loans, have been responsible for planning, testing, building, and operating
desalination facilities, similar to their responsibility for treating freshwater drinking water
supplies. During recent Congresses, legislative proposals have identified a range of different
potential federal roles in desalination. The most recent fiscal years have seen a decline in federal
support for desalination research and desalination facilities.
Recent Congressional Consideration
Desalination issues before the 113th Congress include how to focus federal research to produce
results that provide public benefits, at what level to support desalination research and projects,
and how to provide a regulatory context that protects the environment and public health without
unnecessarily disadvantaging these technologies. In a provision in the Consolidated
Appropriations Act of 2012 (§204 of Division B of P.L. 112-74), the 112th Congress extended
through 2013 the Water Desalination Act, which authorizes appropriations for the main
desalination research and demonstration outreach program of the Department of the Interior
program which is carried out by the Bureau of Reclamation. The extension was for an annual
authorized level of $3 million. The act also appropriated $2 million for the program in FY2012;
the President had requested $2 million. Authorization of the program beyond 2013 was the
subject of a House Natural Resources Water and Power Subcommittee hearing in April 17, 2012,
and was the subject of H.R. 2664 (112th Congress), Reauthorization of Water Desalination Act of
2011. The bill as introduced (which was prior to the extension in P.L. 112-74) would reauthorize
the program for $2 million annually for FY2012 to FY2016. The April 2012 hearing illustrated
the range of opinions on the federal role in desalination research, with one witness arguing
against further federal support for this type of a research6 while other witnesses discussed
research areas warranting the federal program’s extension.7

(...continued)
Cost_of_Desalination_in_Texas.pdfhttp://www.twdb.state.tx.us/iwt/desal/docs/Cost_of_Desalinati
on_in_Texas.pdf.) Water produced from proposed seawater desalination facilities in California is estimated to
range from $1,900 to $3,000 per acre-foot (H. Cooley and N. Ajami, Key Issues for Desalination in California: Cost
and Financing
, Pacific Institute, November 2012, p. 5, http://www.pacinst.org/reports/desalination_2013/
financing_final_report.pdf).
5 J. McEvoy and M. Wilder, “Discourse and desalination: Potential impacts of proposed climate change adaptation
interventions in the Arizona-Sonora border region,” Global Environmental Change, vol. 22 (2012).
6 U.S. Congress, House Committee on Natural Resources, Subcommittee on Water and Power, Testimony of Wayne
(continued...)
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Congress in recent years also supported the Department of the Interior’s construction of the
Brackish Groundwater National Desalination Research Facility.8 A provision in S. 1343 (112th
Congress), the Energy and Water Integration Act of 2011, would have directed the Secretary of
the Interior to operate, maintain, and manage the facility and authorize appropriations of $2
million annually through 2016. The provision also would have directed that the facility conduct
research, development, and demonstration activities to promote brackish groundwater
desalination, including the integration of desalination and renewable energy technologies, and
outreach programs with public and private entities and for public education. The facility’s mission
also includes managing the waste concentrated from desalination, desalinating waters produced
during oil and gas production, and small-scale desalination systems.
H.R. 5826 (112th Congress), the Coordinating Water Research for a Clean Water Future Act of
2012, would have formally established a National Water Research and Development Initiative
through the National Science and Technology Council (NSTC). The council would have been
required to develop, within a year of enactment, and updated every three years thereafter, a five-
year plan to guide federal water research aimed at enhancing reliable and clean water supply
systems. Although the bill did not specifically list desalination or membranes, the scope of the
initiative appeared to include these treatment technologies.
Federal Desalination Research
Research Agenda
Several reports in the last decade have aimed to inform the path forward for U.S. desalination
research. The first was the 2003 Desalination and Water Purification Technology Roadmap
produced by the Bureau of Reclamation and Sandia National Laboratories at the request of
Congress. The National Research Council reviewed the roadmap in a 2004 report, Review of the
Desalination and Water Purification Technology Roadmap
, which called for a strategic national
research agenda. To this end, the National Research Council convened a Committee on
Advancing Desalination Technology. That NRC committee published a report in 2008,
Desalination: A National Perspective. It concluded that research should focus on reducing the
cost of desalination and that substantial further cost savings are unlikely to be achieved through
incremental advances in the commonly used desalination technologies, like reverse osmosis.
Consequently, the report recommended that federal desalination research funding be targeted at
long-term, high-risk research not likely to be attempted by the private sector that could

(...continued)
Crews, Competitive Enterprise Institute, Hearing on H.R. 2664, 112th Cong., 2nd sess., April 17, 2012,
http://naturalresources.house.gov/UploadedFiles/CrewsTestimony04.17.12.pdf.
7 U.S. Congress, House Committee on Natural Resources, Subcommittee on Water and Power, Testimony of Ian C.
Watson, American Membrane Technology Association
, Hearing on H.R. 2664, 112th Cong., 2nd sess., April 17, 2012,
http://naturalresources.house.gov/UploadedFiles/WatsonTestimony04.17.12.pdf; and Testimony of David Murillo,
Bureau of Reclamation,
,http://naturalresources.house.gov/UploadedFiles/MurilloTestimony04.17.12.pdf.
8 The Brackish Groundwater National Desalination Research Facility is a federally constructed research facility focused
on developing desalination technologies for brackish and impaired groundwater found in inland states. It is located in
Alamogordo, Otero County, NM. The facility opened in August 2007 and is integrated into Department of the Interior’s
existing desalination research and development program at the Bureau of Reclamation. It brings together researchers
from other federal agencies, universities, the private sector, research organizations, and state and local agencies.
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significantly reduce desalination costs. It also recommended a line of research on minimizing or
mitigating the desalination’s environmental impacts of desalination. NRC specifically identified
research relevant for federal investment because of its benefits being widespread and little
willingness to undertake the research by the private sector. (See “National Research Council 2008
Desalination Research Recommendations” box for more details on the research recommendations
in the report.)

National Research Council 2008 Desalination Research Recommendations

The NRC in 2008 identified topics for a research agenda of interest both for public and private sector investment.
The topics considered by NRC to be the most appropriate for the federal support are identified below in italics.
The NRC recommended steps to reduce the financial cost of desalination with research to

Improve pretreatment for membrane desalination

Improve membrane system performance

Develop improved energy recovery technologies and techniques

Reduce existing desalination approaches’ primary energy use by integrating desalination and renewable energy,
understanding energy pricing impacts, and identifying opportunities to use low-grade and waste heat.

Develop novel desalination processes or approaches that reduce primary energy use
The NRC identified the fol owing priority research areas to address environmental concerns:

Assess environmental impacts of desalination intake and concentrate management approaches, and synthesize
results in a national assessment;

Improve intake methods at coastal facilities to minimize harm to organisms;

Develop cost-effective approaches for concentrate management that minimizes environmental impacts; and

Develop monitoring and assessment protocols for evaluating the potential ecological impacts of surface water
concentrate discharge.
Additionally the NRC identified the fol owing cross-cutting research activities:

Develop cost-effective concentrate management that minimizes environmental impacts
Source: NRC, Desalination: A National Perspective, 2008.

In 2010, the Water Research Foundation, WateReuse Foundation, and Sandia National
Laboratories published a report on how to implement the 2003 roadmap.9 The report identifies
research agendas for a range of topics—membrane technologies, alternative technologies,
concentrate management, and institutional issues such as energy cost reduction and regulatory
compliance.

9 Water Research Foundation, WateReuse Foundation, Sandia National Laboratories, Implementation of the National
Desalination and Water Purification Technology Roadmap
, January 2010, http://www.sandia.gov/water/docs/
DesalImplementRoadmap1-26-2010_c_web.pdf.
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Federal Research Funding
No one federal agency has responsibility for all federal desalination and membrane research;
instead numerous agencies and departments are involved in promoting related research based on
their specific missions. In FY2005, FY2006, and FY2007, federal desalination research totaled
$24 million, $24 million, and $10 million, respectively.10 (These are the most recent
comprehensive data on federal desalination funding.) The Bureau of Reclamation was responsible
for half or less of that spending at $12 million, $11 million, and $4 million, respectively. Other
agencies and departments with spending on desalination research included the Army, National
Science Foundation, Office of Naval Research, U.S. Geological Survey, and four of the
Department of Energy’s National Laboratories. Sandia National Laboratory has had the largest
role among the national laboratories. In FY2005 and FY2006, much of the federal desalination
research was congressionally directed to specific sites and activities. The level of funding fell
after FY2006, when the appropriations process began to include less congressionally directed
spending.
The optimal level and type of federal support for desalination research is inherently a public
policy question shaped by factors such as fiscal priorities and views on the appropriate role of the
federal government in research, industry development, and water supply.11 Federal support for
desalination research raises questions, such as what should be the respective roles of federal
agencies, academic institutions, and the private sector in conducting research and
commercializing the results, and should federal research be focused on basic research or
promoting the use of available technologies? In addition to federal and private research activities,
some states, such as California and Texas, also have supported desalination research.12
In 2008, the National Research Council recommended a federal desalination research level of
roughly $25 million, but recommended that the research be targeted strategically, including being
directed at the research activities described above.13 The NRC drew the following conclusion:
There is no integrated and strategic direction to the federal desalination research and development
efforts. Continuation of a federal program of research dominated by congressional earmarks and
beset by competition between funding for research and funding for construction will not serve the

10 National Research Council, Desalination: A National Perspective, 2008, p. 228. Hereafter referred to as NRC 2008.
11 For more information on the general discourse about federal funding for research and development, see CRS Report
R42410, Federal Research and Development Funding: FY2013, coordinated by John F. Sargent Jr. Part of the debate
about the level of desalination research to support in the United States is related to how much desalination research is
occurring outside of the United States. While the U.S. research previously was significant in the development of
desalination especially membrane desalination, the United States now is less prolific than other nations. For example,
In a 2011 article analyzing the research institutes producing journal articles on desalination, no U.S. entity was in the
top 10; the leading institutes in terms of publications were in Australia (1), China (3), India (1), Jordan (1), Kuwait (2),
Oman (1), Poland (1), and Singapore (1) (H. Tanaka and Y. Ho, “Global trends and performance of desalination
research,” Desalination and Water Treatment, vol. 25 (January 2011). Whether this shift signals a reason for more
support for U.S. desalination research or for less since other nations are investing depends on one’s views on research
to support industry and whether the internationally conducted research is meeting U.S. needs.
12 For example in 2003, House Bill 1370 of the 78th Texas Legislature directed the Texas Water Development Board to
participate in research, studies, investigations and surveys to further the development of cost-effective water supplies
from seawater desalination. As of May 2012, the Board has spent $4.2 million on 18 brackish and seawater desalination
demonstration projects and related activities since 2004.
13 NRC 2008. According to the 2004 NRC report, Confronting the Nation’s Water Problems: The Role of Research, in
the past the federal government invested more in this area; in the late 1960s, federal research in desalination and other
saline water conversion activities exceeded $100 million annually.
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nation well and will require the expenditure of more funds than necessary to achieve specified
goals.14
The Bureau of Reclamation’s desalination and membrane research spending has declined since
FY2005 and FY2006. It ranged from $3.7 million and $4.0 million between FY2009 and
FY2011; for FY2012, the bureau received $2.0 million for this work, and the Administration
requested $3.0 million for FY2013.
In the 2008 NRC report, the Office of Naval Research followed the Bureau of Reclamation in
spending on desalination research. In FY2010, FY2011, and FY2012, desalination research by the
office was funded at $2.6 million, $4.4 million, and $5.3 million, respectively.15 The
Administration requested $4.5 million for FY2013 and shifted the research to a new program,
Future Naval Capabilities.16
While some of the traditional avenues for federal desalination research are receiving less support,
some new avenues may be opening. Two of these are the Advanced Research Projects Agency-
Energy (ARPA-E) and the National Science Foundation’s Urban Water Engineering Research
Center that was initiated in 2011.
Desalination Adoption in the United States
Desalination and membrane technologies are increasingly investigated and used as an option for
meeting municipal and industrial water supply and water treatment demands. The nation’s
installed desalination capacity has increased in recent years, reflecting the technology’s growing
competitiveness and applications and increasing demands for reliable freshwater supplies. As of
2005, approximately 2,000 desalination plants larger than 0.3 million gallons per day (MGD)
were operating in the United States, with a total capacity of 1,600 MGD.17 This represents more
than 2.4% of total U.S. municipal and industrial freshwater withdrawals, not including water for
thermoelectric power plants.
Florida, California, Texas, and Arizona have the greatest installed desalination capacity. Florida
dominates the U.S. capacity, with the facility in Tampa being a prime example of large-scale
desalination implementation (see box); however, Texas and California are bringing plants online
or are in advanced planning stages. Several other efforts also are preliminarily investigating
desalination for particular communities, such as Albuquerque. Two-thirds of the U.S. desalination
capacity is used for municipal water supply; industry uses about 18% of the total capacity.18
The saline source water that is treated using desalination technologies varies largely on what
sources are available near the municipalities and industry with the demand for the water. In the
United States, only 7% of the existing desalination capacity uses seawater as its source. More
than half of U.S. desalinated water is from brackish sources. Another 25% is river water treated

14 NRC 2008.
15 Personal communication with CRS by email from Navy Office of Legislative Affairs, June 8, 2012.
16 Ibid.
17 H. Cooley et al., Desalination, With a Grain of Salt: A California Perspective, Pacific Institute (June 2006).
18 Ibid.
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for use in industrial facilities, power plants, and some commercial applications. Globally,
seawater desalination represents 60% of the installed desalination capacity.19
While interest in obtaining municipal water from desalination is rising in the United States,
desalination is expanding most rapidly in other world regions, often in places where other supply
augmentation options are limited by geopolitical as well as natural conditions, such as arid
conditions with access to seawater. The Middle East, Algeria, Spain, and Australia are leading in
the installation of new desalination capacity,20 with Saudi Arabia and the United Arab Emirates
leading in annual production of desalinated water.

Tampa’s and San Diego’s Desalination Experiences and Lessons
Tampa’s planning of the first large-scale (25 MGD) desalination plant in the late 1990s ignited interest in large-scale
desalination as a municipal water supply source elsewhere in the United States. The facility was thought of as a signal
of desalination becoming a cost-effective supply option, However, the Tampa plant, a facility to desalinate heavily
brackish estuarine water, encountered technical and economic problems (e.g., less freshwater produced than
anticipated, fouling of reverse osmosis membranes, financing issues) during construction and start-up, driving up the
cost of the freshwater produced. For some observers, a lesson from the Tampa plant experience is one of caution;
before proceeding to full-scale implementation, large-scale desalination requires careful investigation. In the view of
industry observers, the lessons to be learned from Tampa are that (1) good design suited to the local conditions and
(2) a thorough pilot-study are critical for a desalination facility to function properly. For other observers, the Tampa
project illustrates some of the risks of working with private water developers and lowest-bid contracts without
sufficient external review and accountability mechanisms. Private developers, however, remain attractive for some
communities because of their role in financing the capital cost of constructing a large-scale desalination facility.
In 1998, just north of San Diego in Carlsbad, California, a private joint venture, Poseidon, initiated its effort to build a
50 MGD seawater desalination facility to sel water to San Diego’s water system, In November 2009, Poseidon
received al of the permits for the Carlsbad project. In November 2012, the San Diego County Water Authority
approved the purchase of the desalinated water for thirty years. The project costs in 2012 were estimated at close to
$1billion, which represents a significant increase from estimates a decade earlier at $270 million; the cost for
delivered desalinated water from the plant is estimated at $1,600 per acre-foot. The plant is expected to complete
construction and begin water deliveries in 2016. The extended negotiation and approval process illustrated some of
the tensions and concerns that arise during private-sector engagement in provision of municipal water. While
Poseidon owned a prime location site for a desalination facility, the water authority and public were hesitant about
the arrangement because of concern over profit-taking by a private entity engaged in the provision of a public service.
After more than a decade, this concern and other concerns (e.g., environmental impacts) were overcome and
mitigated. The Poseidon Carlsbad experience has yielded lessons about the public’s expectations for transparency and
protections when the private sector is involved in desalination or other aspects of public services and infrastructure.
Desalinations stakeholders are anticipated to continue to watch the Poseidon Carlsbad facility and arrangement for
lessons and precedents as implementation proceeds.

Energy Concerns and Responses
Reducing Energy Intensity To Reduce Cost Uncertainties
The cost of desalination for municipal water remains a barrier to adoption. Like nearly all new
freshwater sources, desalinated water comes at substantially higher costs than existing municipal
water sources.

19 Ibid.
20 J. Hughes, “Seawater Desalination Leads Response to Global Water Crisis,” AWWA Streamlines, Nov. 10, 2009.
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Much of the cost for seawater desalination is for the energy required for operations; in particular,
the competitiveness of reverse osmosis seawater desalination is highly dependent on the price of
electricity. Reverse osmosis pushes water through a membrane to separate the freshwater from the
salts; this requires considerable energy input. Currently the typical energy intensity for seawater
desalination with energy recovery devices is 3-7 kilowatt-hours of electricity per cubic meter of
water (kWh/m3).21 The typical energy intensity of brackish desalination is less than seawater
desalination, at 0.5-3 kWh/m3, because the energy required for desalination is a function of the
salinity of the source water.22
Uncertainty in whether electricity prices will rise or fall creates significant uncertainty in the cost
of desalinated water. If electricity becomes more expensive, less electricity-intensive water
supply options (which may include conservation, water purchases, and changes in water pricing)
become comparatively more attractive. Recent drops in natural gas prices and little to no growth
in electricity demand has increased the cost competitiveness of existing desalination technologies
in recent years.
Cost-effectively reducing desalination’s energy requirements could help reduce overall costs. In
recent decades, one of the ways that desalination cost reductions were achieved was through
reduced energy requirements of reverse osmosis processes. Now the energy used in the reverse
osmosis portion of new desalination facilities is close to the theoretical minimum energy required
for separation of the salts from the water.23 Therefore, although there still is some room for energy
efficiency improvements in using desalination as a water supply, dramatic improvements are not
likely to be achieved through enhancements to standard reverse osmosis membranes. Instead
energy efficiency improvements are more likely to come from other components of desalination
facilities, such as the pretreatment24 of the water before it enters the reverse osmosis process,
enhanced facility and system design, or the use and development of a new generation of
technologies (see Appendix A).
For example, energy efficiency advances in the non-membrane portions of water systems and the
use of energy recovery technologies are reducing energy use per unit of freshwater produced at
desalination facilities. Pumps are responsible for more than 40% of total energy costs at a
desalination facility.25 Energy efficiency advances in a type of pump that is useful for smaller
applications (called a positive displacement pump) have made desalination more cost-effective
for some applications and locations and less sensitive to electricity price increases.26

21 NRC 2008, pp. 74-75, and 77.
22 Ibid., p. 77.
23 M. Elimelech and W.A. Phillip, “The Future of Seawater Desalination: Energy, Technology, and the Environment,”
Science, vol. 333 (August 5, 2011), pp. 712-717.
24 Pretreatment is necessary in order to avoid fouling and harm to the reverse osmosis membranes.
25 A. Subramani, “Energy minimization strategies and renewable energy utilization for desalination: a review,” Water
Research
, vol. 45, no. 5 (February 2011), pp. 1907-1920.
26 A. Bennett, “Innovation continues to lower desalination costs,” Filtration+Separation, July/August 2011. Packaging
of pre-engineered membrane-based desalination plants also have reduced the upfront capital costs for some desalination
applications.
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Emissions Concerns and Renewable Energy Opportunities
Desalination’s electricity consumption has greenhouse gas and other emissions associated with it
if the electricity is generated using fossil fuels. The use of desalination as a climate change
adaptation strategy is questioned because of its potential fossil fuel intensity relative to other
adaptation and water supply options.27 Electricity price uncertainty and emissions considerations
have driven many desalination proponents to investigate renewable energy supplies and co-
location with power plants.28
The extent to which desalination technologies can be coupled with intermittent renewable or
geothermal electric generation,29 use off-peak electricity, and operate in areas of limited electric
generation or transmission capacity but with renewable energy resources is increasingly receiving
attention. Desalinating more water when wind energy is available (which requires facilities that
can operate with a variable water inflow) and storing the treated water for when water is
demanded can almost be viewed as a means of electricity storage and reduction of peak
demand.30 Efforts to jointly manage water and energy supply and demand and to integrate
renewable energy with desalination may bolster support for desalination.
Health and Environmental Concerns
From a regulatory, oversight, and monitoring standpoint, desalination as a significant source of
water supply is new in the United States, which means the health and environmental regulations,
guidelines, and policies regarding its use are still being developed. Existing federal, state, and
local laws and policies often do not address unique issues raised by desalination. This creates
uncertainty for those considering adopting desalination and membrane technologies.
Environmental and human health concerns often are raised in the context of obtaining the permits
required to site, construct, and operate the facility and dispose of the waste concentrate. A draft
environmental scoping study for a facility in Brownsville, TX, identified up to 26 permits,
approvals, and documentation requirements for construction and operation of a seawater
desalination facility.31 According to the Pacific Institute’s report Desalination, With a Grain of
Salt
, as many as 9 federal, 13 state, and additional local agencies may be involved in the review
or approval of a desalination plant in California. For example, during the Corps’ process for
issuing a seawater desalination facility permits for placing structures in waterways and dredging
and filling in navigable waters, the U.S. Coast Guard would consult with the Army Corps of
Engineers on whether an intake facility would be a potential navigation hazard and the National

27 J. McEvoy and M. Wilder (2012).
28 A major benefit of co-location is using the cooling water from the power plant for desalination; this water has been
warmed by the power plant which reduces the energy requirements for desalinating it. Also, the desalination facility
may avoid construction costs by sharing intake and discharge facilities.
29 Ibid.
30 For example, M.S. Miranda and D. Infield, “A wind-powered seawater reverse-osmosis system without batteries,”
Desalination, vol. 153 (2002); D. Weiner et al., “Operation experience of a solar- and wind-powered desalination
demonstration plant,” Desalination, vol. 137 (2001).
31 Texas Water Development Board, The Future of Desalination in Texas: 2010 Biennial Report, Austin, TX,
Dec.2010, p. 8, http://www.twdb.state.tx.us/innovativewater/desal/doc/2010_TheFutureofDesalinationinTexas.pdf. The
report includes a table listing the permits, approvals, and environmental documentation compliance requirements, and
estimates of the cost for obtaining each. To reduce the time and expense of the project development process, the Board
has supported a study to develop a permitting and decision model for desalination projects in Texas.
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Oceanic and Atmospheric Administration would consult on whether intake facilities and
discharge of waste concentrate may affect marine resources. Some of the regulatory hurdles are
not particularly onerous; others may be particularly challenging depending on the location and
size of the facility. In California in 2012, Assembly Bill 2595 was introduced; it would require
California’s Ocean Protection Council to create a task force to study how to streamline the state
permitting process for seawater desalination facilities. No similar legislation for the federal
process has been proposed during the 112th Congress.
Some stakeholders view the current permit process as a barrier to adoption of desalination. Other
stakeholders argue that rigorous permitting is necessary because of the potential impact of the
facilities on public health and the environment. Particular attention is often paid to the
impingement and entrainment of aquatic species by intake structures of coastal and estuarine
facilities and the disposal of waste concentrate.
Evolving Drinking Water Guidelines
While the quality of desalinated water is typically very high, some health concerns remain
regarding its use as a drinking water supply. The source water used in desalination may introduce
biological and chemical contaminants to drinking water supplies that are hazardous to human
health, or desalination may remove minerals essential for human health.
For example, boron, which is an uncommon concern for traditional water sources, is a significant
constituent of seawater and can also be present in brackish groundwater extracted from aquifers
comprised of marine deposits. Boron levels after basic reverse osmosis of seawater commonly
exceed current World Health Organization health guidelines and the U.S. Environmental
Protection Agency (EPA) health reference level.32 While the effect of boron on humans remains
under investigation, boron is known to cause reproductive and developmental toxicity in animals
and irritation of the digestive tract, and it accumulates in plants, which may be a concern for
agricultural applications.33 Boron can be removed through treatment optimization, but that
treatment could increase the cost of desalted seawater.
EPA sets federal standards and treatment requirements for public water supplies.34 In 2008, EPA
determined that it would not develop a maximum contaminant level for boron because of its rare
occurrence in most groundwater and surface water drinking water sources; EPA has encouraged
affected states to issue guidance or regulations as appropriate.35 Most states have not issued such

32 The EPA Longer Term Health Advisory level for boron is 2.0 milligram-per-liter (mg/L). Boron occurs in oceans at
an average concentration of 4.5 mg/L. Concentrations in water derived from basic reverse osmosis of seawater often
are near but necessarily below the EPA Advisory level (NRC 2008). A second pass through reverse osmosis membrane
with a pH adjustment can effectively remove the boron; boron removal increases with pH. Some states have drinking
water standards or guidelines for boron (California, Florida, Maine, Minnesota, New Hampshire and Wisconsin); these
range from 0.6 to 1 mg/L. (USEPA, Summary Document form the Heath Advisory for Boron and Compounds, Doc. No.
822-S-08-003, 2008.)
33 According to the NRC 2008, while boron is recognized to have a beneficial role in some physiological processes in
some species, higher exposure levels may cause adverse human health effects. EPA has concluded there is inadequate
data to assess the human carcinogenicity of boron. Most of the boron toxicity data come from studies in laboratory
animals.
34 For more information on EPA’s role in protecting drinking water, see CRS Report RL31243, Safe Drinking Water
Act (SDWA): A Summary of the Act and Its Major Requirements
, by Mary Tiemann.
35 EPA, Regulatory Determinations for Priority Contaminant s on the Second Drinking Water Contaminant Candidate
List, available at http://www.epa.gov/OGWDW/ccl/reg_determine2.html.
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guidance. Therefore, most U.S. utilities lack clear guidance on boron levels in drinking water
suitable for protecting public health. The National Research Council recommended development
of boron drinking water guidance to support desalination regulatory and operating decisions; it
recommended that the guidance be based on an analysis of the human health effects of boron in
drinking water and other sources of exposure.
Similarly, the demineralization (particularly the removal of the essential minerals calcium and
magnesium) by desalination processes also can raise health concerns.36 This has prompted
researchers to promote the remineralization of desalinated water prior to the water entering the
distribution system in communities that are highly dependent on desalinated water.37 Another
health-related concern is the extent to which microorganisms unique to seawater and algal toxins
may pass through reverse osmosis membranes and enter the water supply, and how facilities may
need to be operated differently when these organisms and algal toxins are present. Algal toxins
are a consideration for desalination facilities in locations affected or potentially affected by
harmful ocean algal blooms that can produce a range of substances ranging from noxic to
neurotoxic (e.g., domoic acid). How to effectively manage desalination facilities in order to avoid
public health treats from algal blooms is an emerging area of interest and research.38
Some of the coastal facilities contemplated in the United States would treat estuarine water.
Estuarine water, which is a brackish mixture of seawater and surface water, has the advantage of
lower salinity than seawater. The variability in the quality and constituents in estuarine water, as
well as the typical surface water contaminants (e.g., infectious microorganisms, elevated nutrient
levels, and pesticides), may complicate compliance of desalinated estuarine water with federal
drinking water standards.
Concentrate Disposal Challenges and Alternatives
For inland brackish desalination, significant constraints on adoption of the technologies are the
uncertainties and the cost of waste concentrate disposal. For coastal desalination projects, the
concentrate management options are often greater because of surface water disposal
opportunities. EPA is authorized to manage the disposal and reuse of desalination’s waste
concentrate.39 The disposal option selected largely is determined by which alternatives are

36 Fluoride is low in seawater and is further depleted by desalination; communities can choose to add fluoride to treated
water consistent with their health goals.
37 J. Cotruvo, “Health Aspects of Calcium and Magnesium in Drinking Water,” Water Conditioning and Purification,
June 2006. Remineralization would also help reduce the corrosivity of desalinated water on piping.
38 According to a 2009 article, “there are no published reports on the effectiveness of reverse osmosis for removing
dissolved algal toxins from seawater. Some of these toxin molecules (e.g., domonic acid) are near the theoretical
molecular size of molecules rejected by reverse osmosis membranes, but experimental studies are required to validate
the effective (sic) of this process on toxin removal” ( D.A. Caron et al., “Harmful algae and their potential impacts on
desalination operations off southern California,” Water Research, (2009). Coastal algal blooms known as red tides were
the subject of a 2012 expert workshop ( “Red Tide and HABs: Impact on Desalination Plants,” Expert Workshop,
Muscat, Sultanate of Oman, Feb. 2012, http://www.medrc.org/index.cfm?area=about&page=
expert_workshop_download.
39 EPA’s authority is derived primarily from the Safe Drinking Water Act and the Clean Water Act. For a CRS report
on the Safe Drinking Water Act, see CRS Report RL31243, Safe Drinking Water Act (SDWA): A Summary of the Act
and Its Major Requirements
, by Mary Tiemann. The sections of the act most significant to disposal of waste
concentrate create the underground injection control (UIC) program; this is in Part C, Protection of Underground
Sources of Drinking Water, §§1421-1426 (42 U.S.C. §§300h-300h-5). The Clean Water Act establishes the federal
standards for surface water disposal and requirements for obtaining permits for these discharges. For more on the Clean
(continued...)
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appropriate for the specific characteristics of the concentrate and the cost-effectiveness of the
alternatives, which is largely shaped by the proximity of the disposal option and the
infrastructure, land, and treatment investments required. Disposal options typically include land
application, evaporative ponds, surface water disposal, or deep well injection.
Land application can include spraying concentrate on salt-tolerant plants or infiltration; land
application typically is used for small volumes of brackish water concentrate. Evaporation ponds
use solar radiation to precipitate salt crystals, which are then harvested and typically disposed; in
some cases the salts or other constituents may be beneficially reused. Surface water disposal of
waste concentrate is permitted on a project-specific basis based on predicted acute and chronic
effects on the environment.40 Inland surface water disposal is particularly challenging because of
the limited capacity of inland water bodies to be able to tolerate the concentrate’s salinity. In
some cases a limited amount of concentrate can be sent to a large-volume wastewater treatment
facility. For injection purposes, EPA generally classifies waste concentrate as an industrial waste,
thus requiring that the concentrate be disposed of in deep wells appropriate for industrial waste.
Desalination proponents argue that desalination’s concentrate is sufficiently different from most
industrial waste that it should be reclassified to increase the surface and injection well disposal
opportunities. Some states (e.g., Texas) have made efforts to promote the beneficial use of waste
concentrate (e.g., use as liquids in enhanced oil and gas recovery) and facilitate its disposal
including land application techniques.41 While states can have such policies and programs in
place, federal environmental regulations administered by EPA for the most part define the
regulatory context of concentrate disposal.
Concluding Remarks
Desalination and membrane technologies are playing a growing role in meeting water supply and
water treatment needs for municipalities and industry. The extent to which this role further
expands depends in part on the cost-effectiveness of these technologies and their alternatives.
Desalination’s energy use, concentrate disposal options, and environmental and health concerns
are among the top issues shaping the technology’s adoption. How to focus federal research to
produce results that provides public benefits, at what level to support it, and how to provide a
regulatory context that protects the environment and public health without unnecessarily
disadvantaging these technologies are the three most significant desalination issues before the
113th Congress.

(...continued)
Water Act, see CRS Report RL30030, Clean Water Act: A Summary of the Law, by Claudia Copeland.
40 N. Voutchkov, Management of Desalination Plant Concentrate, SunCam, 2011, http://s3.amazonaws.com/suncam/
npdocs/113.pdf.
41 For example,, House Bill 2654 passed by the 80th Texas Legislature provided for a general permit for Class I
injection wells that can be used to dispose of brine concentrate from a municipal desalination plant. Also, the Texas
Water Development Board undertook a study with the intent of showing that oil and gas fields can physically and
chemically accept desalination waste concentrate and to recommend changes to statutes and rules to facilitate waste
concentrate disposal in oil and gas fields (R. E. Mace et al., Please Pass the Salt: Using Oil Fields for the Disposal of
Concentrate from Desalination Plants
, Texas Water Development Board, Austin, TX, April 2006,
http://www.twdb.state.tx.us/publications/reports/numbered_reports/doc/Report366.pdf). Since publication of that
report, more questions have arisen related to induced seismic activity from deep well injection; these concerns may
affect how the risks and attractiveness of concentrate brine injection as a disposal method among some stakeholders.
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Appendix A. Traditional and Emerging Desalination
Technologies

There are a number of methods for removing salts from seawater or brackish groundwater to
provide water for municipal and agricultural purposes. The two most common processes, thermal
distillation and reverse osmosis, are described below; their descriptions are followed by
descriptions of some of the more innovative and alternative desalination technologies. The
earliest commercial plants used thermal techniques. Improvements in membrane technology have
reduced costs, and membrane technology is less energy-intense than thermal desalination
(although it is more energy-intense than most other water supply options). Reverse osmosis and
other membrane systems account for nearly 96% of the total U.S. desalination capacity and 100%
of the municipal desalination capacity.
Reverse Osmosis
Reverse osmosis forces salty water through a semipermeable membrane that traps salt on one side
and lets purified water through. Reverse osmosis plants have fewer problems with corrosion and
usually have lower energy requirements than thermal processes.
Examples of how research advances in the traditional desalination technologies of reverse
osmosis have the potential for improving the competitiveness and use of desalination are:
nanocomposite and nanotube membranes and chlorine resistant membranes. Nanocomposite
membranes appear to have the potential to reduce energy use within the reverse osmosis process
by 20%, and nanotube membranes may yield a 30%-50% energy savings.42
Membranes are susceptible to fouling by biological growth (i.e., biofouling), which reduces the
performance of the membranes and increases energy use. The most widely used biocide is
chlorine because it is inexpensive and highly effective. The most common membranes used in
reverse osmosis, however, do not hold up well to exposure to oxidizing agents like chlorine.
Advancements in chlorine resistant membranes would increase the resiliency of membranes and
expand their applications and operational flexibility.43
Distillation
In distillation, saline water is heated, separating out dissolved minerals, and the purified vapor is
condensed. There are three prominent ways to perform distillation: multi-stage flash, multiple-
effect distillation, and solar distillation. In general, distillation plants require less maintenance and
pretreatment before the desalination process than reverse osmosis facilities.
While solar distillation is an ancient means for separating freshwater from salt using solar energy,
research into improving the technology is increasing.44 In large part the interest stems from the

42 A. Subramani (2011).
43 H,B. Park et al., “Highly Chlorine-Tolerant Polymers for Desalination,” Angewandte Chemie, vol. 120 (July 2008),
pp. 6108-6113.
44 H. Tanaka and Y. Ho, “Global trends and performance of desalination research,” Desalination and Water Treatment,
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potential application for the technology to supply freshwater to small remote settlements where
saline supplies are the only source and power is scarce or expensive.
Innovative and Alternative Desalination Processes
Capacitive Deionization
Capacitive deionization desalinates saline waters by absorbing salts out of the water using
electrically charged porous electrodes. The technology uses the fact that salts are ionic
compounds with opposite charges to separate the salts from the water. The limiting factor for this
technology is often the salt absorption capacity of the electrodes. The technology shows promise
for energy-efficient desalination using electrodes of optimized pore size.
Electrodialysis
Electrodialysis and capacitive deionization technologies depend on the ability of electrically
charged ions in saline water to migrate to positive or negative poles in an electrolytic cell. Two
different types of ion-selective membranes are used—one that allows passage of positive ions and
one that allows negative ions to pass between the electrodes of the cell. When an electric current
is applied to drive the ions, fresh water is left between the membranes. The amount of electricity
required for electrodialysis, and therefore its cost, increase with increasing salinity of feed water.
Thus, electrodialysis is less economically competitive for desalting seawater compared to less
saline, brackish water.
Forward Osmosis
Forward osmosis is an increasingly used but relatively new membrane-based separation process
that uses an osmotic pressure difference between a concentrated “draw” solution and the saline
source water; the osmotic pressure drives the water to be treated across a semi-permeable
membrane into the draw solution. The level of salt removal can be competitive with reverse
osmosis. A main challenge is in the selection of a draw solute; the solute needs to either be
desirable in the water supply, or be easily and economically removed. Research is being
conducted on whether a combination of ammonia and carbon dioxide gases can be used as the
draw solution. The attractiveness of forward osmosis is that its energy costs can be significantly
less than for reverse osmosis when combined with industrial or power production processes.45 A
disadvantage of this technology is that it yields a lower quantity of freshwater per unit of water
treated and a larger quantity of brine that requires disposal.46

(...continued)
vol. 25 (Jan. 2011).
45 R. L. McGinnis, and M. Elimelech. “Energy requirements of ammonia carbon dioxide forward osmosis
desalination,” Desalination (2007) 207, pp. 370-382.
46 A. Bennett, “Innovation continues to lower desalination costs,” Filtration+Separation, July/Aug. 2011.
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Freezing Processes
Freezing processes involve three basic steps: (1) partial freezing of the feed water in which ice
crystals of fresh water form an ice-brine slurry; (2) separating the ice crystals from the brine; and
(3) melting the ice. Freezing has some inherent advantages over distillation in that less energy is
required and there is a minimum of corrosion and scale formation problems because of the low
temperatures involved. Freezing processes have the potential to concentrate waste streams to
higher concentration than other processes, and the energy requirements are comparable to reverse
osmosis. While the feasibility of freeze desalination has been demonstrated, further research and
development remains before the technology will be widely available.
Ion Exchange
In ion exchange, resins substitute hydrogen and hydroxide ions for salt ions. For example, cation
exchange resins are commonly used in home water softeners to remove calcium and magnesium
from “hard” water. A number of municipalities use ion exchange for water softening, and
industries requiring extremely pure water commonly use ion exchange resins as a final treatment
following reverse osmosis or electrodialysis. The primary cost associated with ion exchange is in
regenerating or replacing the resins. The higher the concentration of dissolved salts in the water,
the more often the resins need to be renewed. In general, ion exchange is rarely used for salt
removal on a large scale.

Author Contact Information

Nicole T. Carter

Specialist in Natural Resources Policy
ncarter@crs.loc.gov, 7-0854

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