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Summary Efforts to identify new, untapped sources of supply have dominated water policy for the past century. There has been an exponential increase in desalination capacity both globally and nationally since 1960, fueled in part by this growing concern for local water scarcity and made possi- ble to a great extent by a major federal investment for desalination re- search and development in the late 1950s to the early 1980s. Traditional sources of supply are increasingly expensive, unavailable, or controver- sial, but desalination technology offers the potential to substantially re- duce water scarcity by converting the almost inexhaustible supply of seawater and the apparently vast quantities of brackish groundwater into new sources of freshwater. Although total water use in the United States has remained steady over recent decades, interest in brackish water and seawater desalination will likely continue, particularly in water-scarce regions, in localities experiencing rapid population growth, or where us- ers are able and willing to pay for a high-quality, reliable new supply. Historically, the high cost and energy requirements of desalination had confined its use to places where energy is inexpensive and freshwa- ter scarce. Recent advances in technology, especially improvements in membranes, have made desalination a realistic water supply option. The cost of desalinating seawater in the United States is now competitive with other alternatives in some locations and for some high-valued uses, and there is considerable interest in hastening the time when costs of de- salination are routinely competitive with the costs of alternatives. With support from the U.S. Bureau of Reclamation and the U.S. En- vironmental Protection Agency, the National Research Council convened the Committee on Advancing Desalination Technology to assess the state of the art in relevant desalination technologies and factors such as cost and implementation challenges. The committee also was asked to de- scribe reasonable long-term goals for advancing desalination technology and to provide recommendations for action and research. Finally, the committee was asked to estimate the funding necessary to support the 1
2 Desalination: A National Perspective proposed research agenda and to identify appropriate roles for govern- mental and nongovernmental entities. This report builds on a 2004 Na- tional Research Council report that provided a scientific assessment of the Bureau of Reclamationâs and Sandia National Laboratoriesâ Desali- nation and Water Purification Technology Roadmap, or Roadmap, which was intended to serve as a strategic pathway for future desalination and water purification research (USBR and Sandia National Laboratories, 2003). WATER FOR THE FUTURE: THE ROLE OF DESALINATION When considering future water supplies, it is important to recognize that past patterns of water use will not always be a reliable indicator of future demand. In particular, the assumption that water demands will inevitably parallel population and economic growth no longer appears to be correct. Nevertheless, water scarcity in some regions of the United States will certainly intensify over the coming decades, and no one op- tion or set of options is likely to be sufficient to manage this intensifying scarcity. Desalination, using both brackish and seawater sources, is likely to have a niche in the future water management portfolio of the United States. The committee was specifically asked to address the potential for seawater and brackish water desalination to help meet anticipated water supply needs in the United States. The committee concluded that the po- tential for desalination cannot be definitively determined because it de- pends on a host of complicated and locally variable economic, social, environmental, and political factors. In the complete absence of these factors, the theoretical potential for desalination is effectively unlimited. Large quantities of inland brackish groundwater appear to be available for development; in coastal areas, ocean resources are essentially infinite in comparison to human demands. But, as with most resource questions, the theoretical potential and the practical potential are far different. All water management and planning takes place in the context of economic, social, environmental, and political factors, and these factors are far more important than technological desalination process constraints in limiting the potential for desalination to help meet anticipated water supply needs. As a result, this report addresses key technological issues that may lend themselves to focused research and development efforts, but the report also addresses nontechnical questions that may ultimately prove to be more limiting. The costs of producing desalinated waterâthe cost of removing salts to create freshwaterâis no longer the primary barrier to implementing
Summary 3 desalination technology, because there have been significant reductions in desalination production costs. Meanwhile, the costs of other alterna- tives for augmenting water supplies have continued to rise, often making desalination more attractive in a relative sense. A continuation of these trends would likely make desalination costs more attractive and less of a constraint in the future. Nevertheless, concentrate management costs vary widely, depending on local regulations and site-specific conditions, and have generally increased in recent decades. Where low-cost concen- trate management alternatives are not available, the financial costs of desalination can be prohibitive. There is also considerable uncertainty about the environmental impacts of desalination and, consequently, con- cern over its potential effects. Possible environmental impacts of desali- nation are impingement and entrainment of organisms when seawater is taken in, ecological impacts from disposing of salt concentrates, and in- creased greenhouse gas emissions from increased energy use, among other concerns. Although limited studies to date suggest that the envi- ronmental impacts may be less detrimental than many other types of wa- ter supply, site-specific information necessary to make detailed conclu- sions on environmental impacts is typically lacking. A strategic desalination research and development effort can help make desalination a more attractive water supply option for communities facing water shortages and can enable desalination technology to serve a larger role in addressing the nationâs water demands. The two main goals of this research and development effort should be (1) to understand the environmental impacts of desalination and develop approaches to mini- mize these impacts relative to other water supply alternatives, and (2) to develop approaches to lower the financial costs of desalination so that it is an attractive option relative to other alternatives in locations where traditional sources of water are inadequate. Success of the proposed re- search agenda will depend on coordinated federal leadership and partici- pation by state and local governments, nongovernmental organizations, and the private sector. CURRENT INVESTMENT IN DESALINATION RESEARCH AND DEVELOPMENT Based on the committeeâs survey of federal investment in desalina- tion research and development together with estimates and analyses of state, nongovernmental organizations, and private-sector funding, the committee reached several conclusions (see also Chapter 2) that under- score the need for the development of a national strategic research agenda for desalination:
4 Desalination: A National Perspective â¢ There is no integrated and strategic direction to the federal desalination research and development efforts. Desalination research and development efforts are funded through at least nine federal agencies and laboratories, each with their own research objectives and priorities. The majority of federal desalination research and development funding also comes from congressional earmarks, which limits the ability to de- velop a steady research program. Federal funding for desalination re- search declined from approximately $24 million per year in fiscal years (FYs) 2005 and 2006 to $10 million in FY 2007 (a decline of nearly 60 percent), largely due to an absence of earmarks in FY 2007. â¢ Some states, especially California, have also made sizeable recent investments in desalination research and development. The majority of this funding is being directed toward site- or region-specific problems, with heavy emphasis on pilot and demonstration projects. â¢ The private sector appears to fund the majority of desalina- tion research, with total annual spending estimated to be more than twice that of all other surveyed sources of such funding. Based on the judgment of individuals working in the industry, the private sector allo- cates a smaller fraction of its research portfolio to high-risk desalination research than the federal government. Given the large research invest- ment, however, private-sector funding for high-risk activities is estimated to be roughly equivalent to federal funding for high-risk research. STATE OF DESALINATION TECHNOLOGY The state of desalination technology, including intakes, pretreatment, desalination processes, post-treatment, and concentrate management, is outlined in Chapter 4. Industry has made great strides in reducing energy use for desalination with the commercialization of high-efficiency energy recovery devices and improvements in membrane technology. Reverse osmosis (RO) technology is relatively mature, and current energy use is within a factor of 2 of the theoretical thermodynamic minimum value for separating solutes from water. Thus, RO is the standard by which novel desalination technologies should be assessed when specific energy use is the main consideration. Meanwhile, opportunities exist to further reduce cost and energy use of current technologies by small but economically significant amounts: â¢ In RO desalination, the costs and energy requirements of wa- ter production can be further reduced by mitigating fouling through pretreatment; developing high-permeability, fouling-resistant, high- rejection, oxidant-resistant membranes; and optimizing membrane
Summary 5 module and membrane system design. Operating the RO process at lower hydraulic pressure while maintaining high throughput is the key to reducing the specific energy for membrane-based desalination. To fully utilize the capacity of high-permeability RO membranes and to accom- modate even more permeable RO membranes in the future, it is impera- tive to reduce fouling and concentration polarization effects and to de- velop new module configurations and system designs to avoid or over- come thermodynamic restriction. Fouling can be reduced by a more ro- bust pretreatment and by the development of fouling-resistant mem- branes. Practical and economic constraints, however, are likely to inhibit RO energy use from decreasing more than approximately 15 percent be- low the values of the best current technology. This level of improvement would still be valuable for reducing cost and energy use, but greater re- turns on investment than this should not be expected. â¢ Seawater desalination using thermal processes can be cost ef- fective when waste heat is utilized effectively. Location of low-grade and/or waste heat resources near large water consumers may reduce the cost of heat energy and offset the higher specific-energy requirements of thermal desalination when compared to RO. Hybrid membraneâthermal desalination approaches offer additional operational flexibility and op- portunities for water production cost savings for facilities co-located with power plants. â¢ Few, if any, cost-effective environmentally sustainable con- centrate management options exist for inland desalination facilities. Several methods are currently available for concentrate management, and each method has its own set of site-specific costs, benefits, regulatory requirements, environmental impacts, and limitations. Low- to moderate- cost inland disposal options can be limited by the salinity of the concen- trate and by location and climate factors. Only evaporation ponds and high-recovery/thermal evaporation systems are zero-liquid discharge so- lutions, but high costs limit their consideration for most municipal appli- cations. ENVIRONMENTAL IMPACTS Knowledge of the potential environmental impacts of desalination processes is essential to water supply planners when they consider de- salination among many water supply alternatives. All components of the water use cycle should be considered, including source water impacts, the likely greenhouse gas emissions from the energy requirements of the desalination process, potential impacts from concentrate management approaches, and environmental health considerations in the product wa-
6 Desalination: A National Perspective ter. Ideally, these considerations should be compared against equally rig- orous environmental impact analyses of water supply alternatives, so that decisions can be made based on comparisons of the full economic costs and benefits, including environmental and social costs and benefits, among the various water supply alternatives. There is a considerable amount of uncertainty about the envi- ronmental impacts of desalination and, consequently, concern over its potential effects. Therefore, the following research is recommended: â¢ Site-specific assessments of the impacts of source water with- drawals and concentrate management should be conducted and the results synthesized in a national assessment of potential impacts. The ecological effects of concentrate discharge into the ocean appear to vary widely and depend on the site-specific environment, the organisms ex- amined, the amount of dilution of the concentrate, and the use of diffuser technology. The ecological impacts of surface water intakes have been well studied for power plants but not for desalination plants, and these impacts will likely vary from place to place. General information on po- tential impacts from groundwater withdrawal and injection are available from decades of hydrogeologic studies for other purposes, but site- specific analyses are necessary to understand the impacts from a pro- posed facility. Once a number of rigorous site-specific studies are con- ducted, this information should be synthesized, using other existing data, to develop an overarching assessment of the possible range of impacts from desalination in the United States. â¢ Monitoring and assessment protocols should be developed for evaluating the potential ecological impacts of surface water con- centrate discharge. Adequate site-specific studies on potential biologi- cal or ecological effects are necessary prior to the development of desali- nation facilities, and planners would benefit from clear guidance on ap- propriate monitoring and assessment protocols. Specific recommenda- tions are provided in Chapter 5. â¢ Longer-term, laboratory-based assays on the sublethal ef- fects of concentrate discharge should be conducted to understand the range of environmental impacts from desalination plants. Except for a few short-term lethality studies that do not give insight into long-term effects, little research has been done on the impacts of concentrate dis- charges on organisms in receiving waters. Longer-term laboratory-based biological assays should evaluate impacts of concentrate on develop- ment, growth, and reproduction using a variety of different organisms, including those native to areas where desalination plants are proposed. These results can be utilized in a risk assessment framework.
Summary 7 â¢ Water quality guidance, based on an analysis of the human health effects of boron in drinking water and considering other sources of exposure, is needed to support decisions for desalination process design. There are concerns about boron in product water from seawater desalination because the boron levels after single-pass RO commonly exceed current WHO health guidelines and the EPA health reference level. A range of water quality levels (0.5 to 1.4 mg/L) have been proposed as protective of public health based on different assump- tions in the calculations. The EPA has decided not to develop a maxi- mum contaminant level for boron because of its lack of occurrence in most groundwater and surface water and has encouraged affected states to issue guidance or regulations as appropriate. Therefore, most U.S. utilities lack clear guidance on what boron levels in drinking water are suitably protective of public health. Boron can be removed through treatment optimization, but that treatment could aversely affect the cost of seawater desalination. â¢ Further research and applications of technology should be carried out on how to mitigate environmental impacts of desalina- tion and reduce potential risks relative to other water supply alter- natives. For example, intake and outfall structures could be designed to minimize impingement and entrainment and to encourage improved dis- persion of the concentrate in coastal discharges. Research could also ex- plore beneficial reuse of the desalination by-products and develop tech- nologies that reduce the volume of this discharge. Desalination efforts do not need to be halted until this research is done and uncertainties are removed, but research investments should be made to help reduce potential risks. COSTS AND BENEFITS OF DESALINATION Historically, the relatively high financial costs of water production via desalination have constrained the use of desalination technologies in all but a few very specific circumstances. As discussed earlier, the finan- cial cost picture has changed in a number of important ways. There have been significant reductions in membrane costs and improvements in the energy efficiency of the desalination process. Perhaps more significant, the costs of other alternatives for augmenting water supplies have con- tinued to rise, making desalination production costs more attractive in a relative sense. The trend of cost reduction may be abetted through a pro- gram of strategically directed research aimed at achieving potentially large cost reductions. Nevertheless, the costs of concentrate management
8 Desalination: A National Perspective are potentially large and vary from site to site. Such costs have the poten- tial to offset reductions in water production costs. The following conclu- sions about the cost and benefits of desalination are based on the discus- sion and analyses in Chapter 6: â¢ Substantial reductions in the financial cost of producing de- salinated water will require substantial reductions in either energy costs or capital costs. Energy and capital costs are the two largest com- ponents of financial cost for both thermal and membrane seawater de- salination processes. Future trends in energy costs also will be important inasmuch as significant increases in energy prices could offset or more than offset cost reductions in other areas and make desalination tech- nologies less attractive. Cost savings are possible if novel technologies or configurations are developed that optimize the use of alternative energy sources, including low-grade or waste energy. â¢ For brackish water desalination, the costs of concentrate management can vary enormously from project to project and may rival energy and capital costs as the largest single component of cost. The high cost of environmentally sustainable concentrate management at some inland locations ultimately offsets the cost advantage that can be obtained from utilizing feed waters with lower salinity. â¢ Conservation and transfers from low- to high-valued uses will usually be less costly than supply augmentation schemes, includ- ing desalination. In many circumstances, there remain methods of de- mand management that can make significant additional quantities of wa- ter available at less cost than desalination. Similarly, market-like trans- fers of water can also offer relatively low-cost ways of acquiring addi- tional supplies of water. Conservation and efficiency improvements that reduce the total demand for water often come with associated benefits, such as reduced energy costs. â¢ There are small but significant efficiencies that can be made in membrane technologies that will reduce the energy needed to de- salinate water and, therefore, offer potentially important process cost reductions. Development of membranes that operate effectively at lower pressures could lead to 5 to 10 percent reductions in total costs of the desalination process associated with a 15 percent decrease in energy use. In contrast, extending membrane life beyond the current 5-year de- sign life is likely to have a small impact on desalination costs because membranes account for a minimal proportion of total costs. Prevention of catastrophic failure through robust pretreatment is important because membrane failure within the first year of operation can cause an annual cost increase of more than 25 percent.
Summary 9 â¢ To make the true costs of desalination transparent, the eco- nomic costs should be accounted for and reported accurately. Failure to price water accurately can lead to inefficient use and overuse. Average cost pricing understates the cost of desalinated water to the consumer, and the supplier should take care in reporting the true and accurate eco- nomic costs publicly. A STRATEGIC DESALINATION RESEARCH AGENDA Over the past 50 years the state of desalination technology has ad- vanced substantially. Even so, concerns about potential environmental impacts continue to limit the application of desalination technology in the United States, and desalination remains a higher-cost alternative for water supply in many communities. In order for desalination to become a more attractive water supply option for communities facing water short- ages, two overarching long-term research goals need to be met: 1. Understand the environmental impacts of desalination and de- velop approaches to minimize these impacts relative to other water sup- ply alternatives, and 2. Develop approaches to lower the financial costs of desalination so that it is an attractive option relative to other alternatives in locations where traditional sources of water are inadequate. Although the environmental impacts of coastal desalination may be less than that of other water supply alternatives, the uncertainty about potential site-specific impacts and their mitigation for both coastal and inland operations are large barriers to the application of desalination in the United States. This uncertainty leads to stakeholder disagreements and a lengthy and costly planning and permitting process. Without rigor- ous scientific research to identify specific potential environmental im- pacts (or a lack of impacts), planners cannot assess the feasibility of de- salination at a site or determine what additional mitigation steps are needed. At present, desalination costs are already low enough to make de- salination an attractive option for some communities when the benefits of desalination are considered, such as providing a drought-resistant supply and providing a means to diversify a large communityâs water supply portfolio. However, the costs of desalination, like the costs of water sup- ply alternatives, are locally variable and are influenced by factors such as site conditions and concentrate management options. In addition, increas- ing awareness of potential environmental impacts is raising the costs of
10 Desalination: A National Perspective permitting and intake and outfall configurations in the United States. Meanwhile, the future costs of energy are uncertain. A strategic research agenda in support of these two overarching goals is described in Chapter 8 (see Box S-1). This research agenda is broadly conceived and includes research that could be appropriately funded and conducted in either the public or the private sector. Several recommendations for implementing the proposed research agenda fol- low: â¢ A coordinated, strategic plan should be developed to ensure that future federal investments in desalination are integrated and prioritized and address the two major goals identified in this report. The strategic application of federal funding for desalination research can advance the implementation of desalination technologies in areas where traditional sources of water are inadequate. Responsibility for developing the plan should rest with the Office of Science and Technology Policy (OSTP). Initial federal appropriations on the order of recent spending on desalination research (total appropriations of about $25 million annually) should be sufficient to make good progress toward these goals, when complemented by ongoing nonfederal and private-sector desalination research, if the funding is directed toward the proposed research topics recommended in this report. Reallocation of current federal spending will be necessary to address currently underfunded topics. If current federal research and development funding is not reallocated, new appropriations will be necessary. However, support for the research agenda stated here should not come at the expense of other high-priority water re- sources research topics. Five years into the implementation of this plan, the OSTP should evaluate the status of the plan, whether goals have been met, and the need for further funding. â¢ Environmental research should be emphasized up front when implementing the research agenda. Uncertainties regarding envi- ronmental impacts and ways to mitigate these impacts are some of the largest hurdles to implementation of desalination in the United States, and research in these areas has the greatest potential for enabling desali- nation to help meet future water needs in communities facing water shortages. Priority areas of environmental research are discussed in Chapters 5 and 8. â¢ Research funding in support of reducing the costs of desali- nation should be directed strategically toward research topics that are likely to make improvements against benchmarks set by the best current technologies for desalination. Because the private sector is al- ready making impressive strides toward reducing the process costs of desalination, the federal research funding should emphasize long-term,
Summary 11 BOX S-1 Priority Research Areas The committee has identified priority research areas to help make desalination a com- petitive option among water supply alternatives for communities facing water shortages. These research areas, which are described in more detail in Chapter 8, are summarized here. The highest priority topics are shown in bold. Some of this research may be most appropriately supported by the private sector. The research topics for which the federal government should have an interestâwhere the benefits are widespread and where no private-sector entities are willing to make the investments and assume the riskâare marked with asterisks. GOAL 1. Understand the environmental impacts of desalination and develop approaches to minimize these impacts relative to other water supply alternatives 1. Assess environmental impacts of desalination intake and concentrate manage- ment approaches** a. Conduct field studies to assess environmental impacts of seawater intakes** b. Conduct field studies to assess environmental impacts of brackish groundwater development** c. Develop protocols and conduct field studies to assess the impacts of concentrate management approaches in inland and coastal settings** d. Develop laboratory protocols for long-term toxicity testing of whole effluent to as- sess long-term impacts of concentrate on aquatic life** e. Assess the environmental fate and bioaccumulation potential of desalination- related contaminants** 2. Develop improved intake methods at coastal facilities to minimize impingement of larger organisms and entrainment of smaller ones** 3. Assess the quantity and distribution of brackish water resources nationwide** 4. Analyze the human health impacts of boron, considering other sources of boron expo- sure, to expedite water-quality guidance for desalination process design** GOAL 2. Develop approaches to lower the financial costs of desalination so that it is an attractive option relative to other alternatives in locations where traditional sources of water are inadequate 5. Improve pretreatment for membrane desalination a. Develop more robust, cost-effective pretreatment processes b. Reduce chemical requirements for pretreatment 6. Improve membrane system performance a. Develop high-permeability, fouling-resistant, high-rejection, oxidant-resistant membranes b. Optimize membrane system design c. Develop lower-cost, corrosion-resistant materials of construction d. Develop ion-selective processes for brackish water e. Develop hybrid desalination processes to increase recovery 7. Improve existing desalination approaches to reduce primary energy use a. Develop improved energy recovery technologies and techniques for desalination b. Research configurations and applications for desalination to utilize waste heat** c. Understand the impact of energy pricing on desalination technology over time** d. Investigate approaches for integrating renewable energy with desalination** 8. Develop novel approaches and/or processes to desalinate water in a way that reduces primary energy use** GOAL 1 and 2 Cross Cuts. 9. Develop cost-effective approaches for concentrate management that minimize potential environmental impacts**
12 Desalination: A National Perspective high-risk research that may not be attempted by the private sector and that is in the public interest. Investigator-driven research should be per- mitted throughout the proposal process. Research cannot address all barriers to increased application of de- salination technology in regions facing water scarcity concerns; thus, practical desalination implementation issues that pertain to water provid- ers are discussed in Chapter 7. Recommendations in Chapter 7 include building trust and educating the public on desalination project planning, anticipating the sometimes cumbersome regulatory and permitting proc- ess, and utilizing pilot testing to optimize the process design. PROSPECTS FOR DESALINATION The potential for desalination to meet anticipated water demands in the United States is constrained not by the source water resources or the capabilities of current technology, but by a variety of financial, social, and environmental factors. Substantial uncertainty remains about the en- vironmental impacts of desalination, and resolving these uncertainties and developing methods to mitigate the impacts is the highest priority for future research. Research and development also are needed to continue current trends in reducing the process costs of desalination and develop- ing cost-effective, environmentally sustainable approaches for concen- trate management. Implementing the proposed research agenda will re- quire federal leadership and a coordinated, strategic plan among multiple agencies. In addition, the success of the research agenda will depend on participation by federal, state, local agencies, nongovernmental entities, and the private sector.