|
||||||||||||||||
|
||||||||||||||||
The following HTML text is provided to enhance online readability. Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy. 8
|
||||||||||||||||
 |
 |
Page 212 |
 |
 |
 |
|
| ||||||||||||||||||||||||||||||||
|
|
|||||||||||||||||||||||||||||||
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 212
Desalination: A National Perspective
8
A Strategic Research Agenda for Desalination
As noted in Chapter 3, desalination is likely to have a niche in the water management portfolio of the future, although the significance of this niche cannot be definitively determined at this time. The potential for desalination to meet anticipated water demands in the United States is not constrained by the source water resources or the capabilities of current technology, but instead it is constrained by financial, social, and environmental factors. Over the past 50 years the state of desalination technology has advanced substantially, and improvements in energy recovery and declining membrane material costs have made brackish water and seawater desalination a more reasonable option for some communities. However, desalination remains a higher-cost alternative for water supply in many communities, and concerns about potential environmental impacts continue to limit the application of desalination technology in the United States. For inland desalination facilities, there are few, if any, cost-effective environmentally sustainable concentrate management technologies. Meanwhile, as noted in Chapter 2, there is no integrated and strategic direction to current federal desalination research and development efforts to help address these concerns.
In this chapter, long-term research goals are outlined for advancing desalination technology and improving the ability of desalination to address U.S. water supply needs. A strategic national research agenda is then presented to address these goals. This research agenda is broadly conceived and includes research that could be appropriately funded and conducted in either the public or private sectors. The committee recognizes that research cannot address all barriers to increased application of desalination technology in regions facing water scarcity concerns; therefore, practical implementation issues are discussed separately in Chapter 7. Recommendations related to implementing the proposed research agenda are also provided in this chapter.
OCR for page 213
Desalination: A National Perspective
LONG-TERM RESEARCH GOALS
Based on the committee’s analyses of the state of desalination technology, potential environmental impacts, desalination costs, and implementation issues in the United States (see Chapters 4-7), the committee developed two overarching long-term goals for further research in desalination:
Understand the environmental impacts of desalination and develop approaches to minimize these impacts relative to other water supply alternatives, and
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.
Understanding the potential environmental impacts of desalination in both inland and coastal communities and developing approaches to mitigate these impacts relative to other alternatives are essential to the future of desalination in the United States. The environmental impacts of both source water intakes and concentrate discharge remain poorly understood. Although the impacts of coastal desalination are suspected to be less than those of other water supply alternatives, the uncertainty about potential site-specific impacts and their mitigation are large barriers to the application of coastal desalination in the United States. This uncertainty leads to stakeholder disagreements and a lengthy and costly planning and permitting process. For inland desalination, uncertainties remain about the sustainability of brackish groundwater resources and the environmental impacts from concentrate discharge to surface waters. Without rigorous scientific research to identify specific potential environmental impacts (or a lack of impacts), planners cannot assess the feasibility of desalination at a site or determine what additional mitigation steps are needed. Once potential impacts are clearly understood, research can be focused on developing approaches to minimize these impacts.
The second goal focuses on the cost of desalination relative to the cost of other water supply alternatives. At present, costs are already low enough to make desalination an attractive option for some communities, especially where concentrate management costs are modest. In fact, desalination plants are being studied or implemented in at least 30 municipalities nationwide (GWI, 2007). The economic costs of desalination, however, as well as the costs of water supply alternatives, are locally variable. Costs are influenced by factors such as source water quality, siting considerations, potential environmental impacts, local regulations and permitting requirements, and available concentrate management op-
OCR for page 214
Desalination: A National Perspective
tions. Desalination remains a higher-cost alternative for many locations, and increasing awareness of potential environmental impacts is raising the costs of permitting and intake and outfall configurations in the United States. Inland communities considering brackish groundwater desalination may soon face more restrictions on surface water discharge and, therefore, will have fewer low-cost alternatives for concentrate management. Meanwhile, the future costs of energy are uncertain. If the total costs of desalination (including environmental costs) were reduced relative to other alternatives, desalination technology would become an attractive alternative to help address local water supply needs.
STRATEGIC DESALINATION RESEARCH AGENDA
The committee identified research topics as part of a strategic agenda to address the two long-term research goals articulated earlier. This agenda is driven by determination of what is necessary to make desalination a competitive option among other water supply alternatives. The agenda is broadly conceived, including research topics of clear interest to the public sector—and therefore of interest for federal funding—and research that might be most appropriately funded by private industry. The suggested research areas are described in detail below and are summarized in Box 8-1. Specific recommendations on the roles of federal and nonfederal organizations in funding the agenda are described in an upcoming section.
BOX 8-1
Priority Research Areas
The committee has identified priority research areas to help make desalination a competitive option among water supply alternatives for communities facing water shortages. These research areas, which are described in more detail in the body of the chapter, 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 interest—where the benefits are widespread and where no private-sector entities are willing to make the investments and assume the risk—are marked with asterisks.
GOAL 1. Understand the environmental impacts of desalination and develop approaches to minimize these impacts relative to other water supply alternatives
Assess environmental impacts of desalination intake and concentrate management approaches**
OCR for page 215
Desalination: A National Perspective
Conduct field studies to assess environmental impacts of brackish groundwater development**
Develop protocols and conduct field studies to assess the impacts of concentrate management approaches in inland and coastal settings**
Develop laboratory protocols for long-term toxicity testing of whole effluent to assess long-term impacts of concentrate on aquatic life**
Assess the environmental fate and bioaccumulation potential of desalination-related contaminants**
Develop improved intake methods at coastal facilities to minimize impingement of larger organisms and entrainment of smaller ones**
Assess the quantity and distribution of brackish water resources nationwide**
Analyze the human health impacts of boron, considering other sources of boron exposure, 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
Improve pretreatment for membrane desalination
Develop more robust, cost-effective pretreatment processes
Reduce chemical requirements for pretreatment
Improve membrane system performance
Develop high-permeability, fouling-resistant, high-rejection, oxidant-resistant membranes
Optimize membrane system design
Develop lower-cost, corrosion-resistant materials of construction
Develop ion-selective processes for brackish water
Develop hybrid desalination processes to increase recovery
Improve existing desalination approaches to reduce primary energy use
Develop improved energy recovery technologies and techniques for desalination
Research configurations and applications for desalination to utilize low-grade or waste heat**
Understand the impact of energy pricing on desalination technology over time**
Investigate approaches for integrating renewable energy with desalination**
Develop novel approaches or processes to desalinate water in a way that reduces primary energy use**
GOAL 1 and 2 Crosscuts
Develop cost-effective approaches for concentrate management that minimize potential environmental impacts**
OCR for page 216
Desalination: A National Perspective
Research on Environmental Impacts
The following research topics address Goal 1 to understand the environmental impacts of desalination and develop approaches to minimize those impacts relative to other water supply alternatives.
Assess environmental impacts of desalination intake and concentrate management approaches
As discussed in Chapter 5, the environmental impacts of desalination source water intake and concentrate management approaches are not well understood. Source water intakes for coastal desalination can create entrainment concerns with small organisms and impingement issues for larger organisms. For inland groundwater desalination, there are potential concerns regarding overpumping, water quality changes, and subsidence. The possible environmental impacts of concentrate management approaches range from effects on aquatic life in surface water discharges to the contamination of drinking water aquifers in poorly designed injection wells or ponds. Both site-specific studies and broad analyses of relative impacts would help communities weigh the alternatives for meeting water supply needs. The specific research needs are described as follows.
1a. Conduct field studies to assess environmental impacts of seawater intakes. Measurements and modeling of the extent of mortality of aquatic or marine organisms due to impingement and entrainment are needed. There have been numerous studies on such impacts of power plants, and extrapolation of such effects to desalination facilities should be performed.
1b. Conduct field studies to assess environmental impacts of brackish groundwater development. The general environmental interactions between wetlands, freshwater, and brackish aquifers for inland sources have not been documented under likely brackish water development scenarios. While site-specific evaluation of any location will be necessary for developing a brackish water resource, the lack of synthesized information is an impediment to the use of this resource for smaller communities with limited resources.
1c. Develop protocols and conduct field studies to assess the impacts of concentrate management approaches in inland and coastal settings. Comprehensive studies analyzing impacts of concentrate discharge at marine, estuarine, and inland desalination locations are needed.
OCR for page 217
Desalination: A National Perspective
Adequate site-specific baseline studies on potential biological and ecological effects are necessary prior to the development of desalination facilities because biological communities in different geographic areas will have differential sensitivity, but a comprehensive synthesis would be valuable once several in-depth studies have been conducted. Protocols should be developed to define the baseline and operational monitoring, reference sites, lengths of transects, and sampling frequencies. Planners would benefit from clear guidance on appropriate monitoring and assessment protocols. Environmental data should be collected for at least 1 year in the area of the proposed facility before a desalination plant with surface water concentrate discharge comes online so that sufficient baseline data on the ecosystem are available with which to compare postoperating conditions. Once a plant is in operation, monitoring of the ecological communities (especially the benthic community) receiving the concentrate should be performed periodically for at least 2 years at multiple distances from the outflow pipe and compared to reference sites.
For inland settings, additional regional hydrogeology research is needed on the distribution, thickness, and hydraulic properties of formations that could be used for disposal of concentrate via deep-well injection. Much information is already available about the potential for deep-well injection in states such as Florida and Texas, although suitable geologic conditions may exist in other states as well. Inventories of industrial and commercial brine-disposal wells and producing and abandoned oil fields should be synthesized and used to develop a suitable protocol for further hydrogeological investigations, as appropriate. This research would provide valuable assistance to small communities that typically do not have the resources available to support extensive hydrogeological investigations.
1d. Develop laboratory protocols for long-term toxicity testing of whole effluent to assess long-term impacts of concentrate on aquatic life. Standard acute toxicity tests as defined by the U.S. Environmental Protection Agency (EPA) are generally 96 hours in duration and use larval or juvenile stages of certain fish and invertebrate species with a series of effluent dilutions and a control. The end point is whether the test organisms survive or not. Chronic tests, according to EPA, are typically 7 days in duration when using larval stages of fish and invertebrate species, and the end points of the tests are sublethal, such as growth reduction. Typical chronic toxicity protocols were designed for testing municipal or industrial wastewater treatment plant effluent, which typically contains higher levels of toxic chemicals than the concentrate from desalination plants. To assess the impacts of desalination effluent, a protocol should be developed to analyze the longer-term effects (over whole life cycles) on organisms that live in the vicinity of desalination plants (as opposed
OCR for page 218
Desalination: A National Perspective
to the standard species used in EPA-required toxicity testing). These laboratory-based tests should then be used to examine the impacts of whole effluent (and various dilutions) from different desalination plants on a variety of different taxa at numerous representative sites from key ecological regions.
1e. Assess the environmental fate and bioaccumulation potential of desalination-related contaminants. Desalination concentrate contains more than just salts and may include various chemicals that are used in pretreatment and membrane cleaning, antiscaling and antifoulant additives, and metals that may leach from corrosion. Some of these chemicals (e.g., antifoulants, copper leached from older thermal desalination plants) or chemical by-products (e.g., trihalomethanes produced as a result of pretreatment with chlorine) are likely to bioaccumulate in organisms. Investigations into the loading and environmental fate of desalination-related chemicals should be included in modeling and monitoring programs. The degree to which various chemicals biodegrade or accumulate in sediments should also be investigated. High priority should be given to polymer antiscalants, such as polycarbonic acids and polyphosphate, which may increase primary productivity. Corrosion-related metals and disinfection by-products should also be investigated. In conjunction with the field studies described earlier, representative species, preferably benthic infauna along the transects and from the reference (control) site, should be analyzed for bioaccumulative contaminants. Because little is known about the potential of some other desalination chemicals that can be discharged in concentrate to bioaccumulate (e.g., polyphosphate, polycarbonic acid, polyacrylic acid, polymaleic acid), research should be conducted into their toxicity and bioaccumulation potential.
Develop improved intake methods at coastal facilities to minimize impingement of larger organisms and entrainment of smaller ones
Although intake and screen technology is rapidly developing, continued research and development is needed in the area of seawater intakes to develop cost-effective approaches that minimize the impacts of impingement and entrainment for coastal desalination facilities. Current technology development has focused on subsurface intakes and advanced screens or curtains, and these recent developments should be assessed to determine the costs and benefits of the various approaches. Other innovative concepts could also be considered that might deter marine life from entering intakes.
OCR for page 219
Desalination: A National Perspective
Assess the quantity and distribution of brackish water resources nationwide
Sustainable development of inland brackish water resources requires maps and synthesized information on total dissolved solids of the groundwater, types of dominant solutes (e.g., NaCl, CaSO4), thickness, and depth to brackish water. The only national map of brackish water resources available (Feth, 1965; Figure 1-1) simply shows depth to saline water. Newer and better solute chemistry data collected over the past 40 years exist in the files of private, state, and federal offices but are not generally organized for use in brackish water resources investigations. Using the aforementioned information, basin analyses, analogous to the U.S. Geological Survey Regional Aquifer System Analysis program for freshwater, could be developed, emphasizing regions facing near-term water scarcity concerns. These brackish water resource investigations could also be conducted at the state level. The data, once synthesized, could be utilized for desalination planning as well as for other water resources and commercial development scenarios.
Analyze the human health impacts of boron, considering other sources of boron exposure, to expedite water-quality guidance for desalination process design
Typical single-pass reverse osmosis (RO) desalination processes do not remove all the boron in seawater; thus, boron can be found at milligram-per-liter levels in the finished water. Boron can be controlled through treatment optimization, but that treatment has an impact on the cost of desalination. A range of water quality levels (0.5 to 1.4 mg/L) have been proposed as protective of public health based on different assumptions in the calculations. Because of the low occurrence of boron in most groundwater and surface water, the EPA has decided not to develop a maximum contaminant level for boron and has encouraged affected states to issue guidance or regulations as appropriate (see Chapter 5). Additional analysis of existing boron toxicity data is needed, considering other possible sources of boron exposure in the United States, to support guidance for desalination process design that will be suitably protective of human health.
OCR for page 220
Desalination: A National Perspective
Research to Lower the Costs of Desalination
The following research topics address Goal 2 to develop approaches to lower the costs of desalination so that it is an attractive option relative to other alternatives in locations where traditional sources of water are inadequate. As a broadly conceived agenda, some of this research may be most appropriately supported by the private sector. The appropriate roles of governmental and nongovernmental entities to fund the research agenda are discussed later in the chapter.
Improve pretreatment for membrane desalination
Pretreatment is necessary to remove potential foulants from the source water, thereby ensuring sustainable operation of the RO membranes at high product water flux and salt rejection. Research to improve the pretreatment process is needed that would develop alternative, cost-effective approaches.
5a. Develop more robust, cost-effective pretreatment processes. Membrane fouling is one of the most problematic issues facing seawater desalination. Forms of fouling common with RO membranes are organic fouling, scaling, colloidal fouling, and biofouling. All forms of fouling are caused by interactions between the foulant and the membrane surface. Improved pretreatment that minimizes these interactions will reduce irreversible membrane fouling. Alteration of solution characteristics can improve the solubility of the foulants, preventing their precipitation or interaction with the membrane surface. Such alteration could be chemical, electrochemical, or physical in nature.
Membranes such as microfiltration (MF) and ultrafiltration (UF) have several advantages over traditional pretreatment (e.g., conventional sand filtration) because they have a smaller footprint, are more efficient in removing smaller foulants, and provide a more stable influent to the RO membranes. Additional potential benefits of MF or UF pretreatment are increased flux, increased recovery, longer membrane life, and decreased cleaning frequency. More research is necessary in order to optimize the pretreatment membranes for more effective removal of foulants to the RO system, to reduce the fouling of the pretreatment membranes, and to improve configuration of the pretreatment membranes to maximize cost reduction.
5b. Reduce chemical requirements for pretreatment. Antiscalants, coagulants, and oxidants (such as chlorine) are common chemicals
OCR for page 221
Desalination: A National Perspective
applied in the pretreatment steps for RO membranes. Although these chemicals are added to reduce fouling, they add to the operational costs, can reduce the operating life of membranes, and have to be disposed of properly or they can adversely impact aquatic life (see Chapter 5). Antiscalants may also enhance biofouling, so alternative formulations or approaches should be examined. Research is needed on alternative formulations or approaches (including membrane pretreatment) to reduce the chemical requirements of the pretreatment process, both to reduce overall cost and to decrease the environmental impacts of desalination.
Improve membrane system performance
Sustainable operation of the RO membranes at the designed product water flux and salt rejection is a key to the reduction of desalination process costs. In addition to effective pretreatment, research to optimize the sustained performance of the RO membrane system is needed.
6a. Develop high-permeability, fouling-resistant, high-rejection, oxidant-resistant membranes. New membrane designs could reduce the treatment costs of desalination by improving membrane permeability and salt rejection while increasing resistance to fouling and membrane oxidation. Current membrane research to reduce fouling includes altering the surface charge, increasing hydrophilicity, adding polymers as a barrier to fouling, and decreasing surface roughness.
Oxidant-resistant membranes enable feedwater to maintain an oxidant residual that will reduce membrane fouling due to biological growth. Current state-of-the-art thin-film composite desalination membranes are polyamide based and therefore are vulnerable to damage by chlorine or other oxidants. Thus, when an oxidant such as chlorine is added to reduce biofouling, dechlorination is necessary to prevent structural damage. Additionally, trace concentrations of chlorine may be present in some feedwaters. Cellulose-derivative RO membranes have much higher chlorine tolerance; however, these membranes have a much lower permeability than thin-film composite membranes and operate under a narrower pH range. Therefore, there is a need to increase the oxidant tolerance of the higher-permeability membranes. Lower risk of premature membrane replacement equates to overall lower operating costs.
Past efforts to synthesize RO membranes with high permeability often resulted in reduced rejection and selectivity. There is a need to develop RO membranes with high permeability without sacrificing selectivity or rejection efficiency. Recent research on utilizing nanomaterials, such as carbon nanotubes, as a separation barrier suggest the possibility
OCR for page 222
Desalination: A National Perspective
of obtaining water fluxes much higher than that of traditional polymeric membranes.
The development of membranes that are more resistant to degradation from exposure to cleaning chemicals will extend the useful life of a membrane module. The ability to clean membranes more frequently can also decrease energy usage because membrane fouling results in higher differential pressure loss through the modules. By extending the life of membrane modules, the operating and maintenance cost will be reduced by the associated reduction in membrane replacements required.
6b. Optimize membrane system design. With the development of high-flux membranes and larger-diameter membrane modules, new approaches for optimal RO system design are needed to avoid operation under thermodynamic restriction (see Chapter 4) and to ensure equal distribution of flux between the leading and tail elements of the RO system. The key variables for the system design will involve the choice of optimal pressure, the number of stages, and number and size of membrane elements at each stage. An optimal system configuration may also involve hybrid designs where one type of membrane (e.g., intermediate flux, highly fouling-resistant) is used in the leading elements followed by high-flux membranes in the subsequent elements. Fouling can be mitigated by maintaining high crossflow velocity; thus, fouling-resistant membranes may be better served in the downstream positions where lower crossflow velocity is incurred. Thus, additional engineering research on membrane system design is needed to optimize performance with the objective of reducing costs.
6c. Develop lower-cost, corrosion-resistant materials of construction. The duration of equipment life in a desalination plant directly relates to the total costs of the project. Saline and brackish water plants are considered to be a corrosive environment due to the high levels of salts in the raw water. The development and utilization of corrosion-resistant materials will minimize the frequency of equipment or appurtenance replacement, which can significantly reduce the total project costs.
6d. Develop ion-selective processes for brackish water. Some slightly brackish waters could be made potable simply though specific removal of certain contaminants, such as nitrate or arsenite, while removing other ions such as sodium, chloride, and bicarbonate at a lower rate. High removal rates of all salts are not necessary for such waters. Ion-specific separation processes, such as an ion-selective membrane or a selective ion-exchange resin, should be able to produce potable water at much lower energy costs than those processes that fully desalinate the
OCR for page 223
Desalination: A National Perspective
source water. Ion-selective removal would also create fewer waste materials requiring disposal. Ion-selective processes would be useful for mildly brackish groundwater sources with high levels of nitrate, uranium, radium, or arsenic. Such an ion-selective process could also be used to optimize boron removal following RO desalination of seawater.
6e. Develop hybrid desalination processes to increase recovery. Overall product water recovery in a desalination plant can be increased through the serial application of more than one desalination process. For example, an RO process could be preceded by a “tight” nanofiltration process, allowing the RO to operate at a higher recovery than it could with less aggressive pretreatment. Other options could be devised, including hybrid thermal and membrane processes to increase the overall recovery of the process. As noted in Chapter 4, the possible hybrid combinations of desalination processes are limited only by ingenuity and identification of economically viable applications. Hybridization also offers opportunities for reducing desalination production costs and expanding the flexibility of operations, especially when co-located with power plants, but hybridization also increases plant complexity and raises challenges in operation and automation.
Improve existing desalination approaches to reduce primary energy use
Energy is one of the largest annual costs in the desalination process. Thus, research to improve the energy efficiency of desalination technologies could make a significant contribution to reducing costs.
7a. Develop improved energy recovery technologies and techniques for desalination. Membrane desalination is an energy-intensive process compared to treatment of freshwater sources. Modern energy recovery devices operate at up to 96 percent energy recovery (see Chapter 4), although these efficiencies are lower at average operating conditions. The energy recovery method in most common use today is the energy recovery (or Pelton) turbine, which achieves about 87 percent efficiency. Many modern plants still use Pelton wheels because of the higher capital cost of isobaric devices. Thus, opportunities exist to improve recovery of energy from the desalination concentrate over a wide operating range and reduce overall energy costs.
7b. Research configurations and applications for desalination to utilize low-grade or waste heat. Industrial processes that produce waste or low-grade heat may offer opportunities to lower the operating cost of
OCR for page 224
Desalination: A National Perspective
the desalination process if these heat sources are co-located with desalination facilities (see Box 4-8). Low-grade heat can be used as an energy source for desalination via commercially available thermal desalination processes. Hybrid membrane-thermal desalination approaches offer additional operational flexibility and opportunities for water-production cost savings. Research is needed to examine configurations and applications of current technologies to utilize low-grade or waste heat for desalination.
7c. Understand the impact of energy pricing on existing desalination technology over time. Energy is one of the largest components of cost for desalination, and future changes in energy pricing could significantly affect the affordability of desalination. Research is needed to examine to what extent the economic and financial feasibility of desalination may be threatened by the uncertain prospect of energy price increases in the future for typical desalination plants in the United States. This research should also examine the costs and benefits of capital investments in renewable energy sources.
7d. Investigate approaches for integrating renewable energy with desalination. Renewable energy sources could help mitigate future increases in energy costs by providing a means to stabilize energy costs for desalination facilities while also reducing the environmental impacts of water production. Research is needed to optimize the potential for coupling various renewable energy applications with desalination.
Develop novel approaches or processes to desalinate water in a way that reduces primary energy use
Because the energy of RO is only twice the minimum energy of desalination, even novel technologies are unlikely to create step change (>25 percent) reductions in absolute energy consumption compared to the best current technology (see, e.g., Appendix A). Instead, substantial reductions in the energy costs of desalination are more likely to come through the development of novel approaches or processes that optimize the use of low-grade heat. Several innovative desalination technologies that are the focus of ongoing research, such as forward osmosis, dewvaporation, and membrane distillation, have the capacity to use low-grade heat as an energy source. Research into the specific incorporation of waste or low-grade heat into these or other innovative processes could greatly reduce the amount of primary energy required for desalination and, thus, overall desalination costs.
OCR for page 225
Desalination: A National Perspective
Crosscutting Research
Research topics in this category benefit both Goal 1, for environmental impacts, and Goal 2, for lowering the cost of desalination.
Develop cost-effective approaches for concentrate management that minimize potential environmental impacts
Research objectives related to concentrate management are crosscutting, because they address both the need to understand and minimize environmental impacts and the need to reduce the total cost of desalination. For coastal concentrate management, research is needed to develop improved diffuser technologies and subsurface injection approaches and to examine their costs and benefits relative to current disposal alternatives.
The high cost of inland concentrate management inhibits inland brackish water desalination. Low- to moderate-cost concentrate management alternatives (i.e., subsurface injection, land application, sewer discharge, and surface water discharge) can be limited by the salinity of the concentrate and by location and climate factors; in some scenarios all of these options may be restricted by site-specific conditions, leaving zero liquid discharge (ZLD) as the only alternative for consideration. ZLD options currently include evaporation ponds and energy-intensive processes, such as brine concentrators or crystallizers, followed by landfilling. These options have high capital or operating costs. Research to improve recovery in the desalination process and thereby minimize the initial volume of concentrate could enhance the practical viability of several concentrate management options for inland desalination. This is particularly true for the concentrate management options that are characterized by high costs per unit volume of the concentrate flow treated and for approaches that are not applicable to large concentrate flows, such as thermal evaporation or evaporation ponds. Advancements are also needed that reduce the capital costs and improve the energy efficiency of thermal evaporation processes. Conventional concentrate management options that involve simple equipment are not likely to see significant cost reductions through additional research.
The reuse of high-salinity concentrates and minerals extracted from them should be further explored and developed to help mitigate environmental impacts while generating revenues that can help offset concentrate management costs. Possibilities include selective precipitation of marketable salts, irrigation of salt-tolerant crops, supplements for animal dietary needs, dust suppressants, stabilizers for road base construction, or manufacture of lightweight fire-proof building materials. Studies are
OCR for page 226
Desalination: A National Perspective
necessary to determine the most feasible uses and to develop ways to prepare the appropriate product for various types of reuse. For all possible uses, site-specific limitations and local and state regulations will need to be considered. Because the transportation costs greatly affect the economics of reuse, a market analysis would also be needed to identify areas in the United States that could reasonably utilize products from desalination concentrate.
Highest Priority Research Topics
All of the topics identified are considered important, although three topics (1, 2, and 9 above) were deemed to be the highest priority research topics: (1) assessing the environmental impacts of desalination intake and concentrate management approaches, (2) developing improved intake methods to minimize impingement and entrainment, and (3) developing cost-effective approaches for concentrate management that minimize environmental impacts. These three research areas are considered the highest priorities because this research can help address the largest barriers (or showstoppers) to more widespread use of desalination in the United States. Uncertainties about potential environmental impacts will need to be resolved and cost-effective mitigation approaches developed if desalination is to be more widely accepted. Research to develop cost-effective approaches for concentrate management is critical to enable more widespread use of desalination technologies for inland communities. As noted in Chapter 4, the cost of concentrate management can double or triple the cost of the desalination for some inland communities.
Research may also reduce the costs of desalination. Any cost improvement will help make desalination an attractive option for communities addressing water shortages. However, the committee does not view these process cost issues as the major limitation to the application of desalination in the United States today.
IMPLEMENTING THE RESEARCH AGENDA
In the previous section, the committee proposed a broad research agenda that, if implemented, should improve the capacity of desalination to meet future water needs in the United States by further examining and addressing its environmental impacts and reducing its costs relative to other water supply alternatives. Implementing this agenda requires federal leadership, but its success depends on participation from a range of entities, including federal, state, and local governments, nonprofit or-
OCR for page 227
Desalination: A National Perspective
ganizations, and the private sector. A strategy for implementing the research agenda is suggested in the following section. This section also includes suggestions for funding the agenda and the appropriate roles of government and nongovernmental entities.
Supporting the Desalination Research Agenda
A federal role is appropriate for research that provides a “public good.” Specifically, the federal government should have an interest in funding research where the benefits are widespread but where no private-sector entities are willing to make the investment and assume the risks. Thus, for example, research that results in significant environmental benefits should be in the federal interest because these benefits are shared by the public at large and cannot be fully captured by any entrepreneur. Federal investment is also important where it has “national significance”—where the issues are of large-scale concern; they are more than locally, state-, or regionally specific; and the benefits accrue to a large swath of the public.
Based on the aforementioned criteria, the proposed research agenda contains many topic items that should be in the federal interest (see topics marked with asterisks in Box 8-1). The research topics in support of Goal 1 (see Box 8-1) are directed at environmental issues that are largely “public good” issues. Some of the needed environmental research will, by nature, be site-specific, and purely site-specific research is not of great federal interest. Thus, there is a clear role for state and local agencies to support site-specific research. The federal government, however, should have an interest in partnering with local communities to conduct more extensive field research from which broader conclusions of environmental impacts can be drawn or which would significantly contribute to a broader meta-analysis. This meta-analysis could especially benefit small water supply systems. Also, there should be federal interest in establishing general protocols for field evaluations and chronic bioassays that could then be adapted for site-specific studies.
The research needed to support the attainment of Goal 2 includes several topics that are clearly in the federal interest, as defined earlier. These include efforts to reduce prime energy use, to integrate renewable energy resources within the total energy picture and increase reliance upon them, and to understand the impacts of energy pricing on the future of desalination (see highlighted topics in Box 8-1). However, Goal 2 also includes a number of research topics that may be more appropriately funded by the private sector or nongovernmental organizations, assuming that these entities are willing to assume the risks of the research investment. Indeed, private industry already spends far more on research and
OCR for page 228
Desalination: A National Perspective
development for desalination than the federal government (see Chapter 2) and is already making substantial progress in the improvement of existing membrane performance, developing better pretreatment alternatives, and developing improved energy recovery devices. To avoid duplication and to optimize available research funding, government programs should focus instead on research and development with widespread possible benefits that would otherwise go unfunded because private industry is unwilling to make the investment. Finally, the crosscutting topic to develop cost-effective methods of managing concentrates for inland communities, which impacts Goals 1 and 2, is also in the federal interest.
Federal Research Funding
The optimal level of federal investment in desalination research is inherently a question of public policy. Although the decision should be informed by science, it is not—at its heart—a scientific decision. However, several conclusions emerged from the committee’s analysis of current research and development funding (see Chapter 2) that suggest the importance of strategic integration of the research program. The committee concluded that 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 nation well and will require the expenditure of more funds than necessary to achieve specified goals.
To ensure that future federal investments in desalination research are integrated and prioritized so as to address the two major goals identified in this report, the federal government will need to develop a coordinated strategic plan that utilizes the recommendations of this report as a basis. It is beyond the committee’s scope to recommend specific plans for improving coordination among the many federal agencies that support desalination research. Instead, responsibility for developing the plan should rest with the Office of Science and Technology Policy’s (OSTP’s) National Science and Technology Council (NSTC) because “this Cabinet-level Council is the principal means within the executive branch to coordinate science and technology policy across the diverse entities that make up the Federal research and development enterprise.”1 For example, the NSTC’s Subcommittee on Water Availability and Quality has member-ship representing more than 20 federal agencies and recently released “A Strategy for Federal Science and Technology to Support Water Avail-
1
For more information, see http://www.ostp.gov/nstc/index.html.
OCR for page 229
Desalination: A National Perspective
ability and Quality in the United States” (SWAQ, 2007). Representatives of the National Science Foundation, the Bureau of Reclamation, the Environmental Protection Agency, the National Oceanographic and Atmospheric Administration, the Office of Naval Research, and the Department of Energy should participate fully in the development of the strategic federal plan for desalination research and development. 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.
A coordinated strategic plan governing desalination research at the federal level along with effective implementation of the research plan will be the major determinants of federal research productivity in this endeavor. The committee cannot emphasize strongly enough the importance of a well-organized, well-articulated strategically directed effort. In the absence of any or all of these preconditions, federal investment will yield less than it could. Therefore, a well-developed and clearly articulated strategic research plan, as called for above, should be a precondition for any new federal appropriations.
Initial federal appropriations on the order of recent spending on desalination research (total appropriations of about $25 million annually, as in fiscal years 2005 and 2006) should be sufficient to make good progress toward the overall research goals if the funding is strategically directed toward the proposed research topics as recommended in this report. Annual federal appropriations of $25 million, properly allocated, should be sufficient to have an impact in the identified priority research areas, given the context of expected state and private-sector funding. This level of federal funding is also consistent with NRC (2004a), which recommended annual appropriations of $700 million for research supporting the nation’s entire water resources research agenda. Reallocation of current spending will be necessary to address topics that are currently underfunded. If current research funding is not reallocated, the overall desalination research and development budget will need to be enhanced. Nevertheless, support for the research agenda stated here should not come at the expense of other high-priority water resource research topics, such as those identified in Confronting the Nation’s Water Problems: The Role of Research (NRC, 2004a).
Environmental research should be emphasized up front in the research agenda. At least 50 percent of the federal funding for desalination research should initially be directed toward environmental research. Environmental research, including Goal 1 and the Goal 1 and 2 crosscuts, should be addressed, because these have the potential for the greatest impact in overcoming current roadblocks for desalination and making desalination an attractive water supply alternative. Research funding in support of Goal 2 should be directed strategically toward research topics that are likely to make improvements against benchmarks set by the best
OCR for page 230
Desalination: A National Perspective
current technologies for desalination. The best available technologies for desalination at the time of this writing are benchmarked in Chapter 4. Research proposals should make the case as to how and to what degree the proposed research can advance the state of the art in desalination. An emphasis should be placed on energy benchmarks because reductions in energy result in overall cost savings and have environmental benefits. The majority of the federal funding directed toward Goal 2 should support projects that are in the public interest and would not otherwise be privately funded (see Box 8-1), such as some high-risk and long-term research initiatives (e.g., developing novel desalination processes that sharply reduce the primary energy use). Although private industry does make modest investments in high-risk research, it is frequently reluctant to invest in research in the earliest stage of technology creation, when there is extremely low likelihood of success even though there are large potential benefits.
The effectiveness with which federal funds are spent will also depend on certain critical implementation steps, which are outlined in the following section.
Proposal Announcement and Selection
Based on available funding, the opportunity to announce requests for proposals exists for federal agencies, such as the Bureau of Reclamation or the National Science Foundation, or other research institutions that explicitly target one or more research objectives. The principal funding agency should announce a request for proposals as widely as possible to scientists and engineers in municipal and federal government, academia, and private industry. At present, the desalination community is relatively small, but collectively there is a great deal of expertise across the world. International desalination experts and others from related areas of research should be encouraged and given the opportunity to offer innovative research ideas that have the potential to significantly advance the field. Thus, the request for proposals should extend to federal agencies, national laboratories, other research institutions, utilities, and the private sector. Since innovation cannot be preassigned, broad solicitations for proposals should include a provision for unsolicited investigator-initiated research proposals.
To achieve the objectives of the research agenda, proposals should be selected through a rigorous independent peer-review process (NRC, 2002b) irrespective of the agency issuing the request for proposals. A rotating panel of independent, qualified reviewers should be appointed based on their relevant expertise in the focal areas. The process should
OCR for page 231
Desalination: A National Perspective
allow for the consideration and review of unsolicited proposals, as long as their research goals meet the overall research goals. Proposal funding should be based on the quality of the proposed work, the degree to which the proposed research can advance the state of the art in desalination or otherwise contribute toward the research goals, prior evidence of successful research, and the potential for effective publication or dissemination of the research findings.
CONCLUSIONS AND RECOMMENDATIONS
A strategic national research agenda has been conceived that centers around two overarching strategic goals for further research in desalination: (1) to understand the environmental impacts of desalination and develop approaches to minimize 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. A research agenda is proposed in this chapter in support of these two goals (see Box 8-1). Several recommendations for implementing the proposed research agenda follow.
A coordinated strategic plan should be developed to ensure that future federal investments in desalination research 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 OSTP, which should use the recommendations of this report as a basis for plan development. 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 as recommended in this chapter. 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 resource 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.
OCR for page 232
Desalination: A National Perspective
Environmental research should be emphasized up front when implementing the research agenda. Uncertainties regarding environmental impacts and ways to mitigate these impacts are one of the largest hurdles to implementation of desalination in the United States, and research in these areas has the greatest potential for enabling desalination to help meet future water needs in communities facing water shortages. This environmental research includes work to understand environmental impacts of desalination intakes and concentrate management, the development of improved intake methods to minimize impingement and entrainment, and cost-effective concentrate management technologies.
Research funding in support of reducing the costs of desalination (Goal 2) 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 already making impressive strides toward Goal 2, federal research funding should emphasize the long-term and high-risk research that may not be attempted by the private sector and that is in the public interest, such as research on novel technologies that significantly reduce prime energy use.
Wide dissemination of requests for proposals to meet the goals of the research agenda will benefit the quality of research achieved. Requests for proposals should extend to federal agencies, national laboratories, research institutions, utilities, other countries, and the private sector. Investigator-driven research through unsolicited proposals should be permitted throughout the proposal process. Proposals should be peer-reviewed and based on quality of research proposed, the potential contribution, prior evidence of successful research, and effective dissemination.