Desalination: Water from Water

By Jane Kucera

“Blue is the new green.”  This is an all-new revised edition of a modern classic on one of the most important subjects in engineering: Water. Featuring a total revision of the initial volume, this is the most comprehensive and up-to-date coverage of the process of desalination in industrial and municipal applications, a technology that is becoming increasingly more important as more and more companies choose to “go green.”  This book covers all of the processes and equipment necessary to design, operate, and troubleshoot desalination systems, from the fundamental principles of desalination technology and membranes to the much more advanced engineering principles necessary for designing a desalination system.  Earlier chapters cover the basic principles, the economics of desalination, basic terms and definitions, and essential equipment. 

The book then goes into the thermal processes involved in desalination, such as various methods of evaporation, distillation, recompression, and multistage flash.  Following that is an exhaustive discussion of the membrane processes involved in desalination, such as reverse osmosis, forward osmosis, and electrodialysis.  Finally, the book concludes with a chapter on the future of these technologies and their place in industry and how they can be of use to society. 

This book is a must-have for anyone working in water, for engineers, technicians, scientists working in research and development, and operators.  It is also useful as a textbook for graduate classes studying industrial water applications.    

• Language: English
• Publisher: Wiley
• Release date: Apr 11, 2019
• ISBN: 9781119407898

Book preview

Preface

The world-wide demand for fresh water is growing exponentially, while the supply of readily-available fresh water is dwindling. Several diverse techniques have been implemented to try to meet the growing demand for fresh water, with variable degrees of success. One technique that has had great success and that continues to grow in application is desalination. Desalination encompasses a host of technologies such that clean water may be generated regardless of location, make-up source, and/or energy source.

This book explores numerous desalination technologies. Some of the technologies that are covered here are highly commercialized and are in extensive use today, while others are under development and may be commercially-viable tomorrow. This book also covers renewable energy sources (wind, geothermal, and solar) as alternatives to fossil-fuels to drive desalination technologies.

World-renowned experts have contributed to this book. The authors’ experience includes decades of work in their respective fields, and covers the gamut from academia to real-world practice. I thank the authors for contributing their time and sharing their expertise to help us explore the possibilities within the realm of desalination.

Chapter 1

Introduction to Desalination

Jane Kucera

Nalco Water/an Ecolab Company

Corresponding author: Jane Kucera ([e-mail])

Abstract

The availability of fresh water on the planet is finite, and natural fresh water makes up only about 0.5% entire water supply on Earth. This limited supply, coupled with the growing population of the Earth and the growing industrialization of many developing countries, is driving global fresh water stress and scarcity to the point where more fresh water must be found to meet future needs. Methods to find more fresh water include conservation and reduce/reuse/recycle of existing fresh water sources, moving fresh water from water-rich regions to water-poor regions, and creating fresh water from other sources, such as oceans and wastewater, using desalination. Of these methods, desalination has proven to be a very viable technique to meet current and future fresh water needs in many areas around the world.

This introductory chapter discusses the history of, and drivers for desalination, and also provides a framework for the detailed discussions about various desalination technologies and opportunities to use renewable energy sources to power the desalination technologies that are presented in this book.

Keywords: Desalination, water scarcity, thermal desalination, membrane desalination, reverse osmosis, renewable energy sources

1.1 Introduction

Desalination: from the root word desalt meaning to remove salt from [1]. By convention, the term desalination is defined as the process of removing dissolved solids, such as salts and minerals, from water [2]. Other terms that are sometimes used interchangeably with desalination are desalting and desalinization, although these terms have alternate meanings; desalting is conventionally used to mean removing salt from other more valuable products such as food, pharmaceuticals, and oil, while desalinization is used to mean removing salt from soil, such as by leaching [2].

The first practical use of desalination goes back to the sixteenth and seventeenth centuries, when sailors such as Sir Richard Hawkins reported that their men generated fresh water from seawater using shipboard distillation during their voyages [3]. The early twentieth century saw the first desalination facilities developed on the Island of Curaçao and in the Arabian Peninsula [3]. The research into and application of desalination gained momentum in the mid-twentieth century, and the last 30 years has witnessed exponential growth in the construction of desalination facilities.

One could ask the question, Why desalination? Desalination has become necessary for several reasons, the most compelling of which may be: 1) the increased demand for fresh water by population growth in arid climates and other geographies with limited access to high-quality, low-salinity water, and 2) the per capital increase in demand for fresh water due to industrialization and urbanization that out paces availability of high-quality water. Research and development over the last 50 years into desalination has resulted in advanced techniques that have made desalination more efficient and cost-effective. Desalination is, and will be in the future, a viable and even necessary technique for generating fresh water from water of relatively low quality. Thus, the title of this book, Desalination: Water from Water.

In this chapter, and in this entire book, we make the case for desalination as one of the major tools for meeting the fresh water needs of a growing and industrializing planet.

1.2 How Much Water is There?

The allocation of the world’s water is shown in Figure 1.1. About 97.5%, or 1338 million km³, of the world’s water is sea-water [3, 4]. Eighty percent of the remaining water is bound up as snow in permanent glaciers or as permafrost [4]. Hence, only 0.5% of the world’s water is readily available as low-salinity groundwater or in lakes or rivers for direct use by humans.

Figure shows the allocation of world’s water resources.

Figure 1.1 Allocation of the world’s water resources.

1.2.1 Global Water Availability

Some regions of the world are blessed with an abundance of fresh water. This includes areas with relatively low populations and easy access to surface waters, such as northern Russia, Scandinavia, central and southern coastal regions of South America, and northern North America (Canada, Alaska) [2, 5]. More populated areas and areas with repaid industrialization are experiencing more water stress, particularly when located in arid regions.

There are numerous methods to calculate water stress (e.g., The Faulkenmark Indicator [6]), and many maps that display current and projected future water stress. In most cases, water stress is measured by comparing the amount of water used to that which is readily available, as explained by Maplecroft:

"The Maplecroft Water Stress Index evaluates the ratio of total water use (sum of domestic, industrial, and agricultural demand) to renewable water supply, which is the available local runoff (precipitation less evaporation) as delivered through streams, rivers, and shallow groundwater. It does not include access to deep subterranean aquifers of water accumulated over centuries and millennia.

The application of the index is to provide a strategic overview of the current situation of physical water stress at global, continental, regional, and national levels. It does not take account [any] future projection, [or] water management policies, such as desalination, or the extent of water re-use" [5].

Figure 1.2 shows the baseline water stress for the world, as estimated by the World Resources Institute for 2015.

Figure shows the baseline stress for the world as estimated for 2015 by the World Resources Institute. It shows the areas which are not rich or insufficient in water resources.

Figure 1.2 Global baseline water stress, 2015. Courtesy of World Resources Institute.

The areas of the world that are not rich in water resources and that also experience un-stable and rapid population growth and industrialization will see water stress significantly increase in the future. Figure 1.3 compares the global water stress in 1995 with that predicted for 2025 [7]. As many as 2.8 billion people will face water stress or scarcity issues by 2025; by 2050, that number could reach 4 billion people [7] (See Figure 1.4 for world-wide 2040 estimates). Water stressed areas will include the south central United States, Eastern Europe, and Asia, while water scarcity (extremely limited access to flush water) will be experienced in the Southwestern United States; Northern, Southern, and Eastern Africa; the Middle East; and most of Asia [2].

Figure compares the global water stress in 1995 with that predicted for 2025. It marks the regions with water availabilty of more than 40%, from 40% to 20%, from 20% to 10% and regions with less than 10% of water both in 1995 and 2025.

Figure 1.3 Global water stress in 1995 and predicted for 2025. Courtesy of Philippe Rekacewicz (Le Monde diplomatique), February 2006.

Figure shows estimation of countrywise water stress for 2040 by the World Resources Institute.

Figure 1.4 Projected water stress by 2040. Courtesy of World Resources Institute.

1.2.2 Water Demand

The demand for water in developed nations is relatively high. Demand in the United States is about 400 liters per person per day [4]. Some Western countries that have been successful in implementing conservation and reuse measures have seen their demand for water drop to about 150 liters per person per day [4, 8]. However, the limited availability and access to water in some parts of the world, results in much lower consumption in these regions. For example, per capita freshwater consumption in Africa is only about 20 liters per day due to the shortage of suitable water [8]. The World Heath Organization (WHO) deems 15 to 20 liters per person per day is necessary for survival, while 50 liters per person per day is estimated to be needed for operation of basic infrastructure such as hospitals and schools (see Figure 1.5) [4]. The WHO estimates that by 2025, the worldwide demand for fresh water will exceed supply by 56% [8].

Figure shows the global demand in terms of basic needs for survival and infrastructure requirements of water in USA, Africa and western nations with conservation through a graphical representation.

Figure 1.5 Global demand for water and World Health Organization basic water requirements (2010).[4, 8].

In addition to population growth, another pressure being exerted on water supply is fact that the per capita water demand is increasing faster than the rate of population growth [9]. According to Global Water Intelligence [10], the per capital water demand has outpaced population growth by a factor of 2. By 2050, global water demand is expected to increase 55% over 2015 demands, primarly due to manufacturing, thermal electricity generation and domestic use [11].

1.2.3 Additional Water Stress Due to Climate Change

While population growth and per capita increase in demand are two major water stressors, the impact of climate change on global water stress cannot be ignored. The effects of climate change actually work synergistically with population growth and increasing demand to strain water supply. As population and industrialization grow, climate change accelerates, leading to more drastic climate events such as drought. A study by the National Center for Atmospheric Research (NCAR) indicates that severe drought is a real possibility for many populous countries [12]. Regions that are projected to experience considerable drought include most of Latin America, the Mediterranean regions, Southeast and Southwest Asia, Africa, the southwest United States, and Australia [9]. Coincidentally, many of these regions are also experiencing increases in population, industrialization and, urbanization, with the corresponding increase in per capita water demand. The United Nations forecasts that the world will have 27 cities with populations greater than 10 million by the year 2020, and all but 3, New York City, Moscow, and Paris, will be in regions under the threat of significant drought [9].

Risks to freshwater supplies increase with increasing greenhouse gas emissions (via industrialization). [11] For example, higher seawater levels due to melting of polar ice can lead to a variety of problems, including seawater intrusion into coastal aquifers and higher water temperatures, leading to faster dissolved oxygen depletion, both of which affect the quality of this fresh water source. [13].

The effects of climate change on water balance and availability, coupled with population growth and industrialization, will create added future challenges for finding more fresh water to meet demand.

1.3 Finding More Fresh Water

For much of the world’s urbanized population, fresh water is an afterthought, a commodity that has been easy to find and always there at the tap. However, water in some parts of the world is increasingly considered a product that must to be found and developed to meet growing demand. Depending on the specific circumstances in a particular geography, one or more methods may need to be implemented to find and develop water sources to meet future water needs. Some of these methods are summarized below.

1.3.1 Relocating Water

Moving water from water-rich areas to water-scarce regions, while sounding extreme, is not a new idea. Witness the diversion of water to the desert southwest United States for drinking, power, and irrigation uses. Los Angeles currently imports 85% of its water demand from outside sources: the Sierra Nevada Mountains, the Delta in Northern California, the Los Angeles Aqueduct, and the Colorado River Aqueduct [14].

However, moving water is not always palatable. Public outcry against moving water from a water-rich region can be a formidable obstacle. Consider the Columbia River in the Pacific Northwest United States. Water is Oregon’s Oil, declared Oregon State Senator David Nelson in his 2007 white paper, Columbia River Diversion as a Public Revenue Source. Diversion of the Columbia River to other western states has been a topic of discussion in the State of Oregon for over 40 years. Not much has come of this discussion to date however, as water-poor areas in the region have found other sources for water, and, more to the point, Oregonians have routinely declined to give up their supply of inexpensive fresh water that also serves as their source for relatively inexpensive hydroelectric power.

Politics can also play a role in how water supplies are dispersed. In the late 2000’s, different political parties in Spain were having a tug-of-war over how to supply the south-eastern area of Spain with water. The conservative party in Spain advocated moving water from the Ebro River (an eastern river whose delta into the Mediterranean Sea is about half way between Barcelona and Valencia) to the Community of Valencia, which lies approximately 200km from the delta. The Socialist Party in power has commissioned the Torrevieja Seawater Reverse Osmosis (SWRO) facility, the 6th largest SWRO facility in the world, which is located in Alicante, Municipality of Torrevieja, about 75 km from Valencia. Backers of the Ebro river project have denied a permit for concentrate discharge from the SWRO facility, thereby preventing the construction of the seawater intake and outfall pipelines [14]. The Terreveija facility was delayed for 3 years due in part to the political wrangling. Having been finally constructed, the facility is designed to deliver 240,000 m³/day to approximately 400,000 people (see Figure 1.6). The Valencia province has 2.5+ million people with several more SWRO projects under way that could encounter the same political stalemate.

Image shows a seawater reverse osmosis desalination facility in Terreveija, Spain which is designed to deliver 240,000 m3/day to approximately 400,000 people.

Figure 1.6 Terrevieja, Spain, 240,000 m³/day seawater reverse osmosis desalination facility. Courtesy and copyright of Acciona.

While importing fresh water makes sense in some cases, public and political pressures, as well as technical issues, such as moving water long distances, particularly when elevation changes are involved, will not make importing water supplies feasible or even possible to meet the requirements of all regions in need of fresh water.

1.3.2 Conservation and Reuse

Conservation is a term that has been used for decades to mean more efficient usage and savings of a resource, in this case, water. The twenty-first century equivalent terms for conservation are sustainability, and more recently green, and reduce/reuse/recycle. Regardless of which term is used, the need to conserve through more efficient usage, recycling, and reuse has become popular in today’s culture. While these techniques are oft times the first choice of populations located in arid areas or far from an ocean as a means of finding more fresh water, all populations can benefit from these techniques.

For example, consider the City of Los Angeles, California, an arid, coastal city that receives only about 40cm of rain a year. Los Angeles imported roughly 85% of its water from northern California, the Owens River, and the Colorado River as of 2013 (see Figure 1.7). Los Angeles is one large metropolitan area that has considered conservation to supply an increasing portion of its future water needs. Los Angeles Country has a current population of about 10.2 million people and is expected to grow to reach 26 million inhabitants by 2060 [16]; water demand is expect to rise by 123 million m³ per year [9, 17]. The Los Angeles Department of Water and Power (LADWP) describes the future of the city’s water philosophy: Conservation will continue to be a foundation of LADWP water resource management policy, and will be implemented to the fullest extent concurrent with further consideration of alternative water supplies [18].

Figure shows an aqueduct system delivering water to Los Angeles and the amount of water imported by them from northern California, the Owens River, and the Colorado River as of 2013.

Figure 1.7 Water sources for Los Angeles, California, USA [15].

In addition to its aggressive conservation plan, the LADWP has developed a new Recycled Water Master Plan which relies heavily on recycling highly-treated wastewater as a cost-effective solution to meet some of the future demands of the city [19]. The Edward C. Little Water Recycling Facility (ELWRF) located in the City of El Segundo, Los Angeles County, CA (commonly referred to as West Basin), is a model for water conservation, recycling, and reuse. The facility, funded in 1992 following the severe drought in California in the late 1980’s and early 1990’s, produced about 236,000 m³/d of recycled water in 2013 at a 2012 investment of $500 million [20]. Five grades of water, known as designer water, are produced by the facility to match the needs of local industry (water type listed roughly from lowest to highest quality):

Tertiary wastewater (known as Title 22 Water) for general industrial and irrigation uses, such as irrigating golf courses,

Nitrified water for use in industrial cooling towers,

Softened reverse osmosis (RO) water for ground water recharge,

RO water for low-pressure boiler feed water at local refineries, and

Ultra-pure RO water for high-pressure boiler feed water at local refineries.

The objective of the LADWP Recycled Water Master Plan is to recycle a total of about 62 million m³ of water per year by 2019 at an estimated cost of $715 million to $1 billion [14, 18]; by 2035, the goal is to recycle 72 million m³/year [22]. West Basin has already achieved 2/3 of that water recycling goal. The recycled water conserves 42 million m³/year of water that would have to be imported from elsewhere to meet demands [23].

Table 1.1 shows the water sourcing plan for the LADWP from actual sourcing in 2010 to projected sourcing in 2032. [15]. Conservation and recycling wastewater, using West Basin as the example in Southern California, will require treatment, such as desalination, to produce water that is suitable for reuse. Conservation and recycling has the potential to slow the rate at which new, future supplies of fresh water may need to be developed, but will not, by itself, meet the total local and worldwide need for fresh water.

Table 1.1 Actual and projected water sources for Los Angeles Department of Water and Power. Adapted from [15].

*Northern California’s Sacramento and San Joaquin Rivers, via the State Water Project, and the Colorado River, via the Colorado River Aqueduct, provide 45% of MWD water sources.[21]

1.3.3 Develop New Sources of Fresh Water

Developing new sources of fresh water other than traditional sources, such as lakes, rivers, or relatively shallow wells, is another method for meeting the demand for more fresh water. The most common new sources for developing new fresh water supplies are seawater and deep wells or saline aquifers, and waste water.

Seawater is the traditional source water when one thinks of desalination. Seawater represents the feed water source for the majority of desalination facilities in the world (59%) [24]. The majority of these facilities were developed in the Arabian Gulf region, Algeria, Australia, and Spain. In the united states seawater desalination is also being used to reduce the dependence of the Southern California Region on imported water. Southern California has a handful of direct seawater desalination facilities, the largest of which is the Claude Bud Lewis Carlsbad SWRO Desalination Facility near San Diego (see Figure 1.8). The facility was commissioned in December, 2015, and supplies 190,000 m3/day of fresh water to San Diego County. Another 190,000 m3/day facility is in later stages of installation in Huntington Beach, near Los Angeles. For sea-bounded, arid areas, turning to the sea for water is only natural, (see Figure 1.9 [25].

Figure shows the Claude “Bud” Lewis Carlsbad SWRO Desalination Facility near San Diego which is largest desalination facility in Southern California. It supplies 190,000 m3/day of fresh water to San Diego.

Figure 1.8 Claude Bud Lewis Carlsbad (California) Desalination Facility. Courtesy of Poseidon Water.

Figure shows country-wise percentages of seawater disalination through a pie diagram.

Figure 1.9 Seawater disalination by country 2015 [25].

However, seawater supply is only suitable as a desalination source for coastal areas; inland areas would need to rely on other sources, such as saline aquifers for new water supply. Figure 1.10 shows a United States Geological Survey (USGS) map of US saline aquifers; the map was generated in 1965 and was not updated until 2017 [26]. The 2017 USGS study, Brackish Groundwater in the United States, (Professional Paper 1833, published April, 2017) [27], looked at more than 380,000 sites (compared to 1,000 in the original, 1965 survey). This recent study generated a significantly more comprehensive view of the characteristics of US aquifers than the original survey (see Figure 1.11). The USGS found that groundwater in US aquifers is 800 times the volume of fresh water currently used in the US [26]. For California, desalinated groundwater could provide enough water to meet the state’s needs for 160 years [28]. While some applications don’t require high-quality water, such as mining, oil and gas development, and thermoelectric power generation, and can use the groundwater as is, other applications (including most industrial, municipal, microelectronic, and pharmaceutical) would require treatment of the groundwater via desalination prior to use [26]. The key to groundwater use is sustainability; the ability to recharge the aquifers in a reasonable time and manner [28]. Note that most current activity involving saline aquifers centers on using them as storage for greenhouse gases, primarily carbon dioxide, rather than as sources for fresh water [29]. This is presumably due to the need to treat the water to generate fresh water from the saline brines as opposed to the relative ease of injecting greenhouse gases, a process that does not require treatment, into the aquifers.

Figure shows a United States Geological Survey (USGS) map of US saline aquifers. The map was generated in 1965 and was not updated until 2017.

Figure 1.10 United States Geological Survey map of depth to saline ground water in United States aquifers, cir. 1965.

Figure shows the observed minimum depth of saline groundwater in US for 2017.

Figure 1.11 Observed minimum depth to brackish or highly-saline groundwater in the United States and Selected US Territories for 2017 Survey [USGS]. Courtesy of the U.S. Geological Survey, Professional Paper 1833, https://doi.org/10.3133/pp1833, April, 2017.

One arid area that is already desalinating aquifers to provide fresh water is the state of Texas in the united states as of March, 2016. Texas had more than 100 desalination facilities, all using brackish ground water as the feed source, although several seawater desalination facilities are planned. [30] While most Texas facilities are small or intermittent operation, the largest facility by far is the Kay Bailey Hutchinson facility in El Paso. This facility can generate approximately 104,000 m³/day. [30]

Another and perhaps more challenging feed source is wastewater. Industries and municipalities have wastewater that can be treated and reused for a variety of industrial applications. West Basin in Los Angeles is a good example of using desalination technologies, ion exchange softening and RO, to recover industrial–grade water from wastewater, as discussed previously. Wastewater from various industries, for example, power and refineries, each have their own characteristics, which typically must be treated before discharge. Adding a desalination step to the treatment can, in many cases, yield water suitable for reuse within the facility, thereby reducing the requirement for fresh water from natural sources.

Seawater and other sources present an opportunity to meet the growing water needs of the world. Table 1.2 lists generally-held classifications of water as a function of salinity (note that saline aquifers are generally considered to be at least moderately brackish and most wastewater are at least mildy brackish). Considering these classifications, even the higher-salinity fresh water would require treatment for potable or industrial use to reduce the concentration of dissolved minerals. Thus, desalination can be used to generate high-quality water from water that is, without treatment, not suitable for direct use.

Table 1.2 Classification of source waters as a function of total dissolved solids (TDS).

* World Health Organization [10].

1.4 Desalination: Water from Water

1.4.1 Drivers for Desalination

One can conclude from the discussions in this chapter that new sources of fresh water must be developed to meet the growth in the demand. Apart from moving water from location to location, reuse of wastewater and use of alternate sources of water will require treatment to yield water that is suitable for potable or industrial use. And, since wastewaters and alternate source waters are generally brackish or highly saline, desalination technologies will most certainly be required as part of the treatment scheme. Thus, the driver for desalination is clear: future demand for high quality water will require desalination of water sources that are lower in quality (higher in dissolved solids) than are commonly utilized today (and which may not be available tomorrow). [31]

Desalination of various water sources to provide a supply of fresh, usable water has been growing almost exponentially since 1965, when global commissioned desalination capacity was less than 2 million m³/d [32]. By June, 2016, the global commissioned desalination capacity was over 88 million m³/d [33]. Figure 1.12 shows the rate of increase in the cumulative, on-line capacity since 1965. [33] However, the incremental, new, on-line and contracted capacity has waned considerably from the peaks in the late 2000’s (see Figure 1.12). [33] The IDA Desalination Yearbook 2016–2017 explains that the downturn is due, at least in part, from … low commodity [oil] prices, and the dependence of certain regional economies on these prices, helping to cancel out some of the increasing demand from factors such as population growth, increased industrialization, drought and climate factors, and competition for water resources. [33]

Figure contains 2 graphs describing the cumulative as well as new, on-line desalination capacity from 1965 till 2016. The on-line capacity has increased in the cumulative since 1965 whereas the capacity has waned considerably from the peaks in the 2000s.

Figure 1.12 Growth of cummulative (a) and new (b), on-line desalination capacity. Courtesy of Global Water Intelligence.

1.4.2 Feed Water Sources for Desalination

Feed water sources for desalination are varied. As previously discussed, feed sources can range from seawater and saline aquifers to wastewater for recycle and reuse. While seawater represents the feed water source for the majority of desalination facilities, the use of other feed water sources, such as brackish water, saline aquifers, and wastewater, has been growing steadily since 2000 [33]. Figure 1.13 shows the growth in annual new contract capacity by feed water type through June, 2016. [33] As the figure shows, the downturn in incremental capacity shown in Figure 1.10 is primarily due to the decrease in demand for seawater desalination plants, particularly in the Middle East and North Africa.[33] Brackish water and other sources showed volatility but continued to show modest increases through June, 2016.

Figure shows the growth in annual new contract capacity by feed water type through June, 2016. It has 3 waves each for seawater, brackish and others

Figure 1.13 Annual new contracted desalination capacity by feed water type [33]. Courtesy of Global Water Intelligence.

Figures 1.14 shows more detail in the total worldwide install capacity by feed water type through August, 2012. [25, 37]

The pie chart shows the total worldwide capacity by feed water through August 2012. The type of feedwater involves seawater, brackish, river, waste and pure water.

Figure 1.14 Total, global installed capacity by feed water source as of 2012 [37]. Courtesy of Global Water Intelligence.

Although feed sources for desalination appear to be limited in number, (e.g. seawater, brackish water saline aquifers, and wastewater) composition of specific examples of the various make-up source classifications can differ greatly depending on their hydrologic origin. Table 1.3 demonstrates some of the variability in well and surface waters, with a standard seawater and a sample grey water source included for comparison (the well, river, and grey waters shown in Table 1.3 either are currently being used as feed water sources for desalination facilities or have been considered for use as source water for such facilities) [3].

Table 1.3 Sample water composition of seawater, well water, surface water, and grey water sources.

NA = Not available

aReferences 3, 4, and 8

bEl Paso Water Utilitites, El Paso Airport Wells [3]

cWater from Benson, Arizona, Kevin O’Leary, Aquatech, personal communication, April 7, 2008

dColorado River Water near Andrade, CO [3]

eWater from Chicago, Illinois, Anne Arza, Nalco Water, an Ecolab Company, personal communication, May 16, 2011

fHotel hygiene wastewater, Las Vegas, Nevada, August 21, 2007

Despite variations in quality among the various feed water sources, they all share the characteristic of being relatively high in salinity or total dissolved solids (TDS). High salinity (and, in some cases, other mineral constituents) makes the water unsuitable for direct potable and industrial use. Therefore, demineralization or desalination treatment to reduce the concentration of TDS must be part of the treatment system employed if these sources are to be used to supplement or replace existing fresh water supplies.

1.4.3 Current Users of Desalinated Water

The primary user for desalinated water is the municipal sector; sixty percent of desalinated water is used for potable application. [35] Industrial and power users together accept another third of the worldwide desalination capacity (see Figure 1.15) [35]. Although potable applications account for nearly twice the total volume of desalinated water used than industrial applications, the number of industrial facilities (including power) out numbered municipal facilities by almost 2 to 1 (8,715 to 4,415 respectively) in 2011, indicating that the size of industrial desalination facilities are considerably smaller than municipal facilities [18]. The remaining 6% of desalinated water is used for irrigation, tourism, military, and other applications [35].

Figure shows the total 2015 global installed capacity by municipal, industry, power, irrigation, tourism, military and others with the primary user being municipal.

Figure 1.15 Total, 2015 global installed capacity by type of user [35]. Courtesy of Global Water Intelligence.

1.4.4 Overview of Desalination Technologies

The world-wide installed desalination capacity in 2016 was about 86.5 million m³/d [24]. Figure 1.16 shows the relative breakdown of installed capacity of various desalination technologies for 2010(a) and 2016(b) [24, 32].

Figure shows 2 pie charts one for 2010 and another for 2016 depicting the relative breakdown of installed capacity of various desalination technologies.

Figure 1.16 Global installed desalination capacity by technology for 2010(a) and 2016(b) [24, 32]. Courtesy of Global Water Intelligence.

Membranes are currently outpacing traditional thermal technologies in total installed desalination capacity. Prior to 1980, membrane technologies made up less than a third of the global desalination capacity [19], while today, membranes account for just roughly 2/3 of the total installed desalination capacity [24]. As shown in Figure 1.16, installed capacity of RO grew from 60% of total installed capacity in 2010 to 65% in 2015, an increase of 8% over the year, while installed capacity of thermal, multi-stage flash (MSF) evaporation decreased by over 21% for the same period; installed capacity of thermal, multi-effect distillation (MED) declined slightly from 8% to 7% remained steady at 8%. Membrane technologies such as RO offer the advantage of smaller infrastructure, and RO total treated water cost is becoming competitive with traditional thermal processes [36].

Membrane-based systems are popular in rising markets such as Algeria, Spain, and Australia, while thermal processes are found in traditional markets such as the Middle East, where energy costs are lower [32]. The proportion membrane-based desalination has been growing, as shown in Figure 1.17; globally, new membrane capacity was 93% of total new desalination capacity from 2015 through June, 2016. [33].

The graph shows the growth of installed proportion membrane and thermal desalination capacity through from 1980 to 2015 by Courtesy of Global Water Intelligence.

Figure 1.17 Growth of installed membrane and thermal desalination capacity. Courtesy of Global Water Intelligence.

Top countries by total installed thermal capacity from 1945–2012 include (approximate, in million m³/d): [37]

United Arab Emirates (UAE): 7.3

Saudi Arabia: 5.9

Kuwait: 2.3

Qatar: 1.3

Libya: 0.9

Top countries by total installed membrane capacity from 1945–2012 include (approximate, in million m³/d): [37]

United States: 7.9

Saudi Arabia: 5.1

Spain: 4.6

China: 2.0

UAE: 1.5

The global trend toward membrane systems, primarily SWRO, over traditional thermal processes is driven by a several factors, including [33]:

Lower RO capital costs due to less-expensive construction materials;

Versatility in RO feed sources (MSF and MED are impractical for all but sweater desalination);

No thermal energy requirement for RO, while MSF and MED desalination are cost-effective in areas with subsidized energy or in conjunction with an industrial process, such as power generation that yields inexpensive, low-pressure steam.

Growth of membrane technology over thermal processes has occurred even in the traditional thermal markets. In the years 2000–2009, the portion of new membrane capacity in the Middle East and North Africa (MENA) was 55% as compared to 45% for thermal capacity; during 2010–2014, new membrane capacity increased to 76% of new, installed capacity; and in in the period of 2015 through June, 2016, new, membrane capacity had increased to 86% of the total new capacity. [33]

While thermal plants still predominate in the Middle East, due to easy access to fossil fuel resources (relatively inexpensive energy), the relatively poor seawater quality (high salinity (up to 55,000 ppm TDS)) in the Gulf Region that limits RO recovery, and high the temperature of the seawater, which promotes biofouling of the membranes, has made the water in this region not well suited for previous generations of SWRO [38]). However, as pretreatment and membrane materials have improved (e.g., higher permeability and salt-rejecting membranes that operate at lower pressure), SWRO has become viable in the Middle East. Energy-recovery devices now used with SWRO also reduce the mechanical energy requirements of the process [39, 58]. Further, energy initiatives in the region, such as the Dubai Clean Energy Strategy 2050, currently drive new desalination capacity in the region toward SWRO [41].

New membrane capacity in the region is typically in the form of hybrid MSF/SWRO facilities. The largest desalination facility in the world, Ras Al Khair Desalination Plant, in Saudi Arabia employs both MSF and RO to generate 1.025 million m³/day of water (the facility is co-located with a 2,650 MW combined cycle power plant—see Figure 1.18). The 8 MSF units and 17 RO units generate 727,000 m³/day and 309,000 m³/day, respectively, of fresh water. The Jebel Ali desalination facility in Dubai, UAE, which also co-located with a power station (see Figure 1.19) currently generates 636,000 m³/day of fresh water using 8 USF units, but is looking to expand capacity by 182,000 m³/day using SWRO. Dubai Electricity and Water Authority (DEWA) chose RO for the expansion due to its lower-energy requirements. [41] Indeed, many thermal plants in the region are expanding capacity using SWRO.

Figure shows the Ras Al Khair desalination facility in Saudi Arabia which generates 1.025 million m3/day of fresh water.

Figure 1.18 The Ras Al Khair desalination and power generating facility in Saudi Arabia. The desalination facility generates 1.025 million m³/day of fresh water using MSF and SWRO.

Figure shows the Jebel Ali MSF desalination plant and power complex in Dubai.

Figure 1.19 The 636,000 m³/day Jebel Ali MSF desalination plant and power complex in Dubai, UAE. Expansion of the desalination plant will use SWRO.

1.4.5 History of Desalination Technologies

Desalination has grown substantially since the mid 1960s. In 1952, there were only about 225 desalination facilities world-wide with a total capacity of about 100,000 m³/d. [2] In 2015 there were over 15,000 desalination facilities globally [32] and in 2016, the total global capacity was over 86 million m³/d; 44% of this capacity was located in the Middle East and North Africa [24, 31].

While there are many desalination technologies in use or being developed today, desalination began using thermal processes. Membrane-based processes, such as RO, helped to further promote desalination over the last 50 years. The history of these pioneering technologies is outlined below.

1.4.5.1 History of Thermal Desalination

Thermal desalination techniques were recognized as early as 320 B.C. when Aristotle wrote, ‘saltwater, when it turns into vapor, becomes sweet and the vapor does not form saltwater again when it condenses.’ Shipboard distillation beginning in the sixteenth century is the first practical use of distillation to generate fresh water from seawater [42]. In 1843, Rillieux successfully patented, built, and sold multi-effect evaporators [42].

The number of thermal desalination installations has grown rapidly over the last 100 years. However, while RO and other membrane technologies were revolutionary in development, the development of thermal desalination technologies over the last 45 years has been more evolutionary than revolutionary [43].

Multi-effect distillation was the first thermal desalination technology employed [42, 43]. The first units were designed with submerged tube evaporators the exhibited low heat transfer rates and high scaling rates. Vertical- and horizontal-tube evaporators (also known as falling-film evaporators) used in modern MED facilities provide higher heat transfer coefficients and lower specific heat transfer surface area requirements than their older counterparts. Drawbacks of the current MED technology are the complexity and production capacities [43]. Also, the relatively low, maximum-brine temperature of MED (~65 °C) due to scale-forming issues, is another limitation of MED. However, the use of membrane pretreatment such as nanofiltration (NF) prior to MED to remove the calcium that contributes to calcium-sulfate scale in MED units has been considered as a way of allowing higher temperature operation of MED and, thereby enhance the use of MED for desalination [43].

Due to the early issues with MED (e.g., scaling and low heat transfer rates), MSF distillation technology was developed in the late 1950s and early 1960s as an alternative. Flashing distillation was first commercially employed by Westinghouse in Kuwait in 1957 [42]. That same year, an MSF distillation patent was issued; in 1959/60, the first commercial MSF facilities were installed in Kuwait (19 stages, 4550 m³/d) and the Channel Islands (40 stages, 2775 m³/d) [44, 45]. In 1973, standard MSF units, that produce justover 27,000 m³/day and consisted of 24 stages, were developed [42]. In 1984, the Doha West Power and Desalination plant came on line in Kuwait City, Kuwait, with a desalination capacity of 110,000 m³/day using 4 MSF units (27,500 m³/day each), see Figure 1.20. This currently, the desalination plant is being augmented with 140,000 m³/day of SWRO capacity (see discussion of hybrid desalination facilities in Section 1.4.4.).

Figure shows the Doha West Power and Desalination plant in Kuwait City, Kuwait, with a desalination capacity of 110,000 m3 /day using 4 MSF units.

Figure 1.20 MSF Desalination plant (110,000 m3/day capacity) combined with power plant - Doha West, Kuwait. Courtesy of MEW (Ministry of Electricity and Water).

Recent developments in the thermal desalination technology have focused on scale and corrosion control techniques and on the increase in distiller production capacity [43]. Early, pre 1980, MSF units were primarily constructed using carbon steel for the shell and the internals [46]. Corrosion of the metal due to seawater resulted in the use of thicker materials of construction, which made the units larger and heavier. Units built after 1980 use stainless and duplex stainless steel to reduce corrosion, allowing for lighter and smaller MSF units. Future advances in the technology will most likely focus on improvements in thermodynamics and material selection [46].

1.4.5.2 History of Reverse Osmosis Desalination

While the earliest recognition of thermal desalination was a few hundred years B.C., the earliest recorded documentation of semi-permeable membranes was in 1748, when the phenomenon of osmosis was observed by Jean-Antoine Abbe Nollet [47]. Osmotic phenomenon was also studied in the 1850’s, and then in the 1940’s, when Dr. Gerald Hassler began investigation of the osmotic properties of cellophane [48]. Modern RO technology truly began in the late 1950’s when C.E. Reid and E.J. Breton at the University of Florida and Sidney Loeb and Srinivasa Sourirajan (working under prof. Samuel Yuster) at the University of California at Los Angeles (UCLA) independently demonstrated RO using polymeric membranes. Figures 1.21 and 1.22 show Sidney Loeb and the Big Dripper flat-sheet, cellulose acetate membrane he developed.

There are 2 images with one picture of Sidney Leob and another picture of coworkers both with Loeb’s “Big Dripper” flat sheet membrane machine.

Figure 1.21 Sidney Loeb (a and b) and coworker (b) with Loeb’s Big Dripper flat sheet membrane machine. Courtesy of Julius Glater.

Figure shows the UCLA team of 4 men at Rain Tree facility, Coalinga, California.

Figure 1.22 UCLA Team at Rain Tree facility, Coalinga, California, USA. Courtesy of Julius Glater.

The United States was the early leader in desalination research in the 1960s and 70s due in most part to government funding. The Saline Water Conversion Act of 1952 established the Office of Saline Water (OSW) in 1955, which later became the Office of Water Research and Technology (OWRT) in 1974. It was under such governmental programs that Loeb and Sourirajan developed the first commercially-viable RO membrane while at the UCLA [48]. In 1965, the tubular, cellulose acetate membrane developed at UCLA became the membrane used in the first commercial RO facility located in Coalinga, California [49]. Figure 1.22 shows UCLA team at the Coalinga facility.

Government funding also lead to the development in 1965 of the solution/diffusion membrane transport model by Harry Lonsdale, U. Merten, and Robert Riley at the General Atomic Division of General Dynamics, Corp [50]. This model has become the basis of research and development of new membrane materials since that time. [51]

It was under similarly-funded governmental programs that John Cadotte, while at North Star Research, prepared the first interfacial polyamide membrane US patent US 454,039,440, issued August 7, 1977, and later while at Filmtec corporation, the US patent US 4,277,344, issued July 7, 1981, and commonly referred to as the Cadotle 344 patent, that soon after became the basis of the FilmTec FT30 membrane (now part of DowDupont) [52]. The original FT30 membrane chemistry is the basis of the majority of reverse osmosis membranes in use today [44].

The OWRT was abolished in 1982 and government funding of desalination research in the United States dropped considerably. By that time, however, much of the foundation for RO, membrane-based desalination had been laid. Since then, incremental membrane improvements have been made in the areas of flux, rejection, and operating pressure requirements, as shown in Table 1.14 [45]. However, no major breakthroughs in terms of higher membrane selectivity with higher water flux and chlorine tolerance have occurred in 45+ years since the revolutionary early developments. Research is continuing, however, and the development of nanotechnology and nanocomposite membranes circ. 2005 has raised hopes that RO membranes with higher selectivity, water flux, and chlorine tolerance may be on the horizon, all of which would reduce costs and improve efficiency associated with membrane desalination [44].

1.4.5.3 Developments in Desalination Since 1980

Since 1980, the world-wide development of desalination techniques has been driven out of necessity due to water scarcity and population growth. The private sector has led the investment in research and development as they began to see water not as a commodity, but as a product to be sold at a profit [3]. This development by the private-sector has lead to a significant drop in cost of water generated through desalination techniques. An example of such is the 80% reduction in price of RO membrane elements over the last 30 years, while incremental improvements in flux, selectivity, and operating pressure were realized (Tables 1.4 and 1.5 [43, 52]). In 1991, the cost to produce water at the SWRO Charles E. Meyer Santa Barbara desalination facility was about 2.00/m³; in 2007, the estimated cost had dropped to about 0.89/m³ [2, 46, 56] (The facility was developed in the wake of the severe drought of the late 1980’s, and operated from March to June, 1992. However, sufficient water supplies since 1991, caused the facility to go into long-term, standby mode. The plant was reactivated in 2015, again due to severe drought conditions, and became operational in May, 2017. The reactivated facility will produce 11.4 m³/day using 40% less energy than the original design, due to retrofitting the facility with more efficient pumps/motors and membranes. [53]. Figure 1.23 shows the general cost range of desalinated water for MSF(a) and RO(b) (variability in cost is due to factors such as size of plant, degree of pretreat-ment employed and makeup source in the case of RO) [34, 39]. By comparison, direct municipal water from easily accessable wells and surface sources cost about $0.40/m³ in 2012 [54].

Table 1.4 Advances in brackish water reverse osmosis membrane performance [45].

* Hydranautic CPA7

Table 1.5 Decline in membrane cost relative to 1980 [55].

There are 2 graphs showing general cost range of desalinated water for MSF (a) and RO (b) processes. RO process costs vary with source water and generally show higher costs for seawater and wastewater, followed by river water and brackish water at the lower cost range.

Figure 1.23 Cost distribution reduction as a function of time for MSF (a) and RO (b) processes. RO process costs vary with source water TDS, and generally show higher costs for seawater and wastewater, followed by river water and brackish water at the lower cost range [34]. Courtesy of Elsevier.

There have been other desalination techniques invarious stages of development, some commercially successful, but none more commercially successful than traditional thermal and RO desalination processes. Table 1.6 lists a selection of desalination technologies and their current status.

Table 1.6 Sample desalination technologies. Technologies covered in this volume are noted in italics.

1.4.6 The Future of Desalination

Desalination today is still a capital and energy-intensive proposition. Methods to reduce costs are necessary to make the desalinated water more affordable. To that end, developments to increase the efficiency (and reduce costs of desalination) are needed. (Note that while some predictions call for a reduction of desalinated water costs of over 50% within 20 years [31], others predict that, while operating efficiencies will improve, little, if any, decrease in the costs for desalinated water will be realized [35]; instead, an increase in conventional water treatment and water importation costs is projected [35], which may help offset the cost of desalination.)

As of 2014, there were at least 5 national research initiatives underway, and over 50 active universities with desalination-related research & development (R&D) programs, plus hundreds of private sector R&D project ongoing [35].

Some areas of current development include:

Energy: There has been considerable reduction in the energy required to drive SWRO desalination plants, (Figure 1.24), due to improvements in membrane permeability and energy-efficient pumps, and the use of energy-recovery devices. [40]. In 2008, a pilot-scale SWRO system demonstrated desalination at 1.8 kWh/m³ [66] using high-permeability seawater elements. Work by the Desalination Coalition in 2006 [67, 68] demonstrated seawater desalination of 1.58 kWh/m3 under very ideal conditions, e.g., new membranes, no fouling, low flux, and 42% recovery.[69] These two examples include energy only for desalination, excluding energy for plant intake, pretreatment, post treatment, and brine discharge. Current SWRO plants in operation consume about 2.5–3.5 kWh/m³ [70]. In 2016, the Perth, Australia SWRO plant used 3.5 kWh/m³ of produced water (including total energy, from intake to customer), using wind energy and advanced energy recovery systems. [70] However, it is projected that the likelihood of any major, future improvements in in organic energy efficiency of SWRO is small [35].

The theoretical energy required to recover 50% of 35,000 ppm TDS seawater (by any desalination method) is 1.06 kWh/m3, and assumes a reversible thermodynamic process. [40]. In actuality, energy consumption will be higher since desalination plants do not operate as a reversible thermodynamic process [40].

Renewable energy to drive desalination projects, such as wind, solar, and geothrmal of are being considered to reduce the energy footprint also of desalination (today’s contribution of renewable energy sources to desalination processes is only about 0.05%) [71]. Table 1.7 shows some of the renewable energy sources (RES) currently considered to power desalination processes. Table 1.8 lists key data for RES and CO2-free desalination [72].

Materials: materials of construction for thermal processes that resist corrosion and reduce the size and weight (and costs) of units need to be developed. New membrane materials that resist attack by chlorine and fouling with microbes and that also show higher selectivity and higher flux are projected to be developed [31, 35]. Higher premeability will lead to lower energy costs for RO operations as discussed above. Although the development of new membrane materials, including nanocomposites, carbon nanotubes, aquaporins, and graphene, will continue, it is projected that these will not replace conventional, thin-film composite membranes for all but niche applications (e.g., high-purity or polishing). [35].

Chemicals: antiscalants for both thermal and membrane-based desalination processes to increase the degree of water recovery per given unit size, while reducing the potential for scaling.

Optimization: as energy costs will no doubt increase in the future, it is important that desalination plants are efficiently designed and operated as close as possible to the limits of performance of components, such as the RO membranes. [35]

The graph shows the change in power consumption for RO processes from year 1970 to 2008 with power consumption on y-axis and year on x-axis.

Figure 1.24 The change in power consumption for RO in SWRO plants from the 1970s to 2008. The horizontal dashed line corresponds to the theoretical minimum energy required for desalination of 35,000 ppm seawater at 50% recovery (1.06 kWh/m3). The energy data exclude the energy required for intake, pretreatment, posttreatment, and brine discharge. [65]

Table 1.7 Renewable energy sources (RES) and CO2-free technologies used to replace traditional fossil-fuel based energy sources to drive traditional desalination processes. These play a relatively small role in desalination today [71], but given the concerns regarding fossil fuels (e.g., availability, carbon footprint (see Table 1.9)), these sources show potential for future application in powering desalination. Solar, wind and geothermal energies are covered in this volume.

Table 1.8 Key data for renewable energy desalination, 2013 [72].

*membrane distillation

**photovoltaic

‡electrodialysis

‡‡brackish water

‡‡‡seawater

Table 1.9 Cir. 2010 airborne emissions per cubic meter of water generated by various desalination technologies when powered by fossil fuels and/or waste heat [71].

Despite thise development areas, no major breakthroughs are expected over the several years to radically lower the cost of desalination; instead, improvements in technologies will lead to slow but steady improvements. [31, 55]

Current desalination techniques can also have a significant impact on the environment, as described below [71]. Before desalination can become sustainable, these environmental issues must be addressed. The two most pressing issues are concentrate disposal and airborne emissions:

Concentrate disposal—very high salinity wastewater is generated through thermal and RO membrane desalination. Total dissolved solids can be as high 100,000 ppm in the wastewater from the desalination of seawater. Furthermore, concentrate can be highly turbid and be at elevated temperatures (thermal desalination plants), and can contain chemical additives such as polymers/coagulants, acid, biocides, corrosion inhibitors, and cleaners. The issue becomes how to dispose of the wastewater in an environmentally-safe manner that is also cost effective. Seawater desalination facilities currently discharge to the ocean, which some argue is damaging to local flora and fauna via increases in sea-water temperature, salinity, and turbidity. These conditions may be harmful to marine life and cause them to migrate away, and, at the same time, enhancing the populations of algae and nematodes.[78, 79] Inland brackish water facilities use other disposal methods, including discharge to surface water (45%), discharge to sewer (27%), deep well injection (16%), land application (8%), and discharge to evaporation ponds (4%) [79]. Each of these disposal methods has its own environmental concerns that are directly related to the high salinity and other characteristics of the water to be discharged.

Carbon footprint and airborne emissions—Table 1.9 lists airborne emissions for fossil fuel-powered desalination technologies. The carbon dioxide emissions from thermal desalination processes are a full order of magnitude higher than that for RO, when powered by fossil fuels. And, the energy to power the desalination facilities has the largest impact on the carbon footprint of the process [80]. The emissions for desalination technologies can be reduced significantly when these processes are powered by waste heat or RES such as solar radiation rather than by fossil fuels as shown in Tables 1.8 and 1.10 [71].

Table 1.10 Emissions for desalination processes powered by RES [82].

*100 kWp (peak power output)

NA = not applicable

Future demand for fresh water has led to a total desalination market value of 12.8 billion in 2015 [25] and will likely result in an estimated $19.9 billion expenditure on global desalination projects in the year 2020 [25]. Figure 1.25 shows the actual and projected market overview from 2000 to 2030. [25] Total, installed capacity in June, 2015 was 86.8 billion m3/d; project installed capacity for 2030 is over $50 billion. It is apparent that RO will be the primary mode of desalination for the foreseeable future, [33], Figure 1.14 [24] demonstrates the relative growth of RO to traditional thermal processes. Thermal processes, while in decline, still have a foothold, primarily in the Gulf Region Particularly where cogeneration with power yields low-cost steam. [24]

The graph shows the shows the actual and projected market overview from 2000 to 2030. It shows the annual and cumulative global desalination capacity as a function of time.

Figure 1.25 Annual and cumulative global desalination capacity as a function of time as calculated and projected by Global Water Intelligence and DesalData.com. Courtesy of Tom Pankratz.

While desalination plays a vital role in the sustenance and growth in many arid and water-poor areas of the world, there are still barriers to more widespread implementation, particularly for seawater desalination.

For desalination to be a sustainable method to develop sources of fresh water in the future, desalination technologies need to be economically and energy efficient and have a low environmental impact. Indeed, concerted efforts on these fronts have resulted in significant advances in desalination [81], which are described in this book:

improvements in performance and design of traditional technologies,

development of innovative new technologies,

the marriage of desalination technologies with RES.

1.5 Desalination: Water from Water Outline

In this volume we present the case for desalination, describe conventional and innovative new desalination technologies, present RES options for desalination, and conclude with a discussion of future directions.

In addition to conventional desalination technologies discussed in Section I (thermal and RO), there are many other technologies under development, as listed in Table 1.6. Current and several of the more promising desalination technologies under development are discussed in Sections II through IV of this book:

Section II: this section covers traditional thermal desalination technologies, including MED, and MSF. These technologies are very mature, but do have limitations that may be overcome with through future development of new materials to improve corrosion resistance and heat transfer, and through the development of antiscalants.

Section III: this section describes several membrane-based technologies, including RO, continuous electrodeionization, and membrane distillation, as well as some membrane-based desalination technologies that have only recently been commercialized, namely forward osmosis. Significant research