The state of desalination and brine production: A global outlook
, Manzoor Qadir
, Vladimir Smakhtin
, Seong-mu Kang
United Nations University: Institute for Water, Environment and Health (UNU-INWEH), Canada
Water Systems and Global Change, Wageningen University, the Netherlands
Gwangju Institute of Science and Technology (GIST), South Korea
•Unconventional water resources are key
to support SDG 6 achievement.
•Desalinated water production is
95.37 million m
•Brine production and energy consump-
tion are key barriers to desalination ex-
•Brine production is 141.5 million m
50% greater than previous estimates.
•Innovation and developments in brine
management and disposal options are
Received 31 August 2018
Received in revised form 5 December 2018
Accepted 5 December 2018
Available online 07 December 2018
Editor: Ashantha Goonetilleke
Rising water demands and diminishing water supplies are exacerbating water scarcity in most world regions.
Conventional approaches relying on rainfall and river runoff in water scarce areas are no longer sufﬁcient to
meet human demands. Unconventional water resources, such as desalinated water, are expected to play a key
role in narrowing the water demand-supply gap. Our synthesis of desalination data suggests that there are
15,906 operational desalination plants producing around 95 million m
/day of desalinated water for human
use, of which 48% is produced in the Middle East and North Africa region. A major challenge associated with de-
salination technologies is the production of a typically hypersaline concentrate (termed ‘brine’) dischargethat re-
quires disposal, which is both costly and associated with negative environmental impacts. Our estimates reveal
brine production to be around 142 million m
/day, approximately 50% greater than previous quantiﬁcations.
Brine production in Saudi Arabia, UAE, Kuwait and Qatar accounts for 55% of the total global share. Improved
brine management strategies are required to limit the negative environmental impacts and reduce theeconomic
cost of disposal, thereby stimulating further developments in desalination facilities to safeguard water supplies
for current and future generations.
© 2018 Elsevier B.V. All rights reserved.
Science of the Total Environment 657 (2019) 1343–1356
E-mail address: Manzoor.Qadir@unu.edu (M. Qadir).
0048-9697/© 2018 Elsevier B.V. All rights reserved.
Contents lists available at ScienceDirect
Science of the Total Environment
journal homepage: www.elsevier.com/locate/scitotenv
1. Introduction............................................................. 1344
2. Methodology............................................................. 1345
2.1. Globalstatusofdesalination:researchandpractice ........................................ 1345
2.1.1. Desalinationinresearch................................................. 1345
2.1.2. Desalinationinpractice................................................. 1345
2.2. Brineproduction........................................................ 1345
3. Results................................................................ 1346
3.1. Researchtrendsindesalination................................................. 1346
3.2. Globalstateofdesalination................................................... 1346
3.3. Brineproduction........................................................ 1349
4. Discussion.............................................................. 1352
5. Conclusions&outlook......................................................... 1354
Acknowledgements ............................................................ 1355
AppendixA. Supplementaryinformation.................................................. 1355
Rising water demands associated with population growth, increased
water consumption per capita and economic growth, coupled with
diminishing water supplies due to climate change and contamination,
are exacerbating water scarcity in most world regions (Richter et al.,
2013;Djuma et al., 2016;Damania et al., 2017). Recent estimates suggest
that 40% of the global population faces severe water scarcity, rising to 60%
by 2025 (Schewe et al., 2014). Furthermore, 66% of the global population
(4 billion) currently lives in conditions of severe water scarcity for at least
one month per year (Mekonnen and Hoekstra, 2016). These statistics
demonstrate that “conventional”sources of water such as rainfall, snow-
melt and river runoff captured in lakes, rivers, and aquifers are no longer
sufﬁcient to meet human demands in water-scarce areas. This is in direct
conﬂict with Sustainable Development Goal (SDG) 6, aimed at ensuring
the availability of clean water for current and future generations.
Water-scarce countries and communities need a radical re-think of
water res ource planning a nd management th at includes the c reative ex-
ploitation of a growing set of viable but unconventional water resources
for sector water uses, livelihoods, ecosystems, climate change adapta-
tion, and sustainable development (Qadir, 2018). Whilst water demand
mitigation approaches such as water conservation and improved efﬁ-
ciencies can somewhat close the water demand and supply gap, these
approaches must be combined with supply enhancement strategies in
order to combat water scarcity (Gude, 2017). Such water resources con-
servation and supply enhancement strategies are already practiced in
some water-scarce areas. However, expansion is required, particularly
in areas where water scarcity and water quality deterioration is intensi-
fying (van Vliet et al., 2017;Jones and van Vliet, 2018).
Among the water supply enhancement options, desalination of sea-
water and highly brackish water has received the most consideration
and is increasingly seen as a viable option to meet primarily domestic
and municipal needs. Desalination is the process of removing salts
from water to produce water that meets the quality (salinity) require-
ments of different human uses (Darre and Toor, 2018). Seawater desa-
lination can extend water supplies beyond what is available from the
hydrological cycle, providing an “unlimited”, climate-independent and
steady supply of high-quality water (Elimelech and Phillip, 2011).
Brackish surface and groundwater desalination offers reductions in the
salinity levels of existing terrestrial freshwater resources below sectoral
thresholds (Gude, 2017).
The uptake of desalination has been substantial, butlimited predom-
inantly to high income countries (e.g. Saudi Arabia, UAE, Kuwait) and
small island nations (e.g. Malta, Cyprus) with highly limited ‘conven-
tional’water resources (e.g. rainfall, snowmelt). However, reductions
in the economic cost of desalination associated with technological
advances, coupled with rising costs and the diminishing supply and se-
curity of “conventional”water resources, have made desalination a cost-
competitive and attractive water resources management option around
the globe (Ghaffour et al., 2013;Sood and Smakhtin, 2014;Caldera and
Breyer, 2017;Darre and Toor, 2018). Nowadays, an estimated 15,906
desalination plants are currently operational, located in 177 countries
and territories across all major world regions.
Realising the vast potential of desalinated water remains a challenge
due to speciﬁc barriers, predominantly associated with the relatively
high economic costs and a variety of environmental concerns (e.g.
Einav et al., 2002;Roberts et al., 2010;Richter et al., 2013;Darre and
Toor, 2018). Continued improvements in membrane technologies, en-
ergy recovery systems and coupling desalination plants with renewable
energy sources provide opportunities for reducing the economic costs of
desalination (Elimelech and Phillip, 2011;Pinto and Marques, 2017;
Darre and Toor, 2018), whilst trends towards stricter environmental
guidelines and permitting factors may cause the falling trend in desalina-
tion costs to slow, level off or reverse (Pinto and Marques, 2017). Regard-
less, continued reductions in the economic costs of desalination will be
required for desalination to be considered a viable option for addressing
SDG 6 in low income countries. Detailed evaluations of the challenges
and opportunities associated with the economics of desalination are pro-
vided by Ghaffour et al. (2013) and Pinto and Marques (2017).
The safe disposal of efﬂuent produced in the desalination process
remains a particular concern and a major technical and economic
challenge (Roberts et al., 2010). The desalination process separates
intake water into two different streams –a freshwater stream (product
water) anda concentrate waste stream (Wentenet al., 2017). The salin-
ity of the concentrate stream depends on the salinity of the feedwater.
As the vast majority of concentrate is produced from saline water
(N95% from SW and BW sources), the term ‘brine’is used throughout
this paper. However, it should be noted that desalination plants operat-
ing with low saline feedwater types (e.g. RW, FW) produce concentrate
with a lower salinity than typically associated with the term ‘brine’.
A desalination plant water recovery ratio (RR), deﬁned as the volu-
metric processing efﬁciency of the puriﬁcation process (Harvey, 2008), in-
dicates the proportion of intake water that is converted into high quality
(low salinity) water for sectoral use. The remaining water (calculated as
(1 −RR)) is the proportion of intake water being converted into a
waste (brine) stream, which requires management. For example, a desa-
lination plant operating with a recovery ratio of 0.4 means that 40% of in-
take water is converted into product water, and by extension 60% of
intake water is converted into brine. The RR of a desalination plant is de-
pendent on and controlled by a number of factors (Xu et al., 2013). Differ-
ent desalination technologies are associated with variations in RR, with
membrane technologies typically associated with a much higher RR
1344 E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
than possible with thermal technologies (Xu et al., 2013). The feedwater
quality is also important, with it being much more difﬁcult (and expen-
sive) to operate desalination plants at a high level of water recovery
when the feedwater salinity is high (Harvey, 2008).
With the aim of providing a global assessment of the research and
practice around desalination, the objectives of this study are to:
(1) share an insight into the historical development of desalination;
(2) provide a state-of-the-art outlook on the status of des alination, consid-
ering the number of desalination facilities and their associated treatment
capacity with regards to aspects such as geographical distribution, desali-
nation technologies, feedwater types and water uses; and (3) assess brine
production from desalination facilities and the management implications
of the produced brine. This study therefore seeks to update the literature
on the state of desalination in both research and practice, which is out-
dated. Furthermore, this study makes the ﬁrst comprehensive quantiﬁca-
tion of the volume of brine produced by desalination facilities, employing
a novel methodology that considers the efﬁciency of desalination plants
based on both their operating technology and the feedwater type.
2.1. Global status of desalination: research and practice
2.1.1. Desalination in research
A bibliometric analysis was conducted to evaluate the major re-
search trends in the ﬁeld of desalination.The Science Citation Index Ex-
panded (SCI-EXPANDED) from the Web of Science Core collection was
used for the time period 1980 to 2018. This study ﬁrstly categorises de-
salination publications based on major research theme (‘technology’,
‘environment’,‘economic and energy’and ‘social interests’). Subse-
quently, considering the ‘technology’category, trends in research on
speciﬁc technologies (‘Reverse Osmosis’,‘Multi-Effect Distillation’,
‘Multi-Stage Flash’,‘Electrodialysis’,‘Emerging’and ‘Other’) were exam-
ined. ‘Emerging’refers to technologies largely in the R&D phase (For-
ward Osmosis, Membrane Distillation and Nanoﬁltration) whereas
older, less prevalent technologies were categorised as ‘other’(Humidiﬁ-
cation-Dehumidiﬁcation, Solar Stills and Vapour Compression). The
precise methodology adopted for the bibliometric study is presented
in the Supplementary material.
2.1.2. Desalination in practice
A global database containing information on approximately 20,000
desalination plants (version of 2018) was obtained from Global Water
Intelligence (GWI) (https://www.desaldata.com). The database con-
tains information on the plant status, operational year, plant capacity,
geographic location(region, country,coordinates), customer type,desa-
lination technology and feedwater type of each individual desalination
plant. The precise geographic location of each desalination plant was
plotted in ArcGIS using latitude and longitude data. The rest of the
data was tabulated using pivot tables in Microsoft Excel to assess statis-
tics of multiple desalination plants per region, technology and other cat-
egories. Desalination data (number and capacity of plants) was
subsequently analysed at the global, regional and national scale. The
speciﬁcs within each category by which the global state of desalination
was analysed are as follows.
Plant status was categorised as either 1) Online; 2) Presumed online;
3) Construction; 4) Presumed ofﬂine; or 5) Ofﬂine. In this study, desali-
nation plants were considered ‘Operational’if they were classiﬁed as ei-
ther ‘Online’,‘Presumed online’or ‘Construction’. Operational year
refers to the year in which the desalination plant opened, assigned
unanimously as 2020 for all plants currently in construction. Plant desa-
lination capacity, or the volume of high quality product water produced
for human use, is provided in m
/day for each desalination plant.
Eight geographic regions were identiﬁed:1)EastAsia&Paciﬁc;
2) Eastern Europe & Central Asia; 3) Latin America & Caribbean; 4) Mid-
dle East & North Africa; 5) North America; 6) Southern Asia; 7) Sub-
Saharan Africa; and 8) Western Europe. Country data was used to assign
each desalination plant to one of four economic levels based on the 2018
World Bank Income groups, whereby GNI per capita ($) is estimated
using the World Bank Atlas method. Countries are assigned to one of
four economic classiﬁcations: 1) High income (N$12,056 GNI per
capita); 2) Upper middle income ($3896 to $12,055); 3) Lower middle
income ($966 to $3895); and 4) Low income (b$995).
The sector (or ‘customer type’) for each desalination plant was sep-
arated into six categories: 1) Municipal (including tourist drinking
water facilities); 2) Industry; 3) Power stations; 4) Irrigation; 5) Mili-
tary; and 6) Other. ‘Other’comprises uses of Demonstration, Process
and Water Injection, which are not considered separately as they ac-
count for b0.2% of total desalinated water use.
Feedwater type is separated into six categories in DesalData (2018)
expressed in ppm Total Dissolved Solids (TDS): 1) Seawater (SW)
[20,000–50,000 ppm TDS]; 2) Brackish water (BW) [3000–20,000 ppm
TDS]; 3) River water (RW) [500–3000 ppm TDS]; 4) Pure water (PW)
[b500 ppm TDS]; 5) Brine (BR) [N50,000 ppm TDS]; and 6) Wastewater
(WW). Despite having a typically high base quality (low salinity), desali-
nation of RW is practiced for a range of different sectoral uses (e.g. drink-
ing water, irrigation) to reduce water salinity below speciﬁc sectoral
thresholds. PW as a feedwater source is typically used for industrial appli-
cations which require very high quality (low salinity) water, such as the
pharmaceutical and food production industries.
Desalination technology was separated into seven categories: 1) Re-
verse Osmosis (RO); 2) Multi-Stage Flash (MSF); 3) Multi-Effect Distil-
lation (MED); 4) Nanoﬁltration (NF); 5) Electrodialysis/Electrodialysis
Reversal (ED); (6) Electrodeionization (EDI); and 7) Other. ‘Other’in-
cludeda varietyof technologiessuch as 1) Forward Osmosis (FO); 2) Hy-
brid (HYB); 3) Membrane distillation (MD); 4) Vapour compression
(VP); and 5) Unknown. As the technologies grouped together under
the ‘Other’category contribute a total of b1% of the total desalinated
water produced, these technologies were not considered individually.
2.2. Brine production
The volume of brine produced was determined at each individual
(operational) desalination plant using three factors contained in
DesalData (2018) - feedwater type, desalination technology and treat-
ment capacity (m
/day). We consider the water recovery ratios associ-
ated with different feedwater-desalination technology combinations
and calculate the brine production based on this recovery ratio and
the plant capacity using Eq. (1).
RR 1−RRðÞ ð1Þ
whereby Qb is the volume of brine produced (m
/day); Qd is the desa-
lination plant treatment capacity (m
/day) and; RR is the recovery ratio.
In total, 41 different feedwater type and desalination technology
combinations are currently operational. The recovery ratio associated
with each of these feedwater-technology combinations was determined
using two methods. Firstly, a literature study was conducted in order to
identify values of recovery ratios (or % water efﬁciency) for different
technologies and feedwater types reported in existing studies. When
recovery ratios were expressed as a range, the midpoint was used. In
total, 89 recovery ratios were found in the literature across a range of
feedwater-technology combinations. Secondly, inﬂuent and efﬂuent
salinity data from individual desalination plants operating with
membrane technologies was used to estimate recovery ratios using
Eqs. (2) and (3) (Bashitialshaaer et al., 2009).
1345E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
whereby Sb is the brine salinity and Sf is the feedwater salinity, with
both salinities expressed in the same units (e.g. mS/cm for EC, mg/l for
We obtained 30 additional recovery ratios using this method, which
were combined with recovery ratios identiﬁed in the literature to pro-
duce 119 records. From this, average recovery ratios could be identiﬁed
for 18 of the 41 technology-feedwater. Whilst this coverage might
seem low, desalination-technology combinations are not all equally
prevalent in terms of number of plants and desalination capacity.
These 14 combinations account for N80% of the total desalinated water
produced globally, with the top three combinations (seawater (SW)-
RO, brackish water (BW)-RO and SW-MSF) accounting for 70% of the
produced desalinated water alone. In order to determine recovery ratios
for the remaining feedwater-technology combinations, a number of as-
sumptions and estimations were made (Table 1).
Latitude and longitude data was used to calculate the distance of
each desalination plant from the nearest coastline using the Spatial An-
alyst tool in ArcGIS. Combined with the estimated brine production for
each desalination plant, we calculated the volume of brine produced
at different distances from the coastline to consider the implications
for brine management.
3.1. Research trends in desalination
Trends in the research history of desalination are displayed in Fig. 1.
Approximately 16,500 publications were found to have been produced
on the topic of desalination since 1980. Research in desalination has
grown exponentially, with the total number of publications approxi-
mately doubling with each ﬁve-year period (e.g. ~5000 in 2010 to
~11,000 in 2015). The large majority of publications focus on technolog-
ical aspects of desalination (e.g. 75% in 2005). As such, desalination lit-
erature focusing on technological aspects has driven the overall trend
in desalination research. Whilst the proportion of desalination literature
covering technological aspects is still high (72%), there has been an
emergence of literature covering alternative aspects of desalination,
particularly related to economics and energy and environmental con-
cerns. The number of publications considering economic aspects of de-
salination has increased dramatically in recent decades, from b400 in
2000 to N5000 in 2018. Historically, the environmental impacts of desa-
lination were severely neglected, with just 118 publications before
2000. However, literature published in this category is now increasing
at the fastest rate, with an additional ~2000 publications since 2000.
The number of publications addressing socio-political aspects of desali-
nation is relatively low. Desalination is not typically associated with so-
cial opposition and conﬂict associated with other water supply schemes
such as river regulation (e.g. dam buildings) and water transfers (March
et al., 2014), which may in part explain the lack of publications. Further-
more, desalination operations are not typically associated with the
gender issues and community-based factors associated with other un-
conventional water resources, such as fog water harvesting (Qadir
et al., 2018;Lucier and Qadir, 2018). However, desalinated operations
are associated with some important (and under-researched) policy-
related aspects, such as the lack of speciﬁc water standards for desali-
nated water for both the municipal (Chen et al., 2015) and agricultural
sectors (Martinez-Alvarez et al., 2016). As desalination continues to be-
come a more prevalent water resources management technology in the
future, the number of publications across all categories, and especially
environmental and socio-political themes, is expected to increase
Publications addressing technological aspects have dominated the
research history of desalination (Fig. 1). Fig. 2 further explores this
trend by categorising ‘technological’publications by speciﬁc technol-
ogy. RO is the most researched technology throughout the entire time
period, with the number of publications approximately doubling each
ﬁve-year period. Research into ‘emerging’technologies (FO, MD and
NF) is increasing at the most rapid pace with increasing recognisation
of their potential advantages over existing commercial technologies.
These include factors such as operating at higher water recovery ratios
and requiring less and/or sustainable energy (Subramani and Jacangelo,
2015). Thermal technologies (MED and MSF), despite accounting for a
signiﬁcant share in the amount of desalinated water produced, have re-
ceived comparativelylittle attention in recentliterature. Whilst publica-
tions addressing MSF and MED accounted for a signiﬁcant proportion of
research in the 1980s and 1990s, they are now the overall least
researched technologies. Concerns over the energy costs, efﬁciency
and environmental impacts of thermal processes, and the development
of more efﬁcient membrane technologies and techniques (particularly
RO), likely explain this trend.
3.2. Global state of desalination
There are 15,906 operational desalination plants with a total
desalination capacity of approximately 95.37 million m
(34.81 billion m
/year), constituting 81% and 93% of the total num-
ber and capacity of desalination plants ever built respectively
(Fig. 3a). Early desalination plants predominantly utilised thermal
technologies, located in oil-rich but water scarce regions, espe-
cially in the Middle East. For example, prior to the 1980s, 84% of
all global desalinated water was being produced by the two major
thermal technologies (MSF, MED). The rise in the use of membrane
technologies post-1980, in particular RO, gradually shifted the dominance
away from thermal technologies. In 2000, the volumes of desalinated
water produced by thermal technologies (dominated by MSF) and RO
were approximately equal at 11.6 million m
/day and 11.4 m
spectively, together accounting for 93% of the total volume of desalinated
water produced (Fig. 3b). Since 2000, both the number and capacity of RO
plants has risen exponentially, whilst thermal technologies have only ex-
perienced marginal increases (Fig. 3b). The current production of desali-
nated water from reverse osmosis now stands at 65.5 million m
accounting for 69% of the volume of desalinated water produced.
The spatial distribution, size and customer type of desalination facil-
ities (N1000 m
/day) are displayed in Fig. 4. Large numbers of desalina-
tion facilities are located in the United States, China and Australia and
across the regions of Europe, North Africa and the Middle East. Rela-
tively few desalination facilities are located in South America and
Africa, with existing facilities predominantly designed to produce desa-
linated water for the industrial sector. Desalination plants globally are
concentrated on and around the coastline, with coastal desalination
plants also tending to be larger than inland desalination plants. Plants
producing municipal water are located worldwide, but are particularly
dominant in the Middle East & North Africa region. Comparatively,
Assumptions and estimations used determining the recovery ratios of feedwater-technol-
ogy combinations used in operational desalination plants.
1 When brackish water (BW) recovery is known, the water recovery ratio of
brine (BR) (TDS N50,000 ppm), seawater (SW) (TDS 20,000–50,000 ppm),
river water (RW) (TDS 500–3000 ppm) and pure water (PW) (TDS b500 ppm)
is assumed to be the 95th, 90th, 10th and 5th percentiles of brackish water
2 When brackish water (BW) recovery is unknown but seawater water (SW)
recovery is known, the water recovery ratio of brine water (BR), brackish
water (BW), river water (RW) and pure water (PW) is assumed to be the 90th,
25th, 10th and 5th percentiles of seawater technologies respectively.
3 The recovery rate of wastewater (WW) for each technology is assumed to be
equal to the recovery rate of brackish water for the same technology.
1 Other technologies cover a range of different technologies. An estimated 40% water
recovery ratio was assigned for highly saline water (above 20,000 ppm) and 60%
recovery for brackish and slightly saline water sources (below 20,000 ppm).
1346 E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
Fig. 1. Number of desalination publications by categorisation (total, technical, social,environment, energy & economic).
Fig. 2. Number of publications by type of desalination technology (Reverse Osmosis [RO], Multi-Effect Distillation [MED], Multi-Stage Flash [MSF], Electrodialysis [ED]), emerging
technologies (N anoﬁltration [NF], Forward Osmos is [FO] and Membrane Distillation [MD]) and other (Humidiﬁcation-Dehumidiﬁcation [HDH], Solar Stills [SS] and Vapour
1347E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
there is a far greater proportion of desalination plants producing water
for non-municipal purposes in North America, Western Europe and East
Asia and Paciﬁc regions, whereby generation of water for industrial and
power applications also command large market shares (Fig. 4).
The number and capacity of desalination plants by geographic re-
gion, country income level and sectoral use of desalinated water
(Table 2) reveal that almost half of the global desalination capacity is lo-
cated in the Middle East and North Africa region (48%), with Saudi
Arabia (15.5%), the United Arab Emirates (10.1%) and Kuwait (3.7%)
being both the major producers in the region and globally. East Asia
and Paciﬁc and North America regions produce 18.4% and 11.9% of the
global desalinated water, primarily due to large capacities in China
(7.5%) and the USA (11.2%). The widespread use of desalination in
Spain (5.7%) accounts for over half of the total desalination in Western
Europe (9.2%). The global share in desalination capacity is lower for
Southern Asia (3.1%), Eastern Europe and Central Asia (2.4%) and Sub-
Saharan Africa (1.9%), where desalination is primarily restricted to
small facilities for private and industrial applications. The majority of
desalination facilities are located in high income countries (67%),
accounting for the majority of the global desalination capacity (71%).
Conversely, very few desalination plants are located in low income
countries, which contribute a negligible proportion (b0.1%) of the global
Whilst almost half of the total number of desalination plants pro-
duce water for the industrial sector, the municipal sector is the largest
user of desalinated water in terms of capacity. 62.3% of desalinated
water is produced for human consumption (municipal sector), com-
pared to 30.2% for industrial applications. This pattern occurs due to
the (typically) smaller capacity of industrial desalination facilities,
which average 3712 m
/day, compared to desalination plants producing
municipal water that average 12,126 m
/day. Whilst the municipal and
industrial sectors account for the vast majority of the global desalination
capacity, the power (4.8%) and irrigation (1.8%)sectors consume a small
but signiﬁcant proportion of produced desalinated water.
Of the desalination technologies, RO is by far the most dominant pro-
cess, accounting for 84% of the total number of operational desalination
plants, producing 69% (65.5 million m
/day) of the total global desali-
nated water (Fig. 5a). The two major thermal technologies, MSF and
Fig. 3. Trends in global desalination by (a) number and capacity of total and operational desalination facilities and (b) operational capacity by desalination technology.
Fig. 4. Global distribution of operational desalination facilities and capacities (N1000 m
/day) by sector user of produced water.
1348 E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
MED, despite being relatively few in number, produce the majority of
the remaining desalinated water, with market shares of 18% and 7% re-
spectively (Fig. 5a). In total, these three technologies account for 94% of
the total desalinated water produced, with plants using NF (3%), ED
(2%) and EDI (b1%) technologies producing smaller volume of desali-
nated water (Fig. 5a).
In terms of feedwater source, which is indicative of feedwater qual-
ity, SW desalination accounts for 61% of produced water (Fig. 5b). Desa-
lination of BW and RW produce the nextlargest volumes of desalinated
water, with market shares of 21% and 8% respectively (Fig. 5b). In total,
these three sources account for 90% of the total volume of desalinated
water produced, with the remainder being produced from WW (6%),
PW (4%) and BR (b1%).
Whilst Fig. 5 clearly demonstratesthe relative dominance of RO, MSF
and MED in terms of desalination technology, and SW, BW and RW in
terms of feedwater source, the combination of both these factors is im-
portant. Desalination technologies can be considered semi-specialised
in that they operate most efﬁciently when using particular source
water types, or that their economic viability is dependent on source
water type, and hence some feedwater-technology combinations are
signiﬁcantly more prevalent than others.
RO is a process that is economically viable across a range of
feedwater types, and hence the feedwater type used is dependent on
local availability (Fig. 5). 50% and 27% of the desalinated water that is
produced from RO desalination plants, accounting for 34% and 19% of
the global desalination capacity, originates from SW and BW water, re-
spectively. RO of RW (7%) and WW (5%) also contributes a signiﬁcant
proportion of the global desalination capacity. Comparatively, thermal
technologies are used almost exclusively for low quality (highly saline)
feedwater types. 96% of MSF plants and 80% of MED plants use
feedwater with N20,000 ppm TDS, the vast majority of which use sea
water. SW accounts for 99.9% and 92% of the total volume of desalinated
water produced by MSF andMED respectively, representing global mar-
ket shares of 18% and 6%. Conversely, plants operating with ED as the
desalination technology typically require water of a higher base quality
(lower salinity). 60% and 20% of the desalinated water produced by ED
originates as BW and RW respectively, contributing a small but signiﬁ-
cant proportion of the total global volume of desalinated water. In
total, eight feedwater-technology combinations (SW-RO, BW-RO, SW–
MSF, SW–MED, RW-RO, WW-RO, BW-ED, RW-ED) are responsible for
the production of over 90% of the global desalinated water.
Fig. 6 reveals the spatial distribution and size of large
/day) desalination plants operating under different
feedwater-technology combinations. Thermal desalination technologies
(MED, MSF) operating with sea water as the feedwater type are dominant
in the Middle East, with the exception of a large number of BW-RO plants
located in inland Saudi Arabia. Outside of this region, very few large ther-
mal plants exist, with RO being the dominant technology across a range of
feedwater types. For example, large desalination plants in Australia oper-
ate almost exclusively using RO technology, but with a variety of
feedwater types including SW, BW and WW. RO is also the dominant
technology across the United States, although the vast majority of desali-
nation plants operate using BW and RW, with only a small number of sea-
water plants located in California and Florida. Western Europe, and in
particular Spain, is dominated by RO using a variety of feedwater sources,
although there is also a signiﬁcant number of desalination plants operat-
ing using alternative technologies such as ED and NF. Lastly, SW-RO dom-
inates desalination in the coastal areas of Asia, although a signiﬁcant
number of BW- and RW-RO plants are located inland.
3.3. Brine production
The water recovery efﬁciency of desalination operations depends on
both the type of desalination technology and the quality of feedwater
used, and therefore both of these factors must be considered when
quantifying brine production (Xu et al., 2013). Table 3 displays the
water recovery ratios associated with the major feedwater-technology
combinations in operation.
For all technologies, the recovery ratio increases as the feedwater
quality increases (salinity decreases), with BR associated with the low-
est water recovery ratios and PW associated with the highest recovery
ratios. Feedwater type is a substantial determinant of the recovery
ratio associated with a particular technology. For example, SW-RO
operates at a substantially lower recovery ratio (0.42) compared to
BW-RO (0.65) and RW-RO (0.85). Similarly, BW-NF (0.83) is substan-
tially more efﬁcient than SW-NF (0.69). Individual desalination technol-
ogies are also associated with vastly different recovery ratios. Thermal
technologies (e.g. MSF, MED) are typically associated with much
lower recovery ratios than membrane technologies (e.g. RO, NF).For ex-
ample, the recovery ratio of MSF across all feedwater types is approxi-
mately half that of RO. The water recovery ratio of other membrane
technologies (NF, ED, EDI, EDR) is substantially higher than RO across
all feedwater types.
Energy requirements, and hence economic costs, vary dependingon
feedwater type. For membrane technologies, low salinity feedwater
types (e.g. RW) require less applied pressure than high salinity
feedwater types (e.g. SW) for desalination, causing lower energy con-
sumption per unit water produced (Ghaffour et al., 2013). This results
in substantially lower investment costs (Ghaffour et al., 2013). How-
ever, highly efﬁcient membrane technologies are rarely used for desali-
nation of highly saline feedwater types, with a total of just 0.01%
desalinated water being produced by SW or BR in combination with
NF, ED, EDI and EDR. For highly saline feedwater types, RO and thermal
processes (e.g. MSF, MED) dominate. Whilst thermal technologies (par-
ticularly MED) are associated with higher energy consumption, the eco-
nomic cost of desalting SW is comparable to RO due to lower
investment costs (Ghaffour et al., 2013).
Current global brine production stands at 141.5 million m
taling 51.7 billion m
/year (Table 4). This value is approximately 50%
greater than the total volume of desalinated water produced globally.
Global brine production is concentrated in the Middle East and North
Africa, which produces almost 100 million m
/day of brine, accounting
for 70.3% of global brine production. This value is approximately double
the volume of desalinated water produced, indicating that desalination
plants in this region operate at an (very low) average water recovery
Number,capacity and globalshare of operationaldesalinationplants by region,country in-
come level and sector use.
Number of desalination
Global 15,906 95.37 100
Middle East and North Africa 4826 45.32 47.5
East Asia and Paciﬁc 3505 17.52 18.4
North America 2341 11.34 11.9
Western Europe 2337 8.75 9.2
Latin America and Caribbean 1373 5.46 5.7
Southern Asia 655 2.94 3.1
Eastern Europe and Central Asia 566 2.26 2.4
Sub-Saharan Africa 303 1.78 1.9
High 10,684 67.24 70.5
Upper middle 3075 19.16 20.1
Lower middle 2056 8.88 9.3
Low 53 0.04 0.0
Municipal 6055 59.39 62.3
Industry 7757 28.80 30.2
Power 1096 4.56 4.8
Irrigation 395 1.69 1.8
Military 412 0.59 0.6
Other 191 0.90 0.4
1349E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
ratio of 0.25. Comparatively, all other regions produce substantially
lower volumes of brine, with East Asia and Paciﬁc (10.5%), Western
Europe (5.9%) and North America (3.9%) having the next largest shares.
Interestingly, these regions produce a substantially lower volume of
brine than the amount of desalinated water they produce, indicating
that recovery ratios are generally high. This is particularly apparent for
North America, which produces a substantially lower volume of brine
than it does desalinated water, suggesting that desalination facilities op-
erate at an average recovery ratio of 0.75. In other geographical regions,
brine production is approximately equivalent to desalinated water pro-
duction (i.e. RR = 0.5).
As with desalinated water production, high income countries pro-
duce the vast majority of global brine (77.9%). It should be noted that
‘high income’includes both countries from both highly developed
world regions (e.g. North America, Western Europe), whose brine pro-
duction tends to be smallerrelative to the desalinated water production,
and the oil-rich Gulf nations who typically employ thermal desalination
technologies with low recovery ratios, hence high brine production. For
example, Saudi Arabia alone produces 31.53 million m
accounting for 22.2% of the global share. The next three largest pro-
ducers of brine are also oil-rich countries, with the UAE, Kuwait and
Qatar having 20.2%, 6.6% and 5.8% shares in global brine production re-
spectively. Together, these four nations produce 32% of global desali-
nated water and 55% of the total brine. Comparatively, the USA
produces 10.91 million m
/day of desalinated water (11.4% global
share) but produces just 5.28 million m
/day of brine (3.7% global
share). Upper middle income, lower middle income and low income
countries tend to produce quantities of brine similar to that of their re-
spective desalination capacities.
Water produced for the municipal sector is by far the largest pro-
ducer of both desalinated water and brine, although the quantity of
brine produced is much greater. This pattern arises primarily due to
the vast quantity of desalinated drinking water produced for the Gulf
nations, whereby thermal technologies operating with SW dominate.
Both the industrial and agricultural sectors produce lower quantities
of brine than desalinated water, indicating desalinated water for these
sectors is produced by feedwater-technology combinations with higher
water recovery ratios. This is particularly pronounced in the agricultural
Fig. 5. Number and capacity of operational desalination facilities by (a) technology and (b) feedwater type.
1350 E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
sector due to the dominance of high-quality (low salinity) feedwater
sources used for producing desalinated water for use in agriculture
The geographical location of brine production inﬂuences the eco-
nomic and technical viability of different methods of brine disposal
(Arnal et al., 2005). Desalination plants located near the shoreline
often discharge untreated brine directly into saline surface water bodies
(e.g. oceans, seas) (Arnal et al., 2005). As almost half of brine is pro-
duced within 1 km of the coastline, rising to almost 80% produced
within 10 km, ocean disposal is assumed to be the dominant brine dis-
posal method worldwide (Table 5). The countries producing large vol-
umes of brine (N1 million m
/day) in coastal locations are largely
concentrated in the Middle East and North Africa (e.g. UAE, Saudi
Arabia) and South-East Asia (China, India), and in the USA and
Australia (Fig. 7a). The volume ofbrine produced in many of these coun-
tries far exceeds 1 million m
/day, particularly in the Middle East. In this
region, the four largest brine producers (UAE, Saudi Arabia, Qatar,
Kuwait) account for 72.2 million m
/day of the brine that is produced
within 10 km of the coastline.
Whilst brine disposal into saline surface water bodies raises some
important environmental concerns, this option is extremely economical
(Arnal et al., 2005). However, this option is often not available for inland
desalination plants, which account for a smaller yet signiﬁcant propor-
tion of the volume of brine being produced. Almost 22 million m
of brine is produced at a distance of N50 km from the nearest coastline
(Table 5). Despite the large volume of brine produced inland, very few
economically viable and environmentally sound brine management op-
tions exist (Arnal et al., 2005). Brine produced inland poses an impor-
tant problem for many countries located in all world regions, with 64
countries producing N10,000 m
/day of brine in inland locations
(Fig. 7b). Whereas the volume of brine produced in coastal locations is
largely concentrated in the Middle East, inland brine production is a
particular issue in other locations such as China (3.82 million m
USA (2.42 million m
/day) and Spain (1.01 million m
/day) (Fig. 7b).
Whilst Fig. 5 considered the production of desalinated water by
technology and feedwater type separately, Fig. 8a combines these two
elements, displaying the 6 major feedwater-technology combinations
by volume of desalinated water produced. As displayed in Fig. 5,ROis
Fig. 6. Global distribution of large desalination plants by capacity, feedwater type and desalination technology.
Recovery ratio of different feedwater-technology combinations producing desalinated
Feedwater type Technology
RO MSF MED NF ED EDI EDR Other
Seawater (SW) 0.42 0.22 0.25 0.69 0.86 0.90 0.40
Brackish (BW) 0.65 0.33 0.34 0.83 0.90 0.97 0.90 0.60
River (RW) 0.81 0.35 0.86 0.90 0.97 0.96 0.60
0.86 0.35 0.89 0.90 0.97 0.96 0.60
Brine (BR) 0.19 0.09 0.12 0.85 0.40
0.65 0.33 0.34 0.83 0.90 0.97 0.60
Based on data from: Ahmed et al. (2001),Allison (1993),Almu lla et al. (2003),
Bashitialshaaer et al. (2007),Belatoui et al. (2017),Bleninger et al. (2010),Costa and De
Pinho (2006),DesalData (2018),Efraty and Gal (2012),Fernández-Torquemada et al.
(2005),Garcia et al. (2011),Gomez and Cath (2011),Greenlee et al. (2009),Hajbi et al.
(2010),Harvey ( 2008),Kelkar et al. (2003),Khawaji et al . (2007),Korngold et al.
(2009),Kurihara et al . (2001),Macedonio and Drioli (2008),Mohamed et al. (2005),
Mohsen and Gammoh (2010),Pilat (2001),Pearce et al. (2004),Qiu and Davies (2012),
Qurie et al. (2013),Singh (2009),Stover (2013),Valero and Arbós (2010),Von Gottberg
et al. (2005),Voutchkov (2011),Wilf and Klinko (20 01),Xu et al. (2013),Younos
(2005) and Zhou et al. (2015).
PW refers to water of a high base quality (low salinity), but that is desalinated pri-
marily for industrial applications requiring very low salinity water (e.g. food processing,
WW refers to reject water from municipal and industrial sources undergoing desali-
nation in speciﬁc WW desalination facilities.
Brine production and share of global total by region, income level and sector use.
Global 141.5 100
Middle East & North Africa 99.4 70.3
East Asia & Paciﬁc 14.9 10.5
North America 5.6 3.9
Western Europe 8.4 5.9
Latin America & Caribbean 5.6 3.9
Southern Asia 3.7 2.6
Eastern Europe & Central Asia 2.5 1.8
Sub-Saharan Africa 1.5 1.0
High 110.2 77.9
Upper middle 20.7 14.6
Lower middle 10.5 7.4
Low 0.03 0.0
Municipal 106.5 75.2
Industry 27.4 19.3
Power stations 5.8 4.1
Irrigation 1.1 0.8
Military 0.5 0.3
Other 0.3 0.2
1351E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
the dominant desalination technology, with signiﬁcant additional con-
tributions from MSF and MED technologies (Fig. 8a). However, large
volumes of desalination water are produced by RO from a variety of
feedwater sources (SW, BW, RW and WW), whilst the two thermal
technologies almost exclusively use SW. The share in brine production
from each desalination feedwater-technology combination is displayed
in Fig. 8b. The vast majority of brine, 124.5 million m
comes from SW desalination plants. Comparatively, brine production
from desalination plants operating with other feedwater types is
much smaller, with BW, RW and WW plants producing 10.23 (7.2%),
1.80 (1.3%) and 3.57 (2.5%) million m
/day, respectively. Individually,
SW-MSF accounts for the largest volume of brine production (43%),
with SW-RO (31%), SW-MED (12%) and BW-RO (7%) accounting for
the vast majority in the remainder of the global share (Fig. 8b).
Clear discrepancies exist when comparing the volume of desalinated
water produced to the volume of brine water produced by different
feedwater-technology combinations (Fig. 8c). These differences are di-
rectly related to the different water recovery ratios associated with de-
salination plants operating with different feedwater-technology
combinations. The greater the volumetric processing efﬁciency of the
desalination process, the smaller the proportion of brine produced rela-
tive to the volume of desalinated water produced. For example, RW-RO
operates at very high water recovery ratios, therefore producing
6.8 million m
/day of desalinated water (7.1% global share) whilst pro-
ducing just 1.6 million m
/day of brine (1.1% global share). Conversely,
whilst SW-MSF desalination plants produce 16.7 million m
(17.6% global share) of desalinated water, brine production totals
60.1 million m
/day (43% global share).
Owing to recent, rapid developments in desalination research, the
last comprehensive assessment (Tanaka and Ho, 2011) available in the
academic literature is outdated. This study presents statistical analysis
of the scientiﬁc literature covering an array of desalination topics since
1980, addressing a diverse range of social and technical aspects with
respect to publication date, revealing patterns in publishing trends.
Our ﬁndings suggest that research in desalination has increased expo-
nentially over the last 40 years, coinciding with the more widespread
recognition of the value of these technologies for water resources man-
agement. Research has particularly considered the technological aspects
of desalination, withthe vast number of publications addressing ROand
novel (‘emerging’) techniques that can produce desalinated water at
lower economic costs and with less negative environmental implica-
tions (Arnal et al., 2005). Developments in novel desalination tech-
niques, membrane materials and modules dominate the technological
literature (Greenlee et al., 2009). Publications addressing economic, en-
vironmental and socio-political aspects of desalination are rapidly
increasing with expansions in desalination. In particular, the environ-
mental impacts associated with hypersaline brinedischarges from desa-
lination plants have received increased attention in recent research,
coinciding with water scarcity intensiﬁcation and the resultant expan-
sion in desalination operations in the USA, Europe and Australia
(Roberts et al., 2010).
Brine production and share of global total by distance to coastline.
Distance to coastline Brine production
b1 km 69.0 48.8
1km–10 km 43.2 30.5
10 km–50 km 7.3 5.2
N50 km 22.0 15.5
Fig. 7. Volume of brine produced per country at a distance of a) b10 km and b) N50 km from the coastline.
1352 E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
With regards to desalination in practice, the current state-of-the-art
in the global desalination situation in existing academic literature is ei-
ther a) severely outdated or b) derived from incomplete sources. This
study usesthe largest and the most complete desalination dataset avail-
able (DesalData, 2018) to comprehensively analyse the global state of
desalination with respect to desalination geographical distribution,sec-
tor use, technology and feedwater type. Our ﬁndings demonstrate that
the global desalination capacity far exceeds values frequently cited in
the literature, due to both the vast expansion in desalination operations
that have taken place across the globe in the last decade and the cover-
age of the dataset used. The major uncertainty related to these results is
due to the completeness of the desalination database, which was
minimised by using a very high-quality dataset (DesalData, 2018).
Accurate quantiﬁcations of the volume of desalinated water pro-
duced for human use at different spatial scales is associated with a
range of management implications. For example, in order to more rep-
resentatively assess the degree of water scarcity, unconventional water
resources and management practices must be included (Vanham et al.,
2018;Jones and van Vliet, 2018). The exclusion of desalination from
quantiﬁcations of water scarcity is identiﬁed as a major shortcoming
of SDG 6.4.2 (Vanham et al., 2018), and hence accurate data on the vol-
ume of desalinated waterproduced is importantfor assessing the actual
status of water availability. This is particularly important as water scar-
city has been identiﬁed as a key challenge, which is expected to inten-
sify in the future (Richter et al., 2013).
The importance of desalination for alleviating water scarcity
and safeguarding water resources for human use should not be
underestimated. Based on FAO AQUASTAT water withdrawal data
and desalination capacity data from DesalData (2018),eightcoun-
tries produce more desalination water than they withdraw for
human use (The Maldives, Singapore, Qatar, Malta, Antigua and
Barbuda, Kuwait, The Bahamas and Bahrain). A further six coun-
tries meet over 50% of their water withdrawals through desalina-
tion (Equatorial Guinea, UAE, Seychelles, Cape Verde, Oman and
Barbados). As demonstrated through these countries, desalination
is an essential technology in the Middle East and for small island
nations which typically lack renewable water resources.
Whilst there are demonstrated beneﬁts from desalinated water,
there are concerns related to the volume and salinity of brine produced
as a waste of desalination process. It poses some of the biggest con-
straints to more widespread development of desalination operations,
in addition to representing a signiﬁcant proportion of the economic
costs of the process (5–33%) (Ahmed et al., 2001). Therefore, quantify-
ing the volume of brine produced by desalination plants operating
with different feedwater types and technologies is essential for consid-
ering the potential environmental and economic costs associated with
The volume of brine being produced from desalination plants glob-
ally is largely unknown, with the only estimates available in the litera-
ture assuming that the volume of brine is equivalent to the volume of
desalinated water produced (Liu et al., 2016;Akinaga et al., 2018), re-
gardless of the feedwater type or desalination technology. Our study
considers the inﬂuence of both feedwater type and desalination tech-
nology on the water recovery ratio, deriving values for the vast majority
of feedwater-technology combinations producing desalinated water.
This information is applied with respect to the treatment capacity of in-
dividual desalination plant to determine the volume of brine produc-
tion, thus representing a ﬁrst comprehensive attempt to accurately
quantify brine production.
Our ﬁndings also indicate that the volume of brine produced far ex-
ceeds the volume of desalinated water produced (by ~50%), and hence
that the current quantiﬁcations of volume of brine produced are gross
underestimations. However, the uncertainties associated with our
method should be considered. In our brine assessment methodology,
we assigned recovery ratios based solely on thefeedwater type and de-
salination technology producing desalinated water at each plant, with
no consideration of local conditions in these plants. Evidence suggests
that site-speciﬁc local conditions may also inﬂuence a desalination
plants recovery ratio (Xu et al., 2013). For example, the effect of varia-
tions in feedwater salinity within each ‘feedwater type’categorisation
(e.g. seawater) on the recovery ratio is overlooked as a result of using
Fig. 8. Major desalination feedwater-technology combinations by (a ) global share in the desalinated water production (%), (b) global sha re in brine production (%) and (c) total
desalination capacity and volume of brine produced (million m
1353E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
the average. Other factors that may inﬂuence the speciﬁc recovery of
each individual desalination plant include speciﬁcplantdesign(e.g.
type of membrane used in desalination process), product water quality
requirements (e.g. salinity), energy source and brine disposal method-
ology. Furthermore, whilst desalination plant recovery ratios are avail-
able in the literature, the number of values used for determining
recovery ratios for some feedwater-technology combinations was low.
For some feedwater-technology combinations, no values were found
in the literature, and therefore a number of assumptions and estima-
tions had to be made (Table 1). This uncertainty was minimised as re-
covery ratios were found in the literature for all major feedwater-
technology combinations, capturing the vast majority of the total desa-
lination capacity (N80%).
With increasing water demandscoupled with water scarcity intensi-
ﬁcation,desalination is expected to expand rapidly in the future. The ex-
pected expansion in desalination capacity will be commensurate with
an increase in the volume of brine produced. Management of the reject
brine is the still a major problem of desalination (Roberts et al., 2010;
Elimelech and Phillip, 2011;Mezher et al., 2011;Wenten, 2016), con-
taining both elevated salinity (relativeto feedwater type)and chemicals
used during pre- and post-treatment phases in the desalination opera-
tion (Wenten et al., 2016). Traditionally, a variety of brine disposal
methods have been used, including direct discharge into oceans, surface
water or sewers, deep well injection and brine evaporation ponds
(Morillo et al., 2014). The geographical location at which brine is pro-
duced inﬂuences the brine disposal method –desalination plants lo-
cated near to large surface saline water bodies (ocean, seas) often
discharge untreated waste brine directly into these water bodies
(Arnal et al., 2005). Conversely, desalination plants located inland may
not have a surface water discharge option available, and hence alterna-
tive brine disposal methods are required, of which there are few eco-
nomically viable options (Arnal et al., 2005;Brady et al., 2005;Morillo
et al., 2014).
Whilst the majority of brine is produced near to the coastline
(Fig. 7a), with almost 80% of brine produced within 10 km (Table 5), a
substantial volume of brine is produced in geographic locations where
surface water discharge is likely not possible (Fig. 7b, Table 5). In addi-
tion, there are a variety of environmental concerns associated with the
discharge of hypersaline brine into surface water bodies (Einav et al.,
2002;Roberts et al., 2010;Palomar and Losada, 2011). Major concerns
are related to the ecological effects associated with physio-chemical al-
terations (e.g. increased salinity) to seawater around brine discharge
outlets and the discharge of toxic chemicals used in water pre-
treatment or as anti-scalants and anti-foulants in the desalination pro-
cess (Einav et al., 2002;Roberts et al., 2010;Ketsetzi et al., 2008).
When continually discharged to surface waters, these factors pose
risks to ocean life and marine ecosystems (Gacia et al., 2007;Palomar
and Losada, 2011;Meneses et al., 2010). The high salinity of brine causes
elevated density in comparison to the salinity of the receiving waters,
which can form “brine underﬂows”that deplete dissolved oxygen
(DO) in the receiving waters. High salinity and reduced DO levels can
have profound impacts on benthic organisms, which can translate into
ecological effects observable throughout the food chain (Rabinowitz,
2016;Frank et al., 2017). A combination of these factors necessitates
the development of new brine management strategies that are both
economically feasible and environmentally sound.
Recent efforts have focused on ways to treat or use brine in order to
minimise or eliminate the negative environmental impacts associated
with brine disposal (Morillo et al., 2014;Wenten et al., 2017) and/or
to partially or fully offset the economic costs associated with brine dis-
posal (Kesieme et al., 2013;Morillo et al., 2014). These efforts cover a
range of techniques with variable levels of complexity and cost. For ex-
ample, mixing brine with alternative water sources of a lower salinity
(e.g. treated wastewater, power-plant cooling water) can reduce brine
salinity by dilution (Giwa et al., 2017). Pressurised dispersion nozzles
can promote mixing of brine waters with receiving waters, restricting
bottom ponding (Roberts, 2015). Techniques such as bipolar membrane
electrodialysis (BMED) can convert brine into acid and base products for
reuse, such as NaOH and HCl (Ibáñez et al., 2013;Morillo et al., 2014).
Metal recovery from brine offers a valuable source of many scarce
metals (e.g. uranium), whilst potentially reducing environmental im-
pacts associated with mining (Morillo et al., 2014;Loganathan et al.,
2017). The high economic costs and energy demands of brine treatment
and mineral recovery methods remain a signiﬁcant barrier to more
widespread application (Kaplan et al., 2017). Comprehensive reviews
of the recent techniques, technologies and innovations in brinemanage-
ment are provided by Morillo et al. (2014) and Giwa et al. (2017).
Other potential economic opportunities associated with brine pro-
duction have also sparked a wave in innovation in brine management
that seeksto turn an environmental problem into an economic opportu-
nity (Sánchez et al., 2015). For example, Blackwell et al. (2005) identi-
ﬁed sequential biological concentration (SBC) of saline drainage
streams creating a number of ﬁnancial opportunities, whilst concentrat-
ing the waste stream into a manageable volume. Qadir et al. (2015) sug-
gested that integrating agriculture and aquaculture systems based on
the SBC system using saline drainage water sequentially has the poten-
tial for commercial, social and environmental gains. Reject brine has
been used for aquaculture, with increases in ﬁsh biomass of 300%
achieved (ICBA, 2018). Reject brine has also been successfully used for
Spirulina cultivation and the irrigation of halophytic forage shrubs and
crops although this method was unable to prevent progressive land
salinisation (Sánchez et al., 2015).
Aside from treating or using reject brine, a method to reduce the
volume of brine produced is to improve the water recovery ratio of de-
salination plants. Desalination plants operating with a high RR are
favourable in that they both maximise the use of (often scarce) water
resources as in the case of river and brackish water desalination plants
and create a lower volume of concentrate for disposal (Harvey, 2008),
reducing theeconomic costs associated with brine disposal. High recov-
ery rates can also reduce the cost of pre-treatment prior to desalination
and post-treatment of brine (Lachish, 2002). However, attaining higher
RRs generally increases energy demands and hence treatment costs
(Lachish, 2002), increasing greenhouse gas emissions if the desalination
plant is powered by fossil fuels (Martin-Gorriz et al., 2014;Darre and
Toor, 2018). Whilst the reduced volume of brine associated with higher
RRs might have positive environmental implications, the brine salt con-
centration will be increased (Ahmed et al., 2001) which could poten-
tially pose harmful risks to the aquatic environment following disposal
(Bashitialshaaer et al., 2009). Determining the optimal recovery ratio
for desalination plants is therefore an economic, environmental and
technical challenge, requiring consideration on a site-by-site basis.
5. Conclusions & outlook
Against the backdrop of increasing global water scarcity, desalinated
water is increasingly becoming a viable option to narrow the water
demand-supply gap, particularly in addressing domestic and municipal
needs. Desalinated water can substantially extend the volume of high-
quality water supplies available for human use. A steady and assured
supply of high-quality water is crucially important in an era when the
world at large is embarking on the Sustainable Development Agenda
to ensure access to safe water for all by 2030, and for the achievement
of SDG 6 to safeguard water supplies for current and future generations.
In addition to SDG 6, a variety of other SDGs are inextricably linked with
water resources management, such as SDG 2 aiming at zero hunger,
SDG 3 ensuring healthy lives, SDG 8 promoting sustainable economic
growth, SDG 11 making cities and human settlements inclusive, and
SDG 13 combating climate change. These SDGs have water-related tar-
gets that must be achieved before their ultimate realisation is possible.
Although desalination can provide an unlimited, climate-independent
and steady supply of high-quality water, there are speciﬁc challenges to
harness the vast potential of desalinated water, such as relatively high
1354 E. Jones et al. / Science of the Total Environment 657 (2019) 1343–1356
economic costs and a variety of environmental concerns. A major envi-
ronmental concern arises from the large volume of brine produced in
the desalination process that requires management. Brine management
is both economically expensive and technically difﬁcult, and hence most
desalination plants discharge untreated brine directly into the environ-
ment. Addressing these challenges, research studies have demonstrated
that there are economic opportunities associated with brine, such as com-
mercial salt and metal recovery and use of brine in ﬁsh and halophyte
production systems. There is a need to translate such research to convert
an environmental problem into an economic opportunity. This is particu-
larly important in countries producing large volumes of brine with rela-
tively low efﬁciencies, such as Saudi Arabia, UAE, Kuwait and Qatar.
Although smaller amounts of desalinated water are used for the
power and irrigation sectors, water is desalinated primarily for mu-
nicipal and industrial purposes. In this regard, desalinated water
provides a safe and sustainable source of good-quality water for do-
mestic purposes. Such potable water supplies are critically impor-
tant in water scarce areas where water quality deterioration is also
on the increase. The use of desalinated water in producing high-
value crops and crop commodities would be another avenue whilst
considering expansion of desalinated water to other sectors (Silber
et al., 2015).
Due primarily to the relatively high economic costs, desalination is
currently concentrated in high income and developed countries. There
is a need to make desalination technologies more affordable and extend
them to low income and lower middle income countries, increasing the
viability of desalination for addressing SDG 6 in areas that develop-
ments have previously been limited by high economic costs. To do
this, technological reﬁnement for low environmental impacts and eco-
nomic costs, along with innovative ﬁnancial mechanisms to support
the sustainability of desalination schemes, will likely be required. The
expansion pattern and economics of desalination facilities in recent de-
cades suggest a positive and promising outlook for expansion in desali-
nation facilities around the world.
This work is part of the UNU-INWEH's project on Unconventional
Water Resources. UNU-INWEH is supported by the Government of
Canada through Global Affairs Canada. Michelle van Vliet was ﬁnan-
cially supported by a Veni-grant (project no. 863.14.008) of NWO Earth
and Life Sciences (ALW).
The authors declare no conﬂict of interest.
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