DESALINATiON

ELSEVIER Desalination 152 (2002) 141-154

www.elsevier.com/locate/desal

The footprint of the desalination processes on the environment

Rachel Einav”*, Kobi Hamssib, Dan Periyb

“Blue Ecosystems, Nature Conservation, Environmental Consulting, EIA, Hagat 177, Zichron Yaakov 30900, Israel
Tel. + 972 (4) 6390448; Fax + 972 (4) 6392221; email: einavr@blue-ecosystems.com
“Adan Technical and Economic Services Ltd., POB 18294, Tel-Aviv 61181, Israel
Tel. +972 (3) 5612791; Fax i-972 (3) 5612792; e-mail: adantec@netvision.net.il

Received 10 April 2002; accepted 25 April 2002

Abstract

Processes of desalination of seawater are intended to reduce the deficits in potable water both at present and in
the future. Water desalination processes offer various environmental benefits (related to sanitation, water softening,
quality of sewage effluents), but the process is also accompanied by adverse environmental effects. These effects
can be minimized by the appropriate planning. Most of the effects anticipated would then affect the local environment
in the vicinity of the desalination plants. Desalination may have an impact on five domains: the use of the land, the
groundwater, the marine environment, noise pollution, and finally the intensified use of energy. The impact on land
use is caused by the use of the coastal land for the purpose of building factories, thus converting the coastal area into
an industrial zone instead of an area of tourism and recreation. The impact on groundwater mainly occurs ifpipelines
carrying seawater or brine are laid above an aquifer. It also occurs in the case of feed drilling. In such cases the
aquifer may be damaged either by infiltration of saline water or by disturbances of the water table. The impact on the
marine environment takes place mainly in the vicinity of the concentrated brine discharge pipe. Even though the
concentrated brine contains natural marine ingredients, its high specific weight causes it to sink to the sea floor
without prior mixing. In addition, chemicals, which are administered to the water in the pre-treatment stages of the
desalination process, may harm the marine life in the vicinity of the pipe’s outlet. The actual placement of the
discharge pipe may also damage sensitive marine communities. Noise pollution: A desalination plant, which is
based on reverse osmosis technology, requires high-pressure pumps, which generate noise. Therefore the plant must
be located at a suitable distance from population centers. Technological means may be employed in order to minimize
noise intensities. A desalination plant may also affect the environment indirectly, such as via the intensified use of
energy by the plant. This increased use of energy results in an increased production of electricity by the respective

*Corresponding author.

Submitted to the EuroMed 2002 conference on Desalination Strategies in South Mediterranean Countries:
Cooperation between Mediterranean Countries of Europe and the Southern Rim of the Mediterranean.
Sponsored by the European Desalination Society and Alexandria University Desalination Studies and Technology
Center, Sharm El Sheikh, Egypt, May 4-6, 2002.

001 l-91 64/02/$- See front matter 0 2002 Elsevier Science B.V. All rights reserved
PII: SOOll-9164(02)01057-3
142 R. Einav et al. /Desalination 152 (2002) 141-154

power station, which in turn results in increased air pollution, pollution by coal dust, thermal pollution, etc. The
severity of these effects differs in different areas according to: a) the hydrogeological nature of the marine body
(bathymetry, depth, tides, waves, currents); b) the biological sensitivity ofthe marine habitat; c) the type of desalination
plant, its size, the required secondary structures and infrastructure. Environmental awareness and preliminary planning
can minimize the adverse effects of the desalination process on the environment.

Keywords: Marine; Environment; Desalination; Brine; Outlet; Intake

1. Introduction residential areas as well as an improvement in

the quality of life of people all over the world.
According to the Bible, the first project of de- The yearly deficit in Israel’s water budget, as
salination was conducted by Moses at the place estimated in 2001, is between 200 and 500 million
of Mei Mara in the Sinai desert, where by in- m’/y. A desalination plant, such as the one to be
troducing a piece of bitter wood into the bitter constructed in Ashkelon, would be capable of pro-
water Moses has turned the previously bitter fluid ducing 100 million m’/y of water (320,000 m3/d),
into potable water. The first scientific report accounting for 20-50% of this deficit. Being the
describing a technology designed for the desali- first in a line of plants to be constructed places great
nation of seawater was published by Thomas responsibility on the planners and on those who
Jefferson, the American Secretary of State, in 1791 approve the plans, to establish proper standards
[ 11.Instructions for operation ofthe technology were that can meet with environmental demands. The
posted on notice boards in every ship, for use in a construction of plants for seawater desalination
case of emergency. During the Second World War, is the preferred environmental option for reducing
hundreds of portable desalination devices were the water budget deficit, but first the environ-
used by the troops of the various armies. In the mental price of such plants should be thoroughly
early fifties, research projects were initiated with researched and taken into account.
the aim of lowering the price of the desalination The common technologies for seawater desali-
process. The incorporation of membrane processes nation are based on two main processes - evapo-
resulted in a major improvement to the technique. ration and membrane separation, as shown in
The increase in the standard of living in the Table 1 [2-4]. In general, all processes of evapora-
developing countries during the second half of tion require large amounts of energy and therefore
the 20th century resulted in an increased demand are suitable only to areas that are rich in cheap
for water for daily use as well as for industrial fuel. The cost of energy is the main production
use. At the same time, clear water, regarded in expense in desalination plants (excluding the
the past as a natural resource, available and cheap, amortization) and the process of reserve osmosis
had turned into a precious commodity. A number (RO) is the most efficient desalination process
of reasons may be given to explain this process: both in terms of energy and costs [5,6]. For this and
growth of the population, wasteful use of water, other reasons reverse osmosis is becoming the
pollution of available water resources, and climatic established and preferred desalination process all
changes related to global warming. At the beginning over the world and in particular in Israel, and
ofthe third millennium, we are facing a revolution therefore most of this paper will be dedicated to it.
in the desalination process, where reasonable costs The process of reverse osmosis is based on the
and a continuous trend of further lowering the costs, fact that in all salt solutions an osmotic pressure
will enable the supply of water of high quality at arises whose magni cxctude is proportional to the
convenient prices, thus allowing expansion of salt concentration. When a semi-permeable
 R. Einav et al. / Desalination 152 (2002) 141-154 143

Table 1
Common desalination technologies [2,3]

Reverse osmosis (RO) Membrane processes, the most common system in use. A semi-penetrable membrane separates
two solutions of different concentrations.
Electrodialysis Membrane processes. A bundle of membranes is placed between two electrodes and an electric
(ED/EDR) field is induced. It is mostly suitable for brackish water and for the remediation of polluted
wells.
Multi stage flash (MSF) Evaporation processes, in combination with power stations. The system includes a series of
compartments. The flow of hot water into a compartment in which there is low pressure results
in the evaporation of part of the water.
Multi effect distillation Evaporation processes, based on the cycle of latent heat when generating steam, usually used in
(MED) combination with power stations.
Vapor compression Evaporation processes based on the principle of a heat pump. Repeated cycles of condensation
distillation (VCD) and evaporation.

membrane is placed between two solutions of disinfection. The discharged brine passes through
different concentrations and osmotic pressures, the turbine, which recovers 3040% of the energy
the difference in osmotic pressures will result in invested by the process pump and is then returned
a flow of solvent (and a tiny part of the solute) to the sea. A secondary system used for periodical
through the membrane, from the less concentrated cleaning of the membranes is installed in each
solution to the more concentrated one. In the reverse osmosis plant.
process of reverse osmosis, the direction of the There are five aspects to the impact of desali-
solvent flow is reversed by exerting external nation plants on the environment:
pressure, higher than the difference in osmotic 1. Adverse effect on land use. As factories are
pressures, on the more concentrated solution. located near the shoreline, seashores serve as the
A reverse osmosis plant consists of a bundle sites for industrial plants and for pumping stations
of membranes placed in a pressure chamber, a rather than for recreation and tourism.
high pressure pump, a turbine for recovering 2. Impact on the aquifer. If a desalination plant
energy from the high concentration brine which is constructed inland in order to minimize the
is discharged from the plant, and a system for the impact on the beach, there is a need for pipes to
pretreatment of the feed water and the product transport the seawater and brine. Leakage from
water. In this process (see Fig. l), the seawater the pipes may result in penetration of salt water
enters a pretreatment system, which contains sand and therefore presents a danger to the aquifer. The
filters, micron filters and a system for chemical aquifer is further endangered if drilling is initiated
dosing. The purpose of this pretreatment system in order to draw brackish feed water.
is to protect the membranes from fouling by dirt, 3. Impact on the marine environment as a result
biological or chemical deposits. The feed pump of returning the concentrated brine to the sea.
generates seawater flow at pressures of 55- Although the brine contains materials, which
80 atm. through the membrane system. The originated in the sea, its high specific weight and
desalinated product water, which has passed through the potential presence of additional chemicals
the membranes, then receives a final treatment, introduced in the pretreatment stage may harm
which includes the adjustment of its reactivity the marine population in the area of the discharge
ratio, the reduction of its corrosivity and its of the brine. The installation of the feed and
144

I Coagulate
/
floccohlte

LAciddosage
I
I------+
b
R. Einav et al. /Desalination

,______
152 (2002) 141-154

7, r---------t

,
:
: Fine cartridge
filter :
!_________!

lChlorinefion1 __._
._......
__*

Feed from sea

-3T
Booster pumps

Brine to sea

.---___________
Treated water tank
----__________-

I------ -----------, ! Posttreatment!

1 RO membrane modules
1
1 ;____________:

Potable water

Fig. 1. General layout of a desalination plant employing reverse osmosis technology.

 R. Einav et al. /Desalination 152 (2002) 141-154 145

discharge pipes may itself be harmful. Layers of 3. Impact on groundwater

sand and clay may suffer re-suspension during Pipes of seawater laid over the aquifer pose a
the laying of the pipes and rocky areas and reefs danger to it as these pipes may leak and salt water
may suffer mechanical blows. may penetrate the aquifer. The coastal aquifer of
4. Impact of noise. Seawater desalination plants Israel extends to most areas along its Mediterranean
require the use of high-pressure pumps and turbines shores and thus lies under most of the potential
for recovering energy, which produces noise. They sites for an inland desalination plant. As a result,
should therefore be located far away from populated the laying of pipes carrying seawater and brine
areas or equipped with the appropriate technologies necessitates the use of proper sealing techniques
for lowering noise intensities. and the installation of detectors, which would stop
5. Intensive use of energy. This has an indirect the pumping in case of a malfunction. The preferred
impact on the environment due to the need to site for a plant is an area where the probability of
increase production of electricity with the well- harm to the aquifer is low.
known related environmental consequences. The supply of feed water from feed drilling is
a reliable technology. Its main advantage lies in
the provision of clean and filtered seawater, the
2. The use of land
significant reduction in the danger of pollution,
The environmental value placed on the use of and the stable temperature of the feed water. The
land changes from place to place and is dependent use of water from feed drilling also allows for
on the population density and on the public aware- savings in the pretreatment stage. The drawbacks
ness. In many places this value is negligible, but of the system are the danger of disturbing the
in places with limited seashores, such as the State water table and the aquifer. In many cases (for
of Israel, there is a high value attached to each instance in the plant in Ashkelon) this option was
strip of shoreline, which could be used for internal ruled out in advance.
tourism, external tourism and for conservation of
nature. The area required for a seawater desalination
4. Impact on the marine environment
plant (including pumps and holding ponds) is about
25 acres for a plant that produces 100 million m’/y. Most of the impact on the marine environment
In an area smaller than a 1000 dunams it is possible is a consequence of the positioning of the feed pipes
to desalinate 1 billion m3 of water. and the brine discharge pipes. The initial impact
The outline scheme for the development of the during the laying of the pipes is temporary and
coasts of Israel designate limited areas only for confined to the location of the works, but even
heavy industry, no building is allowed within this impact may be significant, especially in rocky
100 m from the shoreline (with a few exceptions). habitats and coral reefs. The severity of the impact
One of the solutions for minimizing the use of is a function of the level of disturbance to the
coastal land when building desalination plants is environment and of the natural sensitivity, which
locating the plants farther inland. This introduces in turn is dependent on the specific nature of the
the problem of using pipes for transporting large habitat and on the specific communities.
amounts of seawater and brine, with the danger The main impact is due to the discharge of the
of pollution to the underlying aquifer from potential concentrated brine to the sea, and its magnitude
leakage. Placing the desalination plant adjacent depends on environmental and hydro geological
to areas with established and operating infra- factors characteristic of the sea: bathymetry, waves,
structure, in the framework of infrastructure unifi- currents, depth of the water column etc. These
cation, will minimize this impact. factors would determine the extent of the mixing
146 R. Einav et al. / Desalination 152 (2002) 141-154

of the brines and therefore the geographical range The types and the amounts of the chemicals
of the impact. used depend on the chosen technology and the
HGpner and Windelberg divide the global required quality of the product water. Chemicals
marine habitats into 15 categories according to their that are likely to be found in the brines include
sensitivities to the effects of desalination plants antiscaling materials, surfactants, and acids used
[7] (Table 2). According to the hierarchy, which they for the lowering of PH. The salts returned to the sea
suggest, the sites most suitable for the construction are identical to those present in the feed water,
of desalination plants are the shores of the ocean but they are now present at a higher concentration.
(No. 1), in regions of high-energy oceanic coasts. In plants of reverse osmosis, the discharge
The most sensitive regions (No. 15) are Mangal, concentration is 30-70%, or 1.3-1.7 times that of
mangrove flats. Because ofthe diversity of species the original seawater. This is a higher concen-
characteristic to them, coral reefs are rated at 13. tration than the one found for MSF plants where
the return ratio is 1. l-l .5 [9-l 11.
4.1. Composition of discharge brines The chemicals used in the pretreatment of sea-
water are mainly [ 12,131:
In all processes of desalination, discharged
l NaOCl or free chlorine, used for chlorination,
brines, the concentration of which is higher than
preventing biological growth (antifouling).
that of the natural seawater, are returned to the
l FeCI, or AU,, used for the flocculation and
sea. The concentrations of the brines are usually
removal of suspended matter from the water.
found to be double or close to double that of
l H,SO, or HCl, used for pH adjustment.
natural seawater [8]. In addition to the high
l SI-IMP(NaPO,),and similar materials, prevent
concentration of salts, this discharge water
scale formation on the pipes and on the mem-
contains various chemicals used in the pretreat-
branes.
ment stage of the desalination, including various
l NaHSO,, used in order to neutralize any
defouling materials. In the case of evaporation
remains of chlorine in the feed water.
plants, thermal pollution is also produced.
All these materials (in concentrations and
amounts which are similar to those used in
Table 2
Sensitivities of marine habitats to desalination plants [7] desalination plants) are approved for use by the
American EPA and most of them are used in
1. High-energy oceanic coasts, rocky or sandy, systems for drinking water. Chemicals that
with coast-parallel current dissolve in seawater may contribute ions identical
2. Exposed rocky coast to the ions already present in the seawater. For
3. Mature shoreline (sediment mobility)
instance, sulfuric acid increases the concentration
4. Coastal upwelling
5. High-energy soft tidal coast ofthe SO, ion from 3020 to 3050 mg/l, an increase
6. Estuaries and estuary-similar of about 1% above the natural concentration of
7. Low energy sand-, mud- and beach rocks-flats seawater (based on technical information from the
8. Coastal sabkhas Hydranautics company and its rodesign simulation
9. Fjords package). Cleaning of the membranes is conducted
10. Shallow low-energy bay and semi-enclosed
3 or 4 times a year, and the chemicals used are
lagoon
11. Algal (cyanobacterial) mats mainly weak acids and detergents (citric acid,
12. Seaweed bay and shallows sodium polyphosphate and EDTA which is used
13. Coral reefs in order to remove carbonate deposits). The rinse
14. Salt marsh water is kept in a titration container and after being
15. Mangal (mangrove flats) treated (titration, neutralization of the cleaning
 R. Einav et al. / Desalination 152 (2002) 141-154 147

materials), it is disposed off either by transporting logy is required in order to insure the proper dis-
it in closed containers to an authorized salt persion of the concentrated solutions and thus
disposal site, or by the continuous flow of small minimize their adverse effects on the marine
quantities together with the discharged brine back environment. Several alternative techniques are
to the sea. The high dilution ratio (about fifty to available for this purpose, and the choice between
one million) ensures very low concentration of them would depend on the particular conditions
rinsing materials in the brine returned to the sea. in the area, taking into consideration the environ-
Tables 3-5 show some estimates regarding the mental, engineering and economical aspects. The
materials, which would be returned to the sea in alternative techniques are:
the planned desalination plant in Ashkelon [ 121. l Discharging the brines by a long pipe far into
the sea.
l Direct discharge of the brines at the coastline.
4.2. Dispersion of the concentrated saIts
l Discharging the brines via the outlet of the
The major environmental problem associated power station’s cooling water
with a desalination plant is how to get rid of the l Directing the brines to a salt production plant.
surplus of concentrated brines. In most cases,
these brines cannot remain on land because of 4.3. Discharging the brines by a long pipe far
the danger they pose to the underlying ground- into the sea
water and because of other potential and severe
The brines, which would be routinely returned
environmental impacts. Anatural disposal site for
to the sea, would form a plume of highly saline
these brines is the sea, but an appropriate techno-
seawater, corresponding to their amount and to
the conditions of the sea (depth, bathymetry,
Table 3
currents, etc.). The plume would sink to the sea
Flows of seawater and brine

Table5
Feed - Dischargebrine returned
Cleaning and rinsing of the membranes
seawater to the sea (including
rinse water)
Yearly amount, Storage volume,
Hourly flow, m3 13,000 6,750 t m3
Concentration of 40,500 77,920 Citric acid 70 30
salts, mg/l SOdiUIIl 50 20
Total amount of 526 526 tripolyphosphate
salt, t/h EDTA 30 10

Table 4
List of chemicals and the amounts used in the pretreatment stage

Chemicals Doses, Flow, Daily Accumulated volume

mg/l kg/h amount, t (diluted material), m3
Sodium hypochlorite 6 80 1.9 120
Sulfiuic acid 98% 30 390 9.4 100
SHMP (scale remover) 6 80 1.9 120
Iron chloride - flocculant to treat suspended colloids 4 50 1.2 120
Sodium bisulphate 4 50 1.2 120
148 R. Einav et al. /Desalination 152 (2002) 141-154

floor and its effects would extend over a range of and increase the volume of seawater in contact
hundreds of meters. with the brine, therefore improving the mixing.
As this presents a continuous and cumulative The success of the diffusers operation depends
source of pollution, it would result in a continuous on their number and on the space between them.
damage to the biota within the plume’s vicinity. It is possible to improve the dispersion efficiency
It is therefore desirable to place the point of brine by using special diffusers, such as Red Valve
discharge far away from the beach and from rocky diffusers. These boost the brine pressure at the
areas which are rich in organisms, as well as far outlet of the discharge pipe and thereby improve
away from areas where large numbers of people the dilution. Another option is the use of diffusers
are involved in activities such as recreation, touring, directed at an angle of 30-90° to the sea floor, so
fishing etc. that the concentrated brine is pushed in the direction
Most of the data in the literature and most of of the surface of the sea.
the practical experience regarding the flow of The main effects on the marine biota would
liquids into the sea is related to various forms of be in the vicinity of the discharge pipe and would
sewage discharge, where the effluents float on the be related to the increase in the concentration of
seawater because of their lower densities. These salt. This would mostly affect benthic organisms
forces of buoyancy are important in the dilution dug in the sandy bottom as well as planctonic
process of water jets [ 141 but do not exist in the organisms. The salinity is expressed in weight of
case of concentrated brine discharge. The process salts per 1%0and in most seas and oceans its value
of brine dilution is a combination of two physical varies between 32-38%0, which is the range to
processes: the primary (jet) dilution and the natural which most marine creatures have adapted. The
dilution. eastern part of the Mediterranean is more saline
The rate of the jet dilution process depends that its western part [ 171.In the Red Sea salinities
on the difference in densities (a function of the may reach a value of 4 1%o.
concentration of salts and of the temperature) Marine organisms exist in an osmotic balance
between the concentrated brine and the seawater, with their environment and an increase in the
as well as on the momentum, the rate of the flow concentration of salts in this environment may
and the velocity at the outlet of the discharge pipe. result in the dehydration of cells, decrease of the
The jet dilution is further affected by the diameter turgor pressure and death (mainly of the larvae
of the discharge pipe and by the depth of the sea and young individuals). The biomass in Israel’s
floor. In the case of brine, the water jet descends Mediterranean coasts is composed of species,
to the bottom and the effectiveness of this stage which have originated from Pacific and Atlantic
is reduced. Appropriate planning of the discharge species. The Atlantic species, found in the Eastern
pipe, such as the incorporation of diffusers directed Mediterranean, are at the limit of their tolerance
upwards, may improve the jet dilution process to the water salinity, while species that have
[15,16]. originated in the Pacific can cope more easily with
The second phase is the natural dilution (turbu- an increase in salinity.
lent dilution), which takes place following the jet The sensitivity to the increase in salinity varies
dilution stage, mainly as a result of processes of from species to species. To the best of our know-
diffusion and mixing which are generated by ledge, no systematic research has yet been conducted
marine currents and waves. It varies according to on the tolerance of the various species in our region
the marine conditions. to variations in salinity. Some of the planktonic
Installation of diffusers on the discharge pipe algae, and in particular the siliceous ones, can
boosts the turbulent dilution. The diffusers enable tolerate high salinities (these species appear in
the increase in the pressure ofthe entering solutions coastal salt marshes, such as the Bardawill), but
 R. Einav et al. /Desalination 152 (2002) 141-154 149

most of the species will not survive. Certain species completed a few months prior to the writing of
are able to tolerate higher salinities after a period this paper. It is intended to produce 54,000 m3 of
of acclimatization, but the nature of the discharge water daily and a similar amount of brine. Following
flow would not enable the foundation of a population the experience in Dhkelia, the Cyprus Department
of halophile species at the outlet of the discharge of Fisheries demanded that a discharge pipe of
pipe. 1 km length at least would be provided, with its
The sensitivity of the invertebrates, mainly that outlet at a depth of more than 10 m below sea
of crabs, varies but in general it is found that long surface. The existing pipe is 1500 m long and is
abdomen invertebrates are more sensitive to an located 25 m below the surface. The suction feed
increase in salinity than short abdomen ones. The pipe is 1100 m long and is located more than 2 km
larvae of crabs and of other invertebrates, which away. According to Marina Argiro (Cyprus Depart-
float in the water, are more sensitive than the adults ment of Fisheries), the first measurements con-
to changes in salinity [ 1S-2 11. ducted in the site point to good dilution conditions.
Data from systematic monitoring of the dis- An impressive study carried out in the Canary
persion of concentrated brines in marine outlets Islands was presented in a conference that took
is scarce, and the only information we have available place on the 28-3 1 of May 200 1 in Cyprus. The
is from Cyprus and the Canary Islands. Two work included both a survey and the monitoring
desalination plants operate in Cyprus: the plant of the dispersion of concentrated brines past the
in Dhkelia, which has operated for 4 years and the outlet of the discharge pipe, and the influence on
new plant in Larnaca, which has operated for a the marine flora [27]. The research was carried out
few months only [7,22]. at the plant of Maspalomas II. The plant produces
about 17,000 m3/d (about 10% of the amount ex-
4.3.1. The plant in Dhkelia pected in the plant ofAshkelon). The discharge pipe
is 300 m long, its diameter is 60 cm and the water
The length of the discharge pipe is only 250 m.
depth is 7.5 m. It should be noted that the topo-
The suction feed pipe is only 200 m away from
the outlet of the discharge pipe and extends 150 m graphic structure of the sea floor in the area is
into the sea. The Cyprus Department of Fisheries characterized by a shallow shelf extending out a
monitors the site. An increase in salinity within a few meters followed by a steep fall off. The sea
range of 100-200 m from the outlet of the discharge in the region of the island is often rough, and the
pipe has been reported [23-261. In a dive performed tide rises about 2 m. The measurements were con-
on March 7, 1999, around the area of the outlet ducted by divers under calm conditions of the sea.
of the discharge pipe, an impact to the life of the Even though dilution was satisfactory at the surface
littoral fauna and the flora was observed, as wit- of the sea, sinking of concentrated and dense
nessed by the disappearance of certain species from solutions to the bottom was still observed. In
the littoral due to the increased salination in that measurements that were conducted later in the
area. region of the plume, a concentration of more than
60% was detected at a distance of 100 m from
4.3.2. The plant in Larnaca the outlet, and as a result other regions within the
plume are to be monitored. The plume took an
The plant in Larnaca was built by the IDE and elongated form, resembling a salty underwater
Oceana companies. At present it is owned by IDE, river flowing in the direction of the fall line.
which will remain the owner for the next 10 years, Impacts on the local marine flora in the vicinity
at which point the ownership will be transferred of the outlet were observed.
to the government of Cyprus. The plant was
150 R. Einav et al. /Desalination 152 (2002) 141-154

4.4. Direct discharge of the brines at the coastline combined with power stations. The concentration
of brines at the outlet is lower than the discharge
The alternative of discharging concentrated concentrations in plants of reverse osmosis. There
salt solutions directly at the coastline is not is now a tendency there to change to RO plants.
recommended by the authors of this paper, although The country lacks general environmental awareness
under certain conditions (small plants, insensitive and the concentrated brines are discharged into
shore) it should be given some consideration the sea [28].
because of economical factors. Brine water, which In Qatar there is a number of large desalination
is continuously returned to the sea, will form a plants in operation, utilizing both reverse osmosis
plume of high salinity seawater, depending on the and evaporation technologies (MSF). Large
marine conditions and other factors. The effect amounts of brine are generated and there is also
will be noticeable at distances of hundreds of an associated increase in temperature, but the
meters from the outlet (depending on the amounts concentration of salts is relatively low. There is a
of the brines). Even if the brines would be mostly general lack of awareness as to the environmental
diluted at a short distance from the outlet, during effects of the brines. In an essay describing the
the many days in which the sea is calm (such as environmental effects of the plant [9], the marine
during easterly winds), the secondary dilution inlets and outlets are described. The outlets are
would be negligible. On those days the damage located near the coastline, and therefore in order
to the coastal habitats would be high. This method to enlarge the plant it became necessary to build
is not recommended for seas with high sensitivity, a 2 km long feed suction pipe for phase B of the
or for large desalination plants, or for areas with plant.
population of high environmental awareness. An interdisciplinary study was conducted in
In Malta there is a desalination plant that has Florida, USA, aimed at checking the effects of the
been operating for many years. The plant dis- discharge of concentrated brines (and sometimes
charges the concentrated brines directly into the of hot water) from various outlets [29,30] on the
sea, but dilution with seawater is fast due to the environment. The plants which were studied were
great depth (27-30 m). To the best of our know- small scale ones, the largest plant producing
ledge, no environmental survey was conducted 5500 m3/d and most of the other plants produced
in the region (personal information, Domovic much less. The highest salinity of brine measured
Darko). was 39 ppt as compared with a background salinity
In Saudi Arabia there are several large-scale of 35 ppt. The tide in the area varies between values
desalination plants in operation (quoted as producing of l-l.5 m. In most instances the concentrated
one billion m3/d) but the general environmental brines were discharged directly into the sea, but
awareness in the country is very low. The concen- in some cases discharge was accomplished using
trated brines are discharged directly into the sea a short discharge pipe. The population of inverte-
and contain chemicals from the pretreatment stage brates (foraminifera), fish and seaweeds were
as well as membrane cleaning materials. The monitored and so were the salinities along cross
brines are carried away by the tide and by the sections of 10 m length (in varying directions), both
marine currents. We estimate that the depth of along the sea floor and at sea level. There was no
the sea is greater than that of the Mediterranean, preliminary inspection of the study area and no
and therefore the dilution is faster (personal comparison with a control population. According
information, Nicos P. Isaias and Gerhard L. Schanz). to the researchers, no significant changes were
In Kuwait there are a number of large and noted in communities of biota along the sections.
energy costly desalination plants that are based Higher concentrations of salt were found in the
mostly on the evaporation processes and are direction of flow.
 R. Einav et al. /Desalination 152 (2002) 141-154 151

4.5. Discharging the brines via the outlet of the on reverse osmosis and produces almost 12
power station’s cooling water million m3 of desalinated water each year. Part of
the feed water is brackish water from drilled wells
This option suggests using the hot water dis-
(9 million m3 in concentrations of 3500-6000 mg
charged from the power station for the dilution of
chlorides per 1)and the rest of the feed is seawater.
the concentrated brines. The main environmental
The concentration of the brines generated from
advantage is the high dilution ratio achieved. An
the brackish water is 70% and the brines generated
additional advantage lies in the relatively low
from seawater reach a concentration of 50%. The
specific weight of the hot water, which would
brines exit the plant at concentrations that are 2.0-
partially offset the high specific weight of the
2.5 times higher than the concentration of seawater.
brines and would therefore reduce their tendency
The brines are then transferred from the plant to
to sink to the bottom.
the Salt Company ponds and any surplus (the
The combination of a power station and a
amount of which varies with the varying seasons),
desalination plant holds many advantages, though
is transferred to the Eilat bird watching center. At
most of these are relevant to plants that are based
the grounds of the center the brines are combined
on the various evaporation systems and not to
with brines from other sources (the fish growing
reverse osmosis plants [6,28, 3 l-331.
farms, seaweed growing plant), and are then
Calculations made in Ashkelon and Hadera
indicate that the total salinity of the water at the transferred in an open canal to the sea. As the canal
passes through an area, which is a highly saline
vicinity of the outlet of the discharge pipe would
increase by I to 5%. According to the available marsh, and as the flow is by a strong current, it
models for dispersion [34,35], the effect of the seems that there is no penetration of brine water
added brine will disappear at a distance of a few into the groundwater. The canal’s outlet is located
meters from the outlet. In terms of environmental in the northern beach area and to the best of our
considerations, the preferred mode of operation knowledge the rate at which the brine disperses
using this alternative would be to use the existing in the sea has not been monitored (personal infor-
outlet and monitoring system of the cooling water mation, Rafi Iphargan).
of the Electricity Company so as to avoid an added
impact to the marine environment. 5. Noise pollution
A seawater desalination reverse osmosis plant
4.4. Directing the concentrated brines to a salt
is a noisy plant. Most of the noise is produced by
production plant
the high-pressure pumps and by the turbines used
This option, whereby the salts pumped from for energy restoration [36,37]. The impact of the
the sea are utilized for salt production rather than noise does not allow for the operation of a large
returned to the sea, presents many environmental desalination plant in the vicinity of a population
and economical advantages. Its only drawback is center without the use of technological means.
the small number of salt producing plants found Means for decreasing the noise level include the
in the vicinity of desalination plants. If using this building of canopies over the pumps and the
technology, there would be an advantage to the appropriate acoustical planning of the plant.
additional reprocessing of the brines through the
membranes, thereby increasing the salinity of the
discharged water. 6. Intensified use of energy
This option is partially employed in Eilat. The The intensified use of energy by the desalination
Mekorot plant in Eilat (which in the past was plant results in indirect environmental impacts,
based on the Zarchin system) is based nowadays since the energy requirements of the plant increase
152 R. Einav et al. / Desalination 152 (2002) 141-154

the production of electricity, the burning of fuels a. Improvement in quality and sanitation -
and in turn the boost the process of global warming. by adding to the genera1 water supply water that
The energy required to desalinate a m3 of water is free of pollutants, carcinogenic materials, organic
varies from one plant to another and from techno- materials, viruses as well as of offending colors,
logy to technology, and the reverse osmosis tech- tastes and scents.
nology is the most energy efficient. b. Softening of the water-the advantages to
Based on various publications, it is estimated the average household from the softening of water
that the amount of electricity required to produce include prevention of clogging of water pipes,
1 m? of water varies between 3.5-4.5 kWh/m3. prevention of scale formation in boilers and kettles,
We estimate the optimal value to be 4.5 kWh/m3. improvements in laundry and dish-washing effici-
The amount of coal needed to produce one kWh encies, etc. The advantages to the industry include
is 353.8 g. The corresponding amount of crude savings on water softening expenses, economizing
oil (which varies from plant to plant) is approxi- the use of anti scaling materials, etc. The softening
mately 234.9 g for one kWh. (this data provided of water also reduces the need for detergents and
courtesy of Dr. Michal Perla, Electrical Company). this reduced usage would improve the quality of
A plant producing 100 million m3/y water would sewage water.
require an electrical output of SO-60 MW. c. Advantages to the agriculture and the envi-
ronment - the use of treated wastewaters which
contain high concentrations of dissolved salts,
7. Conclusions
sodium, chloride and boron, harms agricultural
The processes of desalination as a source for growth and especially harms sensitive crops. This
potable water are about to become more wide- use damages the soil, interferes with proper
spread. Our duty as citizens and as planners is to drainage, causes the accumulation of salts in the
be aware of the environmental aspects related to substrata, and even damages the underlying
the various processes and in each case to consider groundwater. It has been observed that salination
the environmental costs as well as the require- has already damaged the aquifer and a large
ments and the financial costs. number of wells have already been shut down.
In a paper, which deals with the problems Any damage to the soil, to the crops and to the
caused by processes of desalination, it is also groundwater brings with it further damage to the
important to address the numerous advantages, environment and to the economy. The Israeli
both direct and indirect, of adding desalinated quality requirements of the product water from
water to the existing water system. The main purpose desalination specify an upper limit of 0.4 mg/l
of seawater desalination is to offset present or for boron, so that the product water is bound to
future deficits in potable water, by producing water be low in salinity, and thus the concentrations of
of good quality at a reasonable price. However, chloride and sodium would be lo-100 mg/l. In
the amounts and the quality of the produced water addition, there is the potential for a decrease in
highlight several additional environmental advan- the amount of salts that are now being added to
tages. These advantages are dependent on the urban sewage due to the softening of industrial
intended point of use of the desalinated water as and domestic water. Thus desalination is expected
well as on the volume and quality ratio between to reduce the salinity of treated wastewater, with
this water and the rest of the water in the water all the related implications, including the ability
supply system. to make intensive use of treated wastewater in
The added environmental advantages of the various agricultural applications and even as potable
use of desalinated water are: water. The only way to insure the preservation of
 R. Einav et al. /Desalination 152 (2002) 141-154 153

natural water systems is by the addition of artificially [61 T. Altman, New Power and Water Co-generation
produced water for domestic and industrial use. Concept with Application of Reverse Osmosis (RO)
Desalination, Salzgitter Anlagenbau GmbH, 2000.
A balanced environmental evaluation of the 171 T. Hbpner and J. Windelberg, Elements of environ-
processes of desalination will take into account mental impact studies on the coastal deslination plants,
the extent to which the population requires the Desalination, 108 (1996) 11-18.
water, the ability to allocate water for agricultural, PI C. Vanhems, Critical Review of Desalination Concen-
industrial and nature preservation needs, as well trate Disposal to Surface Water, USA, 1992. (after
UNEP, 2001).
as the need for drinking water.
PI A.J. Morton, I.K. Callister and N.M. Wade, Environ-
A balanced environmental evaluation of the
mental impact of seawater distillation and reverse
processes of desalination will take into account the osmosis processes, Desalination, 108 (1996) l-10.
level of sensitivity of the corresponding environ- DOI R. Zimmerman, DhekeliaDesaIination Plant, Environ-
ment, both marine and terrestrial, to the environ- mental Impact Assessment, 1996.
mental impacts of the desalination plant, and the 1111 R. Zimmerman, The Lamaca seawater desalination
costs of minimizing these impacts. plant, Environmental impact Assessment, 1999.
A balanced environmental evaluation of the WI A. Zfaty, Report submitted to Israel Water Commis-
sioner, 2000 (in Hebrew, ADN5787).
desalination processes will take into account the
economical and environmental costs of the various [I31 K. Harussi, M SC.Technion, Ha& 1997 (in Hebrew).
[I41 UNEP, Assessment of the State of Pollution of the
technologies for acquiring water, such as (deep) Mediterranean Sea by Zinc, Copper and their Com-
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By employing intelligent planning and the Tech., 38(10) (1998) 269-275.
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the adverse effects of seawater desalination plants 523-530.
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1171 O.H. Oren, Seasonal changes in the physical and
of the planners, the designers, the decision-makers chemical characteristic level of the Mediterranean
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and construction, will enable the construction of Jerusalem, 1970.
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P91 J.S. Levinton, Marine Ecology. Prentice-Hall, Inc.
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