9 Seawater Desalination Plants: Heavy (oastallndustry
93
sponding environmental laws and have founded the corresponding institutions. Above
all, the GCC play an important role in harmonising protection activities and in encouraging local environmental activities. Most recently, the Middle East Desalination Research Centre (Muscat) was founded. It may be expected that it develops to a core institution of cooperation in the interest of environmentally adapted technologies.
Among other arguments, such as avoiding pollution in advance, the application of
EIA serves increasingly as an argument for international financing. Additionally, it helps
to establish a good reputation outside the country and is nowadays a selling promoter
of environmentally sensitive export products such as food or chemicals.
9.3
Coastal Morphological Impacts
The impacts on coastal morphology can be divided into transient and permanent ones.
Transient ones are those bound to the phase of construction. They are not treated here.
Among the permanent ones are morphological changes at the sites of the plants, e.g. the
effects of the seawater intake and concentrate outfall constructions. Since the hydrological and sedimentological dynamics may be affected, the impacts on the coastal ecosystem may be severe.
A large desalination plant with a capacity of 0.3 x 10 6 m 3 of freshwater per day takes
in 2.4 x 10 6 m 3 seawater and releases 2.1 x 10 6 m 3 heated and salt-enriched seawater per
day. The water taken in must be as poor as possible in suspended matter which is achieved
by wide, deep and long channels through which the water flows very slowly and without turbulence. Since water from some distance from the coast is clearer, the channels
extend far into the sea, sometimes for more than 1 kIn. For security reasons sluice doors
are built which can be closed during rough weather and extreme water levels. To avoid
the entering of sea animals, plants and floating objects, grids and sieves are installed.
Taking these requirements together, an intake is a large-scale building exhibiting a severe influence on the coastal dynamics. As a sign of a general re-thinking, Morton
et al. (1996) describe the intake construction of Station B of the Ras Abu Fontas
Desalination plant (Quatar) where the proper intake is located 2 kIn off the coast and
linked to the Plant by pipelines buried in the sea floor.
In contrast, much less expense is usually spent on the outfall. To save money and to
remove the proper outfall as far as possible from the point of intake, natural tidal channels, river mouths, lagoons and mangrove swamps are used to guide the discharged
water away from the intake. The purpose is to avoid recirculation effects between the
intake and the outlet, which clearly is not so easy when the currents change with the
tides and the winds. These aspects caused earlier desalination plants to be located within
tidal channel and lagoon systems rather than at the open coast.
9.4
Some Technical Information About Thermal Desalination
This section is rather to help the reader understand the principles of thermal desalination
than to describe the technical design of thermal desalination plants. For a more extended discussion see Buros (1990). Over 60% of the world's desalted water is produced
with heat to distill freshwater from seawater. For this to be done economically in a
93
sponding environmental laws and have founded the corresponding institutions. Above
all, the GCC play an important role in harmonising protection activities and in encouraging local environmental activities. Most recently, the Middle East Desalination Research Centre (Muscat) was founded. It may be expected that it develops to a core institution of cooperation in the interest of environmentally adapted technologies.
Among other arguments, such as avoiding pollution in advance, the application of
EIA serves increasingly as an argument for international financing. Additionally, it helps
to establish a good reputation outside the country and is nowadays a selling promoter
of environmentally sensitive export products such as food or chemicals.
9.3
Coastal Morphological Impacts
The impacts on coastal morphology can be divided into transient and permanent ones.
Transient ones are those bound to the phase of construction. They are not treated here.
Among the permanent ones are morphological changes at the sites of the plants, e.g. the
effects of the seawater intake and concentrate outfall constructions. Since the hydrological and sedimentological dynamics may be affected, the impacts on the coastal ecosystem may be severe.
A large desalination plant with a capacity of 0.3 x 10 6 m 3 of freshwater per day takes
in 2.4 x 10 6 m 3 seawater and releases 2.1 x 10 6 m 3 heated and salt-enriched seawater per
day. The water taken in must be as poor as possible in suspended matter which is achieved
by wide, deep and long channels through which the water flows very slowly and without turbulence. Since water from some distance from the coast is clearer, the channels
extend far into the sea, sometimes for more than 1 kIn. For security reasons sluice doors
are built which can be closed during rough weather and extreme water levels. To avoid
the entering of sea animals, plants and floating objects, grids and sieves are installed.
Taking these requirements together, an intake is a large-scale building exhibiting a severe influence on the coastal dynamics. As a sign of a general re-thinking, Morton
et al. (1996) describe the intake construction of Station B of the Ras Abu Fontas
Desalination plant (Quatar) where the proper intake is located 2 kIn off the coast and
linked to the Plant by pipelines buried in the sea floor.
In contrast, much less expense is usually spent on the outfall. To save money and to
remove the proper outfall as far as possible from the point of intake, natural tidal channels, river mouths, lagoons and mangrove swamps are used to guide the discharged
water away from the intake. The purpose is to avoid recirculation effects between the
intake and the outlet, which clearly is not so easy when the currents change with the
tides and the winds. These aspects caused earlier desalination plants to be located within
tidal channel and lagoon systems rather than at the open coast.
9.4
Some Technical Information About Thermal Desalination
This section is rather to help the reader understand the principles of thermal desalination
than to describe the technical design of thermal desalination plants. For a more extended discussion see Buros (1990). Over 60% of the world's desalted water is produced
with heat to distill freshwater from seawater. For this to be done economically in a