CEH370 ASSIGNMENT 1 Dr. George Michaelides Mara CHATZIMANOLI
r.n.: 8092
DESALINATION IN CYPRUS INTRODUCTIONWater resources are a key
factor in the development process and in the balance of ecosystems.
The earth is facing major problems, involving their adequacy and
their management, which lead to local conflicts and disturbance of
transnational relations. Key factors of this tension are the
increase in water consumption due to population growth, the
changing circumstances and requirements of life (consumption model)
and the uncontrolled consumption, which is combined with a
productive and developmental model of voracious that seems
indifferent for natural resources. Depending on the quality
criteria and the type of management used, water can be seen as a
natural resource, as an economic asset and as an environmental
element. Compared, however, with other natural resources and with
other economic goods, water has a peculiarity: it is unique and
irreplaceable. Water is thought as a precondition of human
existence and life on the planet and has no substitute in the
development.The management of lasting (sustainable) water resources
is a key aspect of sustainable development. Water resources are not
unlimited. And indeed, in many regions of the world, as well as in
Cyprus, they are not sufficient and it is this insufficiency that
creates the greatest obstacle to development. Worldwide water
consumption for various uses (residential-urban, manufacturing
development, industrial, irrigation-rural), is growing rapidly.
This offer should not be taken for granted, since it has some upper
limits. The living standards in Cyprus, combined with the climatic
conditions of the island, lead to high demand and thus to
inadequate water availability. This implies high costs for the
sustainable management of water resources. The long planning and
rational water pricing may mitigate this cost.In Cyprus, the lack
of water, is one of the most serious problems. This is mainly due
to reduced precipitation during the year and in the uneven
distribution of rainfall in various regions of the island. To solve
the water problem in Cyprus, the State has taken some steps. Some
of them include the construction of dams on rivers with great flow,
the collection of rain water in tanks and the use of pipes to
transport water from areas with high rainfall in areas facing water
problem such as Larnaca, Nicosia, Famagusta, etc. Nevertheless, the
problem was and continues to be vivid, so it was decided to
construct desalination plants, which became the most important
source of potable water in Cyprus. Through this project the
presence of potable water became independent from the weather
conditions. THE DESALINATIONDesalination is the process of
descaling from a saline substance and mainly from saline waters. In
other words, desalination is a method of obtaining potable water
from seawater, brackish rivers and lakes. It is mainly applied in
areas with dry climate, poor drinking water and access to seawater.
The desalination began to grow in the 20th century with the
appearance of the water shortage in many regions of the Earth.As it
is known, 97.3% of global water is sea stocks mixed in large
proportions with various dissolved salts in such form that its use
for drinking or even for industrial processes becomes impossible.
Historically, the idea of desalination dates back to ancient Greek
seamen who applied it during the 4th century BC by the evaporation
of seawater as it has been described by Aristotle. Another
desalination description can be found by an Arab author of 8th
century AC, which is based in distillation. Although desalination
by distillation and evaporation were already known from the ancient
years, they developed on a large scale from the 1960s onwards. The
last 50 years, desalination has turned into a reliable potable
water production technique using a variety of technical processes
(MSF, MED, RO, etc.). Today there are approximately 12,300
desalination units in 155 countries with production of over
46.000.000 cubic meters of potable water furnishing with water more
than 23 million people.DESALINATION UNITS IN CYPRUS The prolonged
drought that occurred in our region during the last decade of the
20th century, which resulted in unsatisfactory water storage in
dams that were already built, imposed the establishment of
desalination plants of seawater in order to distinguish the
percentages of rainfall from the presence of potable water in urban
and touristic centers. Initially, the desalination plant at
Dhekelia was built.This started working in April 1997 and had a
capacity of 40,000 cubic meters of water a day. This unit serves
the domestic water needs of Famagusta and partially the needs of
Larnaca and Nicosia. The unit since July of 2008 has added 10,000
m3/day and since April 2009, 10,000 m3/day were added to that
reaching today the total production of 60,000 m3/day.The Larnaca
Desalination Unit started working in June 2001 and had a capacity
of 52,000 cubic meters of water a day. The unit was expanded by
10,000 m3/day and since January 2009, its capacity reached the
62,000 m3/day. The Larnaca desalination plant along with the
desalination plant at Dhekelia cover largely the needs of provinces
Nicosia, Larnaca and Famagusta.In December of 2008 the construction
of the mobile desalination unit of Monastery was completed. This
produces 20,000 m3/day. This unit served the needs of Limassol
until the end of 2011. Also, in January 2009 the mobile water
treatment Unit of the river Garylli was completed with a capacity
of 10,000 m3/day covering the the domestic water needs of Limassol.
To meet the needs of the Limassol district for the next twenty
years it was decided to build a permanent unit in the area of
Akrotiri-Episkopi with a capacity of 40,000 m3/day expandable to
60,000 m3/day. To meet the needs of the province of Paphos it has
been constructed on the site of Kouklia a mobile desalination unit
with a capacity of 30,000 m3/day. The unit came into operation in
November 2010 and the duration of the contract was three years. The
construction of a permanent unit in Paphos is under study. The
water development department, (T.A.Y.), has signed an agreement
with the electricity authority of Cyprus (A.H.K.) for the purchase
of desalinated water, from the desalination unit in the area of
Vasilikos. The desalination units consist of:a) Underwater sea
water pipelines and rejection of brine.b) Beach seawater pumping
station.c) Inland pipelines for transferring seawater and dumping
of brine.d) Desalination plant.e) pumping station and pipelines of
desalinated water at TAY tanks.Desalination plants have the
advantage of not depleting water resources and giving good quality
water. Nevertheless, desalination units do not cease to be the most
costly, energy-guzzling and environmentally overcrowded solution
for addressing the lack of water. The sea water is taken from a
point located at a distance of 500-1,000 meters from the shore,
(depending on the prevailing conditions in the maritime area).
Through the pipelines, seawater ends at the pumping station
located on the beach. After passing through dense grids to remove
solids, it is pumped into the unit which is located away from the
beach, about 500-800 meters.( ;; ;;)Importance of desalination
plantsThe confluence of two permanent desalination plants to solve
the water problem plaguing our place is huge. As it has been
already mentioned, the desalination plants in Larnaca and Dhekelia
cover a large part of the need in water in the provinces of
Nicosia, Larnaca and Famagusta. According to current data, the
needs of these three Provinces amounted to 50 CCL water a year. The
two standing units have the ability to produce a minimum quantity
of 40 CCL per year. At the same time, the water problem of the city
and province of Limassol has been reduced with the operation of the
mobile unit in the Monastery and the Garylli. Limassol is fully
independent by rainfall after and unit operation of Episcopi. As
far as Paphos, with the operation of the mobile unit that was
constructed in 2010, it is not facing any problems ever since.
The Larnaca Desalination PlantDesalination MethodsDesalination
methods used today are classified mainly into two categories:
exhaust and methods membrane methods.There are also other methods
that are still in the experimental stage or they are not
advantageous from an economic point of view. Exhaust methods are
being used today only in the oil-producing Middle East countries
that have abundant energy resources, while the rest of the world
mostly uses the method of Reverse Osmosis, which is more
economical.Evaporation or Thermal methods Multistage evaporation
(Multi-Effect Evaporation Distillation ME MED) Multistage flash
distillation (Multi-Stage Flash Distillation - MSF) Evaporation
vapor recompression (Mechanical Vapor Compression-MVC VC) Thermal
vapor compression (Thermal Vapor Compression TVC) . . . . Membrane
Methods Reverse Osmosis (Reverse Osmosis - RO) Electrodialysis
(Electrodialysis ED) Reverse Electrodialysis (Electrodialysis
Reversal - DR)Other methods Ion Exchange Freeze Membrane
distillation Solar gasification Crystallization with hydric ethane
Nanofiltrer (carbon-nanotube membrane).Comparison of desalting
processes
Below, we analyze the method of reverse osmosis, which is the
most widespread.Reverse osmosis (reverse osmosis) The method of
reverse osmosis is the most widely used, reliable and economical
technology for producing high quality irrigation water. The
operating principle of the method is based on a reversal of the
natural phenomenon of osmosis. Normally, when two liquids with
different density (concentration of salts) come into contact, then
the liquid with the lowest density, shifts towards the liquid with
the highest density, until there is a balance (in order for the
whole mixture to obtain the same density). This property is called
Diffusion.However, when a semi-permeable membrane is inserted
between the two liquids, then the passage of salts in blocked, but
this does not occur with water (solvent) which is allowed to flow
freely in the saline solution. The osmotic flow from the thinner to
the denser fluid continues until it reaches a state of equilibrium,
which is characterized by the highest level of saline solution (the
difference in level of solutions corresponding to the osmotic
pressure). This property is called Osmosis. But if we put pressure
on saline, higher than osmosis, then the flow is reversed and we
get clean water from saline to the solvent. This is called Reverse
Osmosis.
Method of Reverse Osmosis In modern applications reverse osmosis
desalination process is automated with a high-pressure pump
continuously to channel seawater in membranes inside a container of
a high pressure (high pressure vessel). The solution feed (feed
water) carved in the Filtrate (purified water) flowing through the
membranes (permeate water) and in high concentration solution
discharged salts, brine or (brine).The membranes are composed of
two distinct layers, the hymen (skin), which is the active part of
the membrane for separation of water from dissolved or suspended
components and by a thin layer of porous material, which is band
pass both from water and from the rest of the ingredients contained
in it. The membranes are made of organic polymeric compounds and is
so thin and fragile, so their formatting is required (with the help
of various studs), in units called membrane components (modules).
The four basic types of membrane elements are the elements of a
helical winding (spiral wound module), the hollow fiber (hollow
fiber module), tubular (tubular module) elements and circular
elements (Platte and frame modules) with the first two types to
have wide-ranging application in desalination. Between the two
membranes, there is a separator membrane of porous material
(usually Pet-Dacron mesh impregnated with resins), which prevents
their union (because of high pressure) and facilitates uniform
water flow between the membranes. The two tips of the membranes of
the open section cling to a centrally perforated pipe from where
clean water is removed (filtrate). Usually the main perforated pipe
is rolled up to form a cylinder, 26 dossiers membranes with
separators that are separated from the plastic grids separating the
power channel of brine. These components of the membranes usually
have a length of 30.5 to 152 cm with a diameter of 5.1 to 30.5
cm.
Three-dimensional visualization of small reverse osmosis units)
Pretreatment: Removed suspended particles and microorganisms are
destroyed in order to prevent their deposition in the membranes.
The pre-treatment consists of an aggregation of colloids,
prechlorination organic substances by adding chemicals, filter
through sand filters and adding sulphate acid to regulate acidity.
Then the filtered water passes through special polypropylene
filters that retain the solid substances with 1mm > size for
reasons of protection of reverse osmosis membranes and follows the
mixed plastics (because the free chlorine destroys the
membranes).b) Reverse Osmosis: high pressure pumps fuel reverse
osmosis membranes with water under pressure 65-80 atmospheres in
order to achieve the passage of water and discard the salts.
Recovery of desalinated water is approximately 45-50% (1 m 3 of
desalinated seawater m3/2) and the remainder (brine) passing
through the pumps where due to high pressure allows the recovery of
25-30% of the original energy. Pipeline then is discharged
overboard to the point that there are currents so there is no
concentration of salts and contaminants.c) finishing: improving
water characteristics (hardness, acidity correcting increase) with
the use of chemicals (processed lime, carbon dioxide or sulphate
acid) into the tank and then sent to the water supply network or
stored.Positives and negatives of desalinationPositive points A
constant supply of good quality water to the public This depletes
water resources, thus helping to environmental sustainability
Indirectly helps in maintaining good quality of inland surface and
underground waters, hence helps in environmental
sustainability.Negative points Has higher production costs than the
usual sources It is energy consuming, so burdens the wider
environment through gaseous pollutants, since the power is produced
by contractual methods. raises the pressure on the marine
environment by placingthe brine Produces noise near the
unitConclusionsDesalination is an important alternative for the
supply of good quality water. It is, also in accordance with the
principles of the water resources management of Directive 2000/60.
The inevitable choice of constructing desalination units has been
proved particularly beneficial for Georgia and salutary for the
water supply in large urban centres. Nevertheless, the construction
of desalination plants is not a panacea. Environmental costs,
mainly because of the gaseous pollutants, must be taken under
consideration, particularly now, with all the threats that our
planet faces. In addition, the economic costs (no recovery) at a
time when the price of oil notes record and shows no inclination to
descend should seriously worry us. The measures proposed to
minimize the negative points, after appropriate environmental
study, include:1. Proper siting of units2. Proper siting of
pipelines of water intake and outlet of brine3. Right duct design
and achieve proper disposal of dilution4. Chemical processing at
outputs5. Measures for noise6. Examining the use of renewable
energy sources
