Chenab College of Chenab College of Engineering Engineering & & Technology GRWTechnology GRW

Seawater Desalination and Seawater Desalination and Water Supply ReliabilityWater Supply Reliability

Submitted To: Engr. M Bilal Group Members: Usman Ali 2014-uet-ccet-mech-05M. Ahmad2014-uet-ccet-mech-09H. Zahid Ali 2014-uet-ccet-mech-14Qamar Abbas 2014-uet-ccet-mech-15 Subject: Environmental Pollution

OutlineOutline• M. AhmadM. Ahmad IntroductionIntroduction

• Qamar AbbasQamar Abbas MFS & Reverse MFS & Reverse Osmoses DesalinationOsmoses Desalination

• Usman Ali Usman Ali Freezing & Geothermal Freezing & Geothermal DesalinationDesalination

• H.Zahid AliH.Zahid Ali Solar Desalination Solar Desalination

What is Desalination?What is Desalination?Desalination is a process that removes minerals Desalination is a process that removes minerals from saline water.from saline water.More generally,More generally, desalination refers to the desalination refers to the removal of salts and minerals from a target removal of salts and minerals from a target substance, as in soil desalination, which is an substance, as in soil desalination, which is an issue for agriculture. Saltwater is desalinated to issue for agriculture. Saltwater is desalinated to produce water suitable for human consumption produce water suitable for human consumption or irrigation.or irrigation.

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HistoryHistory• Clean drinking water is so widely available Clean drinking water is so widely available

today that many people take it for today that many people take it for granted. In actuality, human beings have granted. In actuality, human beings have taken extensive measures throughout taken extensive measures throughout history to produce clean drinking water.history to produce clean drinking water.

• In the ancient times, people determined In the ancient times, people determined the purity of water by taste, and this the purity of water by taste, and this method has been found to be incorrect method has been found to be incorrect later onlater on

• Old water treatment methods include the Old water treatment methods include the boiling of water over fire, heating of water boiling of water over fire, heating of water under the sun, dipping of heated iron into under the sun, dipping of heated iron into water, filtration through gravel and sand.water, filtration through gravel and sand.

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Why Desalination?Why Desalination?• 75% of the Earth’s surface 75% of the Earth’s surface

is covered by wateris covered by water• 97.5% of that water is 97.5% of that water is

oceansoceans• Only 1% is available for Only 1% is available for

drinkingdrinking• 80 countries suffered from 80 countries suffered from

water water scarcity by the mid-1990sscarcity by the mid-1990s

• 1.5 billion people lack 1.5 billion people lack access access to drinking waterto drinking water

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Desalination TechniquesDesalination Techniques

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Multi Stage Flash Multi Stage Flash desalination desalination •Multi-stage flash distillation (MSF) is a

water desalination process that distills sea water by flashing a portion of the water into steam in multiple stages of what are essentially countercurrent heat exchangers. Multi-stage flash distillation plants produce about 60% of all desalinated water in the world

Multi Stage Flash Multi Stage Flash desalination desalination

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Revers Osmosis Revers Osmosis •Reverse osmosis (RO) is a water

purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pressure.

•The largest and most important application of reverse osmosis is the separation of pure water from seawater

EfEffectiveness of Reverse fectiveness of Reverse OsmosisOsmosis

Revers Osmosis Revers Osmosis

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Freezing desalinationFreezing desalination•Freezing desalination process uses

freezing to remove fresh water from frozen seawater.

•Seawater's freezing point is lower than that of pure water and its boiling point is higher.

• It is easier to float objects in seawater than in fresh water. Many humans can “float” in seawater but not fresh water. Floating refers to having a substance rise to the top of another substance.

Freezing desalinationFreezing desalination

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Geothermal desalinationGeothermal desalination

•Geothermal desalination is a process under development for the production of fresh water using heat energy. Claimed benefits of this method of desalination are that it requires less maintenance than reverse osmosis membranes and that the primary energy input is from geothermal heat, which is a low-environmental-impact source of energy.

Geothermal desalinationGeothermal desalination

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Solar desalinationSolar desalination

•Solar desalination is a technique to desalinate water using solar energy.

Types:_Solar humidification–

dehumidification method (HDH)Multiple-effect humidification

(MEH)

Solar humidification–dehumidification method (HDH)•The solar humidification–

dehumidification method (HDH) is a thermal water desalination method. It is based on evaporation of sea water or brackish water and consecutive condensation of the generated humid air, mostly at ambient pressure

Solar desalinationSolar desalination

Multiple-effect humidification (MEH)•Multiple-effect humidification (MEH)

is a method used for thermal desalination of sea water. It uses multiple evaporation–condensation cycles at separate temperature levels to minimize the total energy consumption of solar humidification processes.

Multiple-effect humidification (MEH)

Factors Increase the water Factors Increase the water consumption areconsumption are• Growing of populationGrowing of population• Growing of industryGrowing of industry• Agriculture/Irrigation needsAgriculture/Irrigation needs

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