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Desalination and Reverse Osmosis
Koh Huai Ze (10)
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What is Desalination?O The process of removing salt and
other minerals from water
O Water is desalinated in order to convert salt water to fresh water so that it is suitable for human consumption
O Very costly as it requires large amounts of energy and specialised infrastructure
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Methods of DesalinationVacuum Distillation
O The boiling of water at a much lower temperature than normal, saving energy
Reverse OsmosisO Uses membranes to desalinate, applying
reverse osmosis technology O Uses semi-permeable membranes and
pressure to separate salts from water O Less energy is used compared to thermal
distillationO Also used to purify fresh water for medical
and industrial uses
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Reverse Osmosis Desalination Plant
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Reverse Osmosis
In normal osmosis:O Water molecules move from a region of
higher concentration to a region of lower concentration through a partially permeable membrane
In reverse osmosis:O Water molecules are forced to move from a
region of lower concentration to a region of higher concentration by applying a huge amount of pressure
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Reverse Osmosis
Result:O The solute is retained on the pressurised
side of the membraneO The pure solvent is allowed to pass to the
other side
Membrane used:O Designed to only allow water molecules to
pass throughO Does not allow larger molecules such as salt
ions to pass through
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Reverse OsmosisO The pressure applied must overcome
the natural osmotic pressure.O Eg. 600-1200 psi of pressure must be
used for seawater, as it has a natural osmotic pressure of 390 psi.
*Osmotic pressure: The tendency for the solvent to flow through the membrane until there is the same concentration of the solvent on both sides of the membrane
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Process of Reverse Osmosis
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Reverse Osmosis - NEWater
O In 2002, Singapore announced that a process named NEWater would be a significant part of its future water plans
O Involves using reverse osmosis to treat domestic wastewater before discharging the treated water into the reservoirs
O Currently meets 30% of Singapore’s total water demand
O Projected to meet 50% of Singapore’s future water demand by 2060
O Involves advanced dual membrane and ultraviolet technologies
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NEWater PlantNEWater
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Hope you have learnt something from this
THANK YOU