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separating water from sea water

separating water from sea water. By: Yao David. Contents. Understanding need of pure water First stage of purification Different methods to desalinate sea water Pros and cons for each method Chlorination Graph of whole process References. Water.

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separating water from sea water

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  1. separating water from sea water By: Yao David

  2. Contents • Understanding need of pure water • First stage of purification • Different methods to desalinate sea water • Pros and cons for each method • Chlorination • Graph of whole process • References

  3. Water • Water is a important element in our body. It’s a solvent for most of the solutes in our body. 70% of the mass of our body is due to water! • In the history of man kind, many people have died due drinking contaminated or unclean water because they do not have a source of clean water. • 70% of earth is covered with water and a total of 326 million trillion gallons of water is found on the earth. Even though there is so much water, only 2.5% are fresh water, which are drinkable water.

  4. separation of water • Filtration of water is the act of removing the residue from contaminated water so that this water will be drinkable. As the supply of drinkable water is decreasing, the biggest water source that is not yet drinkable without any form of filtration is the ocean. The ocean contains huge amount of water but as the concentration of salt is huge, the water is not drinkable. In order to obtain more drinkable water, man have come out with many ways to obtain drinkable water.

  5. First stage • In the first stage of purification, a thick layer of sand is used to filter the sea water so as to remove the rubbish and wastes in the water. As the small gaps between the sand particles allow sand to pass through, and leaving the bigger residue on the surface of the sand which will be collected and thrown away.

  6. Methods for second stage • For desalination of sea water, there are different kinds of desalination.The methods are: • Reverse Osmosis • Distillation

  7. distillation • In this method of separating,huge amount of sea water is boiled over a fire. As the water gain heat from the fire, its temperature starts to rise and when it finally boils, the water starts to evaporate. As the water is evaporated, the residues are left behind.

  8. Distillation • The hot water vapour from the mixture will then be channeled through a tube where it will condense when the hot vapourcomes into contact with the cooler surface of the plastic sheet and becomes water droplets which flow does the sheet and clean water will be collected.

  9. Distillation • There are all kinds of distillation which include the following: • 1. Fractional distillation • 2. Steam distillation • 3. Vacuum distillation • 4. Air-sensitive vacuum distillation • There are even more kinds of distillation but which process will help to separate pure water from sea water?

  10. Distillation • The process used for separating pure water from sea water is continuous distillation. In this process, the saltwater is continuously added to the mixture while they were boiling. The mixture is physically divided into two or more product by boiling the product that have a lower boiling point. This process is normally used for chemical process industries as huge amounts of liquids are boiled at the same time.

  11. Distillation-problems • However, as huge amounts of sea water need to be heated, huge amounts of energy will be needed as a continuous heat supply have to be applied to the sea water and this process have to be repeated as more non heated salt water enter for heating. • In order to solve this, scientists have come out with an ingenious method. They changed the pressure above the mixture that needed to be distilled. By doing so, the boiling point of the salt water will be lowered and less heat will be needed to boil the mixture. However, energy still have to be continuously used during this process.

  12. Osmosis • This is the natural process that takes place in cells. Osmosis is the movement of solvents from a lower concentration of solutes to a higher concentration of solutes while passing through a layer of semipermeable membrane. By doing so, the concentration of solutes from both sides will be equalized. • For reverse osmosis, pressure is used to transfer the solvent to the other side of the semi permeable layer.

  13. Reverse Osmosis • As huge amount of energy is still needed for the distillation process, a new more energy efficient way is created. This method is called reverse osmosis. A semi permeable membrane is placed and pressure is applied to the salt water to push them through the membrane. By doing so, the water molecules will be able to pass through the membrane but the salt particles in the water are too big to pass through the water, thus, they will be left behind on the semipermeable membrane.

  14. Pros and cons-distillation • Pros: For distillation, a hundred percent number of salt will be removed from the water as pure water will be evaporated and no salt particles will be collected. By using this process, a pure water can be collected. • Cons: Huge amounts of energy is required for this process compared to the reverse osmosis. Thus, due to this great cost, most people prefer using the reverse osmosis method.

  15. Pros and cons- reverse osmosis • Pros: As pressure is applied to pushed the salt water through the membrane, only minimal amounts of energy is used for this process. Thus, the reverse osmosis is a much commonly used product compared to distillation. • Cons: However, only ninety percent of the residue will be trapped in the membrane. A small amount of salt will still pass the membrane. Thus, multiple layers have to be used to distill the salt water.

  16. Final stage of obtining pure water • Even though the salt particles in the sea water is removed, there is a huge number of bacteria in the water. Chlorine will be added to the water to remove virus and bacteria in the water so that it will be drinkable. This process is called chlorination and it is the final stage of purification of water. After adding chlorine to the water, the water will now be safe for consumption.

  17. Stages of separation Sand filtration Reverse Osmosis Distillation chlorination

  18. Saving water • As we can see, with these methods of purification, man have managed to obtain drinkable water. However, do not take these for granted. In other non developed countries, they do not have the chance to drink these clean purified water. Even though we are getting all the water we want, sooner or later, water might run out on earth, so cherish every glass of water!

  19. References • http://en.citizendium.org/wiki/Continuous_distillation • Helped me to understand more about continuous distillation • http://en.wikipedia.org/wiki/Reverse_osmosis • Helped me to understand more about reverse osmosis • http://en.wikipedia.org/wiki/Osmosis • Understanding of osmosis

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