学术交流英语发言稿

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Hello! Everyone! I’m XX. My speech is about reverse osmosis desalination in water governance.



I will carry on the speech from the following respects: First, the background of reverse osmosis desalination. Second, the mechanism of reverse osmosis desalination. Third, the development of reverse osmosis desalination.



If you log on to the Web of Science, and then search for “water governance” and “environmental governance”. Web of Science records 8,070 references to the phrase “water governance” and 13,766 references to “environmental governance”. Water is an unequally distributed, renewable natural resource which is inherently part of the natural environment. However, its use is essential to both social and economic activity. Water governance has been a main part of environment governance and attracted increased attention in recent years.



In 1992, Dublin Conference first reported the issue of scarcity of fresh water. It said that Scarcity of fresh water pose a serious and growing threat to sustainable development and protection of the environment.



Look at the picture of the water distribution of the world, you may raise a question: we are surrounded by the ocean, but why we are still lack of water? It’s because that human cannot directly use seawater, which contain a large amount of salt. Today, I would like to introduce the technology widely used in the world -

reverse osmosis desalination. It can remove salt of seawater and convert seawater into fresh water.



Reverse osmosis describes a reverse process of natural water infiltration in nature. As early as 1950, the American scientist Sourirajan once inadvertently

discovered that a seagull lifted a large mouthful of seawater while flying at sea, then a small mouthful of seawater was spit out after a few seconds. He took the seagull back to the laboratory, and found a thin membrane on the seagull's month. Seagulls use this membrane to filter seawater into fresh drinking water. Concentrated seawater containing impurities and highly salt was spit out of the mouth.



It’s known to us when the same volume of dilute solution and concentrated solution are placed on both sides of a container, with a semi-permeable membrane in the middle, the water in the fresh water will naturally pass through the semi-permeable membrane and flow to the concentrated solution side. This is called

osmosis. Then it can reach osmosis equilibrium with a osmotic pressure. However, if


a pressure higher than the osmotic pressure is applied on the seawater side, it will be different.



The water in the seawater will flow to the fresh water. The flow direction of this solvent is opposite to the original infiltration direction. This process is called reverse osmosis.



Reverse osmosis is the core part of water purifier. It can remove salt and impurities, then bring us fresh water.



After decades of continuous development, the performance of seawater

desalination reverse osmosis membranes has been greatly improved. The water flux is twice of that in 1978, and the salt transmission rate is about a quarter of that in 1978.



Now it is widely used in desalination plant, sewage treatment and water purifier. There are still some drawbacks of our reverse osmosis device, such as the requirement of high-pressure equipment and regular cleaning. Scientists will try their best to solve technological problems, and I do hope that our reverse osmosis desalination will bring fresh water to more regions of the world.

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