About Reverse-Osmosis Water Filters
Reverse osmosis is a fundamental water purification technology. Depending on the water source and the ultimate purpose, it might be the primary technology used. It is widely used in everything from making drinking water to preparing water use for coral reef aquariums. Does this Spark an idea?
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Reverse Osmosis
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Reverse osmosis works by using pressure to push liquid through a membrane. The result is that the desired liquid emerges on the other side in a purer state, and impurities in the liquid solution are left behind, filtering the liquid. This is the reverse of normal osmosis, where the impurities in the solution move from low concentration to high concentration through a membrane with no pressure applied. The reliability of the process makes it very useful for water purification.
Membranes and Water Pressure
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Reverse osmosis can be using to filter water from a variety of sources and the membrane need not be changed. This membrane is typically a thin film composite membrane with a dense polymer inner matrix. What does need to be changed is the amount of pressure applied. Brackish, but otherwise fresh water needs 30 to 250 psi. Seawater, on the other hand, demands 600 to 1000 psi. This is because the amount of pressure applied must overcome the osmotic pressure of the solution in question, and that is much greater for salt-heavy seawater.
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Desalination
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Reverse osmosis is best known as a filtration method in desalinating sea water. Mass desalination is very energy intensive, and is therefore only economical in wealthy countries that have scant water resources, such as in the oil-rich Middle East. 3/4s of the world's desalination capacity is located there, including the single largest facility, the Jebel Ali Plant in the United Arab Emirates. By comparison, the largest plant in the US is in Tampa Bay, FL. It can produce 25 million gallons of fresh water per day, which is about 12 percent the capacity of Jebel Ali.
Drinking Water
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Reverse osmosis is usually one step among many in producing tap water in the developed world. It sits in the middle of sediment and carbon filtration on the one hand, and chemical or ultraviolet radiation treatment on the other.
Industrial Water
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Industrial water needs to be purified so that it does not leave mineral deposits behind on machinery. Reverse osmosis filtration or distillation is usually the best way to achieve this.
Aquariums
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Another important use of reverse osmosis is to prepare water for use in seawater reef tanks at aquariums. Tap water is typically packed with chemicals that are insignificant in most applications, but harmful to the sensitive microorganisms that make ocean corals. Also, the nitrates and phosphates found in tap water promote the growth of algae, which is an unwanted pest plant for aquariums. In this case, reverse osmosis is used to remove these chemicals from common drinking water before making it into salt water.
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