The diagram shows the process of water treatment

Sea

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water

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treatment is a linear manmade process that comprises 4 main stages

according to

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the diagram given.

First,

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the saltwater flows into pipes from the

sea

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to the reservoir where it is preliminarily treated. After it goes

further

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, there are two directions where

this

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liquid flows:

while

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one tube is used to wash it back to the

sea

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through the filter, another one is designed to push the pretreated substance forward to the next stage called treatment. There, the filter consists of a membrane with small circular holes which take in only

water

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molecules but not salt

due to

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its bigger size. To make it possible, high pressure is applied. Before going to the following stage, the unfiltered salt

water

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is returned to the

sea

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through a separate tube. Meanwhile, the purified substance goes to the post-filtration reservoir, where it is handled with chemical reagents (lime, chlorine and fluoride) for additional purification. As soon as the

water

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is post-treated, it is stored for future consumption.