IELTS TASK 1; Making sea water drinkable

The diagram shows how salt is removed from sea water to make it drinkable. There are several steps that take place in this process.

At the first stage, sea water is gone through from sea water intake. Then, it is put into pre-treatment filter. In this filter, some materials in sea water are filtrated and they are returned to sea. After this stage, water forced through membrane at high pressure. While water molecules are passing easily in membrane, other components which are impurities and salt do not pass in it. In this way, salt is removed from water. Then, other components mixed with sea water and this concentrate is returned to sea. After treatment, water is mixed with lime, chorine and fluoride in third phase. With this, seawater becomes drinkable water. After this, it is put into storage. Lastly, drinkable water is integrated water supply system.

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  diag_seawater.jpg
  

.... this is not a natural process, so "sent" is more appropriate. I suggest you to capitalize the device (Salt Water Intake)
After this stage, water is forced through membrane at high pressure.
Overall, this is very good writing :)

dumi thank you

I think you're doing well except some little mistakes.
good luck