The diagram below shows how salt is removed from seawater to make it drinkable. Summarise the information by selecting and reporting the main features, and make comparisons where relevant.

The diagram illustrates a cyclical process where it is explained as an industrial method to purify

salt

water

, making it drinkable.

Overall

, the process is composed of two stages, starting with the extraction of

water

from the

sea

and ending with drinkable

water

stored ready for human consumption. Looking at the first step,

salt

water

is removed from the

sea

, experiencing a pretreatment filter, where

water

may be forced to go through the membrane at high pressure or could be returned to the

sea

via filter backwash. When

water

passes through the membrane, impurities and

salt

are removed from the

water

molecules, which go to the next step.

However

, seawater concentrate with high rates of impurities and

salt

is returned to the

sea

. During the second step,

water

experiences a post-treatment where it is combined with lime, chlorine and fluoride to be

then

stored, ready for consumption.

Finally

, when drinkable

water

is required, it is integrated into the

water

supply system.

This

process is cyclical, removing

salt

water

from the

sea

when it is demanded and purifying it.