Whenever two solutions are separated by a cell wall (Membrane), a natural transport mechanism take place called osmosis. During osmosis, The solution of lower concentration tends to migrate through the membrane wall which allow the solution to pass, while rejecting the total dissolved solids into the solution of the higher concentration until the two solutions are in the equilibrium. In reverse osmosis, artificial pressure is applied on the concentrated solution side of the membrane, thus forcing water to migrate through the membrane wall into the less concentrated solution.
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