Ion exchange is a method widely used in household (laundry detergents and water filters) to produce soft
water. This is accomplished by exchanging calcium
Ca2+ and magnesium Mg2+ cations against Na+ or H+ cations
In reverse osmosis,
pressure is applied to the compartment with high TDS (Total Dissolved Solids). There are two forces influencing the movement of water: The pressure caused by the difference in solute
concentration between the two compartments and the externally applied pressure.
Other systems of water softening