In reverse osmosis processes, the degree of removal of dissolved salts from the feed water as it passed through a semi-permeable membrane (also called "salt rejection"); expressed as a percentage of the feed water TDS. (See total dissolved solids.)
In a membrane system is expressed as a percent of the total presence of those contaminants that are larger than the membrane's pore size and are retained by it or repelled by an electrical charge.
The percentage of TDS removed from the feed water. Typically greater than 90% rejection is achieved with reverse osmosis.