How does reverse osmosis work and what are its applications?

Reverse osmosis uses semi-permeable membranes and applied pressure (10-70 bar) to overcome osmotic pressure and force water through while rejecting dissolved salts. Pre-treatment (filtration, softening, antiscalant dosing) is critical for membrane protection. Recovery rates are 50-85% depending on feed water quality. Applications include seawater desalination, brackish water treatment, industrial water purification, and tertiary wastewater treatment for reuse. Concentrate disposal is a key challenge.