Reverse osmosis (RO) is a critical aspect of providing the large volume of relatively purified dialysate water to dialysis patients worldwide. If you’ve never taken a peek at the water treatment room in your hospital’s dialysis unit (it is probably hidden away in a closet or a back room somewhere), I highly recommend it. Although there are now individual-sized RO units available (for example, for use with home dialysis), chances are your hospital’s dialysis unit has a large RO machine (similar to the picture above) installed in order to provide the massive amounts of water needed to power a busy dialysis unit.
Reverse osmosis is the separation process that uses high pressures to force a relatively hypertonic solution through a semipermeable membrane towards a relatively hypotonic solution. Simply put, the hydrostatic pressure exerted on the high concentration side of the membrane must be greater than the osmotic pressure. The same principal may also be used for desalination, the conversion of sea water to drinkable fresh water.