Reverse Osmosis system is the movement process of water from low concentration solution of to high concentration solution due to osmotic pressure. This movement process through semi permeable membrane, where movement process of water will stop after the concentration of two solutions is same. Reverse Osmosis system requires hydrostatic pressure higher than the difference of osmotic pressure so that water can flow from the higher concentration solution through semi permeable membrane.
Reverse Osmosis systems are generally composed of four processes as follow:
Feedwater is first processed to fit the conditions of membrane to remove suspended solids, adjusting pH operations and add inhibitor to control scaling caused by constituents such as calcium sulfate.
- Giving pressure
Feed water that has been processed, its pressure will be increased by the pump up to the desired operating pressure to conform to membrane and feed water salinity.
- Membrane separation
Semi permeable membrane inhibits the course of feed water through it. Water output from membrane produce clean water which is called permeates, and retained on the membrane is called concentrate. However, because there are no membranes that can work 100% perfect, then there is a small part of salt that can still pass through membrane.
Water output membrane (product water) is usually adjusted to pH first before being transferred to distribution system.