Reverse osmosis (RO) is a process in which water is subjected to high pressures through a semi-permeable membrane to separate dissolved solids from water molecules. Reverse osmosis is not a standalone process, however, it is often paired with pretreatment - chemical injection and filtration – for greater quality and better system performance.
Any system is usually composed of the following elements: Raw water tank, (pre) chlorine dosing set, feeding pump, sediment filter, carbon filter, (pre) pH adjustment dosing set, anti-scalent dosing set, micron filter, high pressure pump, semipermeable membrane elements, anticorrosion dosing set, (post) pH adjustment dosing set, (post) chlorine dosing set and a treated water tank.
With a normal system, raw water is transferred from the source (well and/or municipality) to a transfer tank where chlorine is continuously added for contamination and bacterial disinfection. Water is then pumped through the sediment filter to remove large suspended solids and particles. It is then transferred through the carbon filter to remove all chlorine residuals, by-products, and any organic matter. Water exiting the carbon filter is dosed with acid or base to adjust pH levels of the water, and with anti-scalent to prevent residual buildup inside the pipework and membranes. Dosed water is then pumped through the high pressure pump to the membranes for dissolved solids and salt separation. Permeate water is then dosed with anticorrosion, pH adjustment solution, and chlorine before it enters the storage tank, while reject water is wasted.
A reverse osmosis unit does use more water than it produces, but you can think of it as any other water appliance that uses water to clean and maintain itself. As for the amount of reject water, that depends on the salinity of the feed, but under normal conditions, it doesn’t exceed 30-40% of the feed.
Water with high salinity has many negative effects on our lives, it can damage our skin and hair, cause build up and rust in and on water appliances, utensils, and pipework.
Installing a reverse osmosis unit in your house or building will guarantee that you have access to clean water free of bacteria, impurities and excess minerals.
The unit as a whole would last you a lifetime under proper maintenance and operating conditions. However, parts should be serviced and replaced when needed. The operation of the RO is limited by the lifetime of the membrane which is typically 3-5 years, depending on the operating condition.
The process as a whole run on the concept of providing a pressure above osmotic pressure to drive the water through the semipermeable membrane salt-free. In order to provide that pressure, we utilize high pressure pumps which are electrically operated. With large systems, an energy recovery turbine might be installed if it shows to be efficient.