Reverse osmosis is a water treatment process that involves forcing water under pressure through a semipermeable membrane to remove salts, bacteria and other particles from the water. It has become an increasingly popular method of wastewater treatment due to its ability to remove nearly contaminates from water effectively and efficiently.

In a reverse osmosis system, untreated wastewater enters the top of a pressurized tank containing a semi-permeable membrane. The contaminants in the wastewater are too large to pass through this membrane, so they are retained by it while the clean permeate passes out of the other side of the membrane into a separate collection chamber. Diffusion and pressure gradient forces draw clean water molecules across the membrane, and these can then be collected for reuse or disposal.

This method has become popular for treating wastewater since it does not require complex or costly pretreatment systems compared with other options such as ion exchange or adsorption. In addition to removing contaminants from wastewater, reverse osmosis can also lead to more energy-efficient treatment processes by decreasing chemical usage and reducing pump times as well as eliminating additional filtration steps required with some other methods.

Due to its effectiveness, reverse osmosis has been implemented at many different scales including industrial operations where it is used to treat hazardous waste streams, municipal plants where it is used to separately reclaim recoverable resources (such as phosphorus) prior to reuse or disposal, and small scale applications in homes where it helps ensure safe drinking water. Furthermore, improvements in membrane technology have made reverso osmosis increasingly feasible for treating even highly contaminated wastewaters.