Environmental effects associated with the production of oil and gas have had significant impacts, including the degradation of soils, groundwater, surface water, and the ecosystems they support by releases of suspended and dissolved hydrocarbons and coproduced saline water. In order to utilize coproduced wastewater for beneficial use, it is necessary to lower the total dissolved solids concentrations of ions that are too high. Tonicity is a measure of the effective osmotic pressure gradient of two solutions separated by a semipermeable membrane. Osmosis is the naturally occurring transport of water through a membrane from a solution of low salt content to a solution of high salt content in order to equalize salt concentrations. Reverse osmosis membranes work on the premise that a pressure greater than the osmotic pressure of the feed solution must be applied to the system to force water through the membrane and reject the salt.