Reverse osmosis is a moderate to high pressure (80-1200 psig) driven process for separating larger size solutes from aqueous solutions by means of a semi-permeable membrane. This process is carried out by flowing a process solution along a membrane surface under pressure. Retained solutes (such as particulate matter and dissolved salts) leave with the flowing process stream and do not accumulate on the membrane surface. The amount of salt and other impurities is often referred to as TDS, or total dissolved solids. The higher the TDS, the more feed pressure that is required.
Membranes are made with various rejection rates for different application. IFM provides membrane polymers to cover the full spectrum of RO pressure ranges. One of these membrane types is the TFC (thin-film-composite) family. TFC-S (“s” for softening_ and TFC-SR (“SR” for selective rejection) are ideal for low TDS or softening type applications. For higher purity permeate, the ULF (ultra-low pressure) line offers high water flux and salt rejection in a 125 psi class membrane.
When salt rejection is paramount, the TFC-HR (high rejection) elements offer 99.5% rejection to sodium chloride. Typically used in brackish water application with up to 2000-5000 mg/L TDS, they operate around 200 psi. when the water is higher in TDS, the XR (extreme rejection) element comes into its own with 99.7% salt rejection and excellent silica and TOC (total organic carbon) removal too.