Superfiltration (SF) membranes are a class of membrane that falls between ultrafiltration and nanofiltration. SF membranes demonstrate high NF-like organic rejection and low UF-like inorganic/salt rejection. These have been described as “tight UF”, “open NF”, and “thin-film UF” by different manufacturers. What they all seem to have in common is a molecular weight cut-off (MWCO) between 500 – 3,500 Daltons and low monovalent ion rejection (<50%).
Some SF membranes may have other special properties such as wide pH tolerance or the ability to clean with chlorine, while still others have unique chemistries that offer extremely low fouling on streams that have been considered unsustainable in the past.
With these characteristics, SF membranes can be a great option for applications requiring a separation of components. And because SF is tight enough to remove all oils and grease particulates as well as dissolved constituents that foul and create operational challenges for RO, SF membranes are an excellent candidate for pretreatment to RO in wastewater treatment to purify water for reuse.