Membranes to Manage Salinity

Over the past decade, membrane technologies have revolutionized water and wastewater treatment and become more prevalent in water recycling, water reuse, and salinity management. All four major membrane categories (microfiltration [MF], ultrafiltration [UF], nanofiltration [NF], and reverse osmosis [RO]) are commercially available. Membranes have been used extensively in the private sector, but they are still considered cutting-edge technology in the public sector. When water scarcity occurs, three major additional water sources are considered: 1) Water conservation, 2) Recycling, and 3) Desalination. As water conservation has its limits, recycling and desalination may be the most cost-effective additional water sources, and membranes can provide the best way to harness them. In particular, the low-pressure membranes used in bioreactors (MBRs) have significant benefits for both new and upgraded wastewater treatment facilities compared to more traditional treatment processes. For water recycling when salinity has to be addressed, the MBR is a reliable method for doing so as pre-treatment to reverse osmosis (RO), with the added benefit that it does not require any additional equipment. This paper provides a brief history and overview of membranes and addresses their growing use, applications, and challenges, including salinity management.