Over the past half century, reverse osmosis (RO) has grown from a nascent niche technology into the most versatile and effective desalination and advanced water treatment technology available. However, there remain certain challenges for improving the cost-effectiveness and sustainability of RO desalination plants in various applications. In low-pressure RO applications, both capital (CAPEX) and operating (OPEX) costs are largely influenced by product water recovery, which is typically limited by mineral scale formation. In seawater applications, recovery tends to be limited by the salinity limits on brine discharge and cost is dominated by energy demand. The combination of water scarcity and sustainability imperatives, in many locations, is driving system designs towards minimal and zero liquid discharge (M/ZLD) for inland brackish water, municipal and industrial wastewaters, and even seawater desalination. Herein, we review the basic principles of RO processes, the state-of-the-art for RO membranes, modules and system designs as well as methods for concentrating and treating brines to achieve MLD/ZLD, resource recovery and renewable energy powered desalination systems. Throughout, we provide examples of installations employing conventional and some novel approaches towards high recovery RO in a range of applications from brackish groundwater desalination to oil and gas produced water treatment and seawater desalination.

Dr. Eric M.V. Hoek is a professor in UCLA's Department of Civil & Environmental Engineering, Institute of the Environment & Sustainability and the California NanoSystems Institute. He is also the Director of the UCLA Sustainable LA Grand Challenge. His research explores the union of membrane technologies, nanomaterials and electrochemistry for water, energy and environmental applications. He has over 200 technical publications including over 70 patents filed globally. He has also co-founded several technology startups and has ad vised a wide array of state, federal and international government agencies, local water utilities, technology companies, investment funds, law firms and research funding agencies.David Jassby is an associate professor in the Department of Civil and Environmental Engineering at UCLA. He received his Ph.D. in Civil and Environmental Engineering from Duke University (2011), an M.S. in Civil and Environmental Engineering from UC Davis (2005), and a B.Sc. in Biology from Hebrew University (2002). David spent a year working as a consultant in an Environmental Engineering consulting firm in NC (BBL, Inc.). David’s research is primarily concerned with membrane separations, environmental electrochemistry, and water treatment technologies. His lab is currently engaged in research concerning membrane development, desalination, industrial wastewater treatment, oil/water separations, and the electrochemical treatment of contaminated water. He holds several patents on electroactive membranes and processes, and has published more than 60 peer-reviewed manuscripts in peer-reviewed journals.
Richard B. Kaner is a Distinguished Professor in the UCLA Departments of Chemistry and Materials Science and Engineering and holds the Dr. Hong Endowed Chair in Materials Innovation. His research explores new materials from graphene for energy storage to nanostructured conducting polymers for separation applications. He has published over 425 papers and 45U.S. patents. According to Clarivate Analytics and Thomson–Reuters he is among the world’s most highly cited authors. He has received Fellowships from Dreyfus, Fulbright, Guggenheim, Packard, and Sloan Foundations along with the Materials Research Society Medal, the Royal Society of Chemistry Centenary Prize, the Chemical Pioneer Award, and the American Chemical Society Award in the Chemistry of Materials.
Jishan Wu is a Ph.D. student in UCLA’s Department of Civil & Environmental Engineering, under the supervision of Prof. Eric M.V. Hoek. His research revolves around membrane and other advanced technologies for water applications. He is the lead author of the book Sustainable Desalination and Water Reuse. His Ph.D. thesis focuses on developing novel ultrahigh pressure reverse osmosis (UHPRO) with the objective of achieving minimum/zero liquid discharge more cost-effective and sustainable.
Dr. Jingbo Wang is currently a postdoctoral scholar working with Prof. Eric Hoek and Prof. David Jassby in the Department of Civil & Environmental Engineering at UCLA. She received her B.S. from Wuhan University in Water and Wastewater Engineering, and Ph.D. from University of North Carolina at Chapel Hill in Environmental Sciences and Engineering. Her research interests focus on desalination, water and wastewater treatment with membrane technologies, and application of nanotechnology in membrane separation and other physical/chemical processes in environmental systems.
Yiming Liu is currently a Ph.D. student in the Department of Civil and Environmental Engineering at UCLA. His research with Prof. Eric Hoek is modeling membrane-based desalination processes that enables high water recovery. Yiming obtained his Master’s degree in Civil Engineering from UCLA and his Bachelor’s degree in Environmental Engineering from Tsinghua University.
Unnati Rao is a Postdoctoral Scholar in the department of Civil and Environmental Engineering at the University of California, Los Angeles (UCLA) in the NANOMETER lab under the guidance of Dr. Eric M.V. Hoek. Her research focusses on the development and testing of membrane materials for water treatment. She has also extensively worked in the application of electrochemistry for water treatment processes. She has over six technical publications. She also has a patent and has presented her work in two national level conferences.