Reverse osmosis membrane technology has developed over the past 40 years to a 44%
share in world desalting production capacity, and an 80% share in the total number
of desalination plants installed worldwide. The use of membrane desalination has increased
as materials have improved and costs have decreased. Today, reverse osmosis membranes
are the leading technology for new desalination installations, and they are applied
to a variety of salt water resources using tailored pretreatment and membrane system
design. Two distinct branches of reverse osmosis desalination have emerged: seawater
reverse osmosis and brackish water reverse osmosis. Differences between the two water
sources, including foulants, salinity, waste brine (concentrate) disposal options,
and plant location, have created significant differences in process development, implementation,
and key technical problems. Pretreatment options are similar for both types of reverse
osmosis and depend on the specific components of the water source. Both brackish water
and seawater reverse osmosis (RO) will continue to be used worldwide; new technology
in energy recovery and renewable energy, as well as innovative plant design, will
allow greater use of desalination for inland and rural communities, while providing
more affordable water for large coastal cities. A wide variety of research and general
information on RO desalination is available; however, a direct comparison of seawater
and brackish water RO systems is necessary to highlight similarities and differences
in process development. This article brings to light key parameters of an RO process
and process modifications due to feed water characteristics.