An Introduction To Membrane Techniques For Water Desalination

NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competences and with regard for appropriate balance. Support for this study was provided by the U.S. Bureau of Reclamation under Grant No. 06CS811198. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

Abstract: Texas’ increased interest in desalination reflects a worldwide trend to include it as a viable alternative water supply option in any long-term water strategy. Recent technological developments and new methods of project delivery are driving this heightened level of interest to the point that desalination is now being seriously evaluated on projects where it would not have been considered ten years ago. The most significant trend in desalination is the increased growth of the reverse osmosis(RO) market. Technological improvements have both dramatically increased the performance of RO membranes. Today’s membranes are more efficient, more durable, and much less expensive. Improvements in membrane technology are complimented by improvements in pretreatment technology, which allow RO membranes to be considered on a much wider range of applications. Energy costs are directly related to the salt content of the water source, and may represent up to 50% of a system’s operational costs. There has been a growing trend to reduce energy costs through improvements in membrane performance and by employing modern, mechanical energy recovery devices that reduce energy requirements by 10-50%. The growing trend to build larger desalination plants recognizes the inherent modularity of RO systems and the fact that the development, design, and permitting costs are somewhat independent of plant size. The result is that larger plants are being constructed to take advantage of economies-of-scale, which reduce the unit cost of desalinated water. Other trends that will be reviewed in more detail include the co-siting of desalination plants with electric power generating plants and other industrial facilities, and the hybridization of distillation and membrane processes.