Reverse Osmosis Desalination: A Feasible Alternative For Potable Water SupplyRecent technology advances are making desalination less energy-intensive and less costly, bringing us closer to a long-sought solution to water scarcity Freshwater is the liquid of life. Without it the planet would be a barren wasteland. The supply of freshwater is finite, but the demand is rising rapidly as world population grows and as global water use per capita increases. Freshwater supplies are not distributed evenly around the globe, throughout the seasons, or from year to year. Fully two-thirds of the world population — 4 billion people — lives within 250 miles of a seacoast; just over half of the world population occupies a coastal strip 120 miles wide, representing only 10% of the earth’s land surface. A solution to the burgeoning use of freshwater would be to tap the almost limitless volume of ocean water and inland brackish water using desalination processes. Reverse osmosis (RO) filtration by means of semipermeable membranes is the leading technology used in drinking water desalination. Advances in reverse osmosis treatment and membrane materials have created systems that typically use less energy than other desalination processes. The key to expanding the use of RO desalination has come down to finding ways to reduce the energy required to overcome the osmotic forces applied to the membrane. These improvements have led to an overall reduction in desalination treatment costs over the past decade. Advancements in membrane technologies continue to lower energy usage and the costs associated with desalination. Developments such as thin-film composite (TFC) membranes with advanced permeability and flux properties have been key to the widespread use of RO for desalination. Continued research and development of new fouling-resistant and energy- efficient membranes is underway. Over the last decade, advances in RO membranes have allowed them to become more permeable, thereby allowing higher flow rates at lower pressures than previously achieved. Higher permeability lowers the power cost for the same amount of filtered water. Advanced materials have reduced fouling rates, resulting in reduced cleaning cost and increased replacement intervals. Other recent work has focused on integrating RO with electrodialy - sis (ED) to improve recovery of valuable deionized products or to minimize concentrate vol - ume requiring discharge or disposal. Possibly the greatest energy savings breakthrough in the last two decades is the result of integrating energy recovery devices (ERDs) into the operation of desalination RO systems. Thanks to ERDs, it is possible to reuse the energy from the concentrate flow. The concentrate is directed to the ERDs, where it directly transfers its energy in part to the feed flow. ERDs include energy recovery turbines, which can provide power savings of 30-40% over standard RO units not equipped with ERDs. Furthermore, in the last decade innovations in pressure exchanger (PX) technology have created increased energy savings of 50-60% over non-ERD equipped RO units. Read more at: http://proddownloads.vertmarkets.com.s3.amazonaws.com/download/72998ff3/72998ff3-9f5f-4c04-834c-a1c00060be8f/original/12_cleanwater_0513_constantine_.pdf Copyright © 1996 - 2013, VertMarkets, Inc. All rights reserved. To subscribe or visit go to: http://www.wateronline.com |