Osmosis economic interest

Reverse osmosis is now extensively used to reduce salt concentrations in brackish waters and to treat industrial waste water, for example, from pulp mills. Reverse osmosis has also proved economical (the cost can be as low as about 1 per 1000 liters) for large-scale desalination of seawater, a proposition of major interest in the Middle East, where almost all potable water is now obtained by various means from seawater or from brackish wells. Thus, at Ras Abu Janjur, Bahrain, a reverse osmosis plant converts brackish feedwater containing 19,000 ppm dissolved solids to potable water with 260 ppm dissolved solids at a rate of over 55,000 m3 per day, with an electricity consumption of 4.8 kilowatt hours per cubic meter of product. On a 1000-fold smaller scale, the resort community on Heron Island, Great Barrier Reef, Australia, obtains most of its fresh water from seawater (36,000 ppm dissolved salts) directly by reverse osmosis, at a cost of about 10 per 1000 liters. 

As we have discussed already, the property of membrane semipermeability applies to all sorts of systems. Likewise, reverse osmosis may be applied to a wide variety of systems. An application that has attracted a great deal of interest in recent years is the production of potable water from saline water. Since no phase transitions are involved as, for example, in distillation, the method offers some prospect of economic feasibility in coastal regions. 

Legislation, environmental issues, customer demands, and economic reasons have increased interest in membranes. According to the Paperbase databank, in 1990 the word ultrafiltration was mentioned in more than 100 different papers and reverse osmosis in about 70 papers. In 2005, the corresponding numbers were 500 and 220. However, the seemingly intensive research has not yet created many mill-scale installations. 

---