Market reverse osmosis

Although these composite fibers were developed for reverse osmosis their acceptance in the desalination industry has been limited due to insufficient selectivity and oxidative stabiUty. The concept, however, is extremely viable composite membrane fiat films made from interfacial polymerisation (20) have gained wide industry approval. HoUow fibers using this technique to give equivalent properties and life, yet to be developed, should be market tested during the 1990s. 

Reverse Osmosis. This was the first membrane-based separation process to be commercialized on a significant scale. The breakthrough discovery that made reverse osmosis (qv) possible was the development of the Loeb-Sourirajan asymmetric cellulose acetate membrane. This membrane made desalination by reverse osmosis practical within a few years commercial plants were installed. The total worldwide market for reverse osmosis membrane modules is about 200 million /yr, spHt approximately between 25% hoUow-ftber and 75% spiral-wound modules. The general trend of the industry is toward spiral-wound modules for this appHcation, and the market share of the hoUow-ftber products is gradually falling (72). 

Although the principal appHcation of reverse osmosis membranes is still desalination of brackish water or seawater to provide drinking water, a significant market is production of ultrapure water. Such water is used in steam boilers or in the electronics industry, where huge amounts of extremely pure water with a total salt concentration significantly below 1 ppm are required to wash siUcon wafers. 

Desalinated seawater and desalinated brackish water are important new sources of fresh water. Although this fresh water is more costly than fresh water from natural sources, one could argue that the higher cost reflects fresh water s true value. In the United States, natural sources of fresh water are relatively plentiful, allowing companies to sell fresh water at rates of a fraction of a penny per liter. Nonetheless, consumers are still willing to buy bottled water at up to 2 per liter Each year Americans spend about 400 million dollars on bottled water, and the market continues to grow rapidly. Unless we conserve fresh water, it is easy to project a growing reliance on distillation and reverse osmosis. 

The four developed industrial membrane separation processes are microfiltration, ultrafiltration, reverse osmosis, and electrodialysis. These processes are all well established, and the market is served by a number of experienced companies. 

Currently, approximately one billion gal/day of water are desalted by reverse osmosis. Half of this capacity is installed in the United States, Europe, and Japan, principally to produce ultrapure industrial water. The remainder is installed in the Middle East and other desert regions to produce municipal drinking water from brackish groundwater or seawater. In recent years, the interfacial composite membrane has displaced the anisotropic cellulose acetate membrane in most applications. Interfacial composite membranes are supplied in spiral-wound module form the market share of hollow fiber membranes is now less than... 

Cellulose acetate was the first high-performance reverse osmosis membrane material discovered. The flux and rejection of cellulose acetate membranes have now been surpassed by interfacial composite membranes. However, cellulose acetate membranes still maintain a small fraction of the market because they are easy to make, mechanically tough, and resistant to degradation by chlorine and other oxidants, a problem with interfacial composite membranes. Cellulose acetate membranes can tolerate up to 1 ppm chlorine, so chlorination can be used to sterilize the feed water, a major advantage with feed streams having significant bacterial loading. 

The current ultrafiltration market is approximately US 200 million/year but because the market is very fragmented, no individual segment is more than about US 10-30 million/year. Also, each of the diverse applications uses membranes, modules, and system designs tailored to the particular industry served. The result is little product standardization, many custom-built systems, and high costs compared to reverse osmosis. The first large successful application was the recovery... 

Electrodialysis is now a mature technology, with Ionics remaining the worldwide industry leader except in Japan. Desalting of brackish water and the production of boiler feed water and industrial process water were the main applications until the 1990s, but electrodialysis has since lost market share due to stiff competition from improved reverse osmosis membranes. Beginning in the 1990s,... 

In some regions of the southwest United States, the water is very hard. For example, in Las Cruces, New Mexico, the tap water contains about 560 /xg of dissolved solids per milliliter. Reverse osmosis units are marketed in this area to soften water. A typical unit exerts a pressure of 8.0 atm and can produce 45 L of water per day. 

As pressure on existing freshwater supplies tightens, seawater desalination plants, using multieffect vacuum distillation or reverse osmosis, are required in increasing numbers for provision of freshwater. The residual evaporated brines from these plants contain much higher salt concentrations than ordinary seawater and this is also obtained near potential salt markets. 

Membrane processes are one of the most important separation technologies in food industry. The operate, at room temperature, require no addition of chemicals and are gentle and non-destruc ive. Their potentiality is confirmed by an annual growth rate of 37% (1). However the major area for ultrafiltration and reverse osmosis in food applications is mainly whey purification, and the dairy industry in general. This market has been estimated of 2 million US dollars in 1976 and 5 million US dollars in 1981. 

Since the first cellulose-acetate membrane was made, and the hollow fine fiber was introduced, very few new membranes for reverse osmosis have been brought on the market. 

We believe that for reverse osmosis new membranes with high chemical stability, high temperature resistance, and improved performance rates in respect to rejection characteristics and flux rates are coming on the market very soon in the form of improved thin-film composite membranes. 

Whether we cail the process we have talked about during this week reverse osmosis or hyperfiltration or ultrafiltration is of little importance. The important thing is that the membrane invented by Loeb and Sourirajan slightly over 20 years ago is a marketable product and has a fantastic future. Too often we allow semantics to act as a barrier to our mutual understanding of this technology. 

During the 1960 s, the DuPont Company screened numerous polymers to determine the suitability of materials other than cellulose acetate for use in reverse osmosis desalination. The results of this work indicated that aromatic polyamides were the "choice as the best polymer type for use in the DuPont commercial permeators".7 The company was most successful in developing an asymmetric aromatic polyamide reverse osmosis membrane in a hollow fine fiber configuration which successfully competed with cellulose acetate in the market place. 

The initial projections of 20 years ago have proven to be unrealistic in that reverse osmosis has not caused deserts to bloom, nor does every household contain a reverse osmosis unit to improve the tap water. Yet, the process has been of economic value in providing process water to industry, potable water to high income arid regions and a method of reclaiming municipal and industrial wastes. As of 1985, it was estimated that the worldwide market for reverse osmosis membrane elements (not total systems) was about 50 million. 

Finally, as the world becomes more aware of the environmental damage caused by indiscriminate waste disposal it is apparent the RO process will play a key role in mitigating that problem. It appears that the next market for the RO process will be in industrial waste treatment in the United States to be followed by application in other countries. Eventually, the world will be forced to use reverse osmosis to reclaim municipal wastewater on a large scale and to put the reclaimed water to a number of already demonstrated beneficial uses. 

Major growth predicted in reverse osmosis market by 2012... 

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