Brackish and seawater desalination

Albany International Research Co. has developed an advanced hollow fiber composite reverse osmosis membrane and module under the name of Quantro II . This composite membrane is comprised of a porous hollow fiber substrate on which has been deposited a rejection barrier capable of fluxes of commercial importance at high rejection of dissolved salts at elevated temperatures. Resistance to active chlorine has been demonstrated. Proprietary processes have been developed for spinning of the fiber, establishment of the rejection barrier and processing of the fiber to prepare modules of commercial size. Prototype modules are currently in field trials against brackish and seawater feed solutions. Applications under consideration for this membrane include brackish and seawater desalination as well as selected industrial concentration processes. 

R.L. Riley, C.E. Milstead, A.L. Lloyd, M.W. Seroy and M. Takami, Spiral-wound Thin Film Composite Membrane Systems for Brackish and Seawater Desalination by Reverse Osmosis, Desalination 23, 331 (1977). 

The reverse-osmosis membrane process is considered universally as the most promising technology for brackish and seawater desalination [18]. Potential directions for reducing desalination costs may be deduced by analyzing the cost of the components. 

Integration of brackish and seawater desalination systems. In many places brackish water can be found close to the sea. Integrating the two types of desalination may reduce the cost of the final product. 

Membrane research and development started in Du Pont in 1962 and culminated in the introduction of the first B-9 Permasep permeator for desalination of brackish water by reverse osmosis (RO) in 1969. The membrane in this B-9 Permasep module consisted of aramid hollow fibers. In 1969, proponents of RO technology had ambitious dreams and hopes. Today, RO is a major desalination process used worldwide to provide potable water from brackish and seawater feeds. Du Font s membrane modules for RO are sold under the trademark Permasep permeators. The RO business is a virtually autonomous profit center that resides in the Polymer Products Department. The growth and success of the Permasep products business is a direct result of Du Font s sustained research and development commitment to polyamides, a commitment that dates back to the 1930 s and the classic polymer researches of Wallace H. Carothers. Since 1969, improved and new Permasep permeators have been introduced six times, as shown in Table I. 

Gugliuzza A., Speranza V., Macedonio E, Drioli E. (2010), High-performance hydrophobic membranes for contactors and desalination technologies, Proc. of Advances in Science and Engineering for Brackish Water and Seawater Desalination (ECI), May 8-12, Cetraro, Italy, 122-124... 

Frenkel V (2008), Brackish vs Seawater Desalination Which one is for you . International Desalination and Water Reuse Quarterly, 17,47-50. 

Reverse osmosis processes for desalination were first appHed to brackish water, which has a lower I DS concentration than seawater. Brackish water has less than 10,000 mg/L IDS seawater contains greater than 30,000 mg/L IDS. This difference in IDS translates into a substantial difference in osmotic pressure and thus the RO operating pressure required to achieve separation. The need to process feed streams containing larger amounts of dissolved soHds led to the development of RO membranes capable of operating at pressures approaching 10.3 MFa (1500 psi). Desalination plants around the world process both brackish water and seawater (15). 

The pressure to be used for reverse osmosis depends on the salinity of the feedwater, the type of membrane, and the desired product purity. It ranges from about 1.5 MPa for low feed concentrations or high flux membranes, through 2.5—4 MPa for brackish waters, and to 6—8.4 MPa for seawater desalination. In desalination of brackish or sea water, typical product water fluxes through spiral-wound membranes are about 600—800 kg/m /d at a recovery ratio RR of 15% and an average salt rejection of 99.5%, where... 

Applications RO is primarily used for water purification seawater desalination (35,000 to 50,000 mg/L salt, 5.6 to 10.5 MPa operation), brackish water treatment (5000 to 10,000 mg/L, 1.4 to 4.2 MPa operation), and low-pressure RO (LPRO) (500 mg/L, 0.3 to 1.4 MPa operation). A list of U.S. plants can be found at www2.hawaii.edu, and a 26 Ggal/yr desalination plant is under construction in Ashkelon, Israel. Purified water product is recovered as permeate while the concentrated retentate is discarded as waste. Drinking water specifications of total dissolved solids (TDS) < 500 mg/L are published by the U.S. EPA and of < 1500 mg/L by the WHO [Williams et ak, chap. 24 in Membrane Handbook, Ho and Sirkar (eds.). Van Nostrand, New York, 1992]. Application of RO to drinking water is summarized in Eisenberg and Middlebrooks (Reverse Osmosis Treatment of Drinking Water, Butterworth, Boston, 1986). 

Reverse osmosis membrane process, 27 637 Reverse osmosis membrane cleaning citric acid application, 6 647 Reverse-osmosis membranes, 75 811, 825 development of, 75 797 Reverse osmosis models, 27 638-639 Reverse osmosis permeators, 76 19 Reverse osmosis seawater desalination process, 26 85 Reverse osmosis systems blending in, 26 80-81 brackish and nanofiltration, 26 80-83 Reverse osmosis technology... 

The concentrations of seawater and brackish water can vary significantly, and as such there is a difference between the concentrate produced from seawater desalination plants and brackish water desahnation plants. Seawater typically has a level of total dissolved solids (TDS) between 33,000-37,000 mg/L. The average major ion concentration of seawater is shown in Table 2.1 along with water from the Mediterranean Sea, and water from Wonthaggi off the southern coast of Australia. Seawater sahnity increases in areas where water evaporates or freezes, and it decreases due to rain, river runoff, and melting ice. The areas of greatest salinity occur and latitudes of 30° N and S where there are high evaporation rates. 

Approximately one-half of the reverse osmosis systems currently installed are desalinating brackish or seawater. Another 40 % are producing ultrapure water for the electronics, pharmaceutical, and power generation industries. The remainder are used in small niche applications such as pollution control and food processing. A review of reverse osmosis applications has been done by Williams et al. [52],... 

Brackish waters contain between 0.05 and 1 wt % TDS. Their lower osmotic pressures allow reverse osmosis operation between 15 and 30 bar. Less expensive pressure equipment and energy consumption translate to more favorable water production economics than those for seawater desalination. 

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