Reverse osmosis Desalination

Evangelista, F. (1986). Improved graphical analytical method for the design of reverse osmosis desalination plants. Ind. Eng. Chem. Process Des. Dev., 25(2), 366-375. 

Boca Raton reverse osmosis desalination system, 26 82... 

Seawater reverse osmosis, 26 97 Seawater reverse osmosis desalination systems, 26 80... 

NF has been also been studied as a potential form of pretreatment for reverse osmosis desalination processes (Hassan et al. 1998, 2000). Based on the feed water, it may be a suitable pretreatment method that allows for operation with little or even no use of antisealants. 

Fritzmann, C., Lowenberg, J., Wintgens, T., Melin, T. State-of-the-art of reverse osmosis desalination. Desalination 216(1-3), 1-76 (2007). 

Co-location of a power plant and a seawater reverse osmosis desalination plant allows for the cooling water from a neighbouring power plant to be blended with the waste from a desalination plant before discharge (Voutchkov 2004). In such a process, seawater is used as the cooling water for the condensers in a power plant. This water is then used as both the feed for the desahnation process, and for blending to dilute the concentrate from the desalination plant. 

Figure 16. Decrease of separation (or increase of solute permeabilities) of seawater reverse osmosis desalination at several concentration levels of NaOCl. Initial membrane constants pure water permeability constant = 97.0 nmol m Pa s and the solute permeability constant for NaCl = 0.9 X 10 cm s . Operational conditions k = 7.(97 X 10 cm s Ap = 6.0 MPa, and T = 25°C.

Reverse osmosis desalination plants consisting of 8 long tubular membranes prepared from commercial CA of D.S. 2.5 were set up for supply of drinking water and boiler feed water at two different locations. 

It is the rate of separation rather than the efficiency of salt retention that is the primary practical issue in the development of reverse osmosis desalination. In addition to a variety of other factors, the rate of reverse osmotic flow depends on the excess pressure across the membrane. Therefore the problem of rapid flow is tied into the technology of developing membranes capable of withstanding high pressures. The osmotic pressure of sea water at 25 °C is about 25 atm. This means that no reverse osmosis will occur until the applied pressure exceeds this value. This corresponds to a water column about 840-ft high at this temperature. 

The greatest use of membranes is for reverse osmosis desalination of seawater and purification of brackish waters. Spiral wound and hollow fiber equipment primarily are applied to this service. Table 19.6 has some operating data, but the literature is very extensive and reference should be made there for details of performance and economics. 

Strathmann et al.20) examined the water and salt sorption and the homogeneity of water distribution in various polymers and indicated that the uniformity of water distribution in the polymer is an important parameter controlling reverse osmosis desalination efficiency. As summarized in Table 2, the average number of water molecules included in a cluster is 1.4 to 2.9 for the superior barrier materials such as aromatic polyamides, polyamide-hydrazide, and polybenzimidazopyrrolone, while the number for the other polymer membranes is larger than 5. 

Figure 4.4 Salt concentration gradients adjacent to a reverse osmosis desalination membrane. The mass balance equation for solute flux across the boundary layer is the basis of the film model description of concentration polarization...

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). 

Electrical power is the energy source for RO desalination. A reverse-osmosis desalination plant is presented schematically in Figure 10.3. Electricity is used to... 

Figure 10.3 Schematic presentation of a reverse-osmosis desalination plant.

Although the integration of RO with other pressure-driven membrane processes has led to significant improvements in membrane-based desalination process economics, another fundamental problem is the environmental aspects of brine discharge from reverse-osmosis desalination plants. 

Various process engineering strategies have been investigated in order to have a more environmentally friendly strategy for brine disposal in reverse-osmosis desalination. 

A small-scale, manually operated reverse osmosis desalinator has been developed by the U.S. Navy to provide fresh water on life rafts (Fig. 1 ,19). Potable water can be supplied by this desalinator at the rate of 1.25 gallons of water per hour—enough to keep 25 people alive. This compact desalinator, which weighs only 10 pounds, replaces the bulky cases of fresh water formerly stored on Navy life rafts. 

Alawadhi, A. A. (1997). Pretreatment plant design—Key to a successful reverse osmosis desalination plant, Desalination Int. Symp. Pretreatment of Eeedwater for Reverse Osmosis Desalination Plants, March 31-April 2, 110, 1-2, 1-10. Elsevier Science B.V., Amsterdam, Netherlands. 

Kiranoudis, C. T., N. G. Voros, and Z. B. Maroulis (1997). Wind energy exploitation for reverse osmosis desalination plants. Desalination. 109, 2, 195-209. 

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