Uses of Reverse Osmosis

Desalination of seawater and brackish water for potable use. This is very common in coastal areas and.the Middle East where supply of fresh water is scarce. 

Generation of process water for beverages (fruit juices, bottled water, beer). 

Waste treatment for the recovery of process materials such as metals for the metal finishing industries, and dyes used in the manufacture of textiles. 

Water reclamation of municipal and industrial waste-waters. 

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Memhra.nes. Liquid separation via membranes, ie, reverse osmosis (qv), is used in production of pure water from seawater. The chief limit to broader use of reverse osmosis is the high pressure required as the concentration of reject rises. 

The use of reverse osmosis (RO), electrodialysis reversal (EDR) and other membrane techniques, and evaporation or demineralization may be applicable when a reduction in the TDS content of the MU water source is required. 

This method is used mainly to remove high-molecular-weight materials such as proteins, colloids, viruses, and bacteria. The same types of problem encountered with the use of reverse osmosis membranes are encountered here, and the proposed solutions are the same. 

Although the USP allows generation of water for injections by use of reverse osmosis, this is not in line with the FDA opinion. Therefore, water for injections should always be generated by distillation. 

Use of reverse osmosis or HPLC grade water in every step requiring water is recommended. 

There are assessments predicting the use of reverse osmosis for the processing of the wastes from medical application [36,37] and for the removal of caesium-137 from decontamination wastes after accident in the steel production factory [38]. RO is considered as a method for removal of radioactive pollutants from contaminated water (removal of Cs and °Sr) in the vicinity of atomic power plants [39], as well as for removal of small quantities of radionuclides ( Rn, Ra) from... 

The USP 28 and the JP 2001 permit the use of reverse osmosis (RO) in addition to distillation and ultrafiltration. Purified water suitable for use in pharmaceutical formulations is usually prepared by purifying potable water by one of several... 

For dilute feeds, consider options for preconcentrating the feed to reduce the volumes of feed and solvent that must be handled by the extraction operation. Consider evaporation or distillation of a high-volatility feed solvent or the use of reverse osmosis membranes to concentrate aqueous feeds. (See Hybrid Extraction Processes under Commercial Process Schemes. )... 

However, with more stringent guidelines and since Whitestone was discharging Its waste after treatment directly to a stream, it was decided to install an RO system on the final aeration pond. A pilot test of approximately 1000 hours showed the usefulness of reverse osmosis and allowed Osmonics to specify the membrane elements and system layout with sufficient certainty to guarantee a reasonable life and operating characteristics to Whitestone. 

Reverse Osmosis Experiments. This work makes further use of reverse osmosis data already reported with respect to membranes made from cellulose acetate Eastman E-398 polymers ( >, 5, ). 

The use of reverse osmosis to treat dialysis water does not remove chloramine, but the addition of ascorbic acid does. Treating the dialysis water with activated charcoal effectively removes chloramine, but periodic water testing with o-tol-idine should nevertheless be undertaken. This reagent detects total chloride, i.e., OC1, HOC1, NHC12, and NC13. Interestingly, chloramine contamination of natural waters has also caused hemolysis in several species of freshwater fish (El). 

Recycling Sumitomo Chemical demonstrates a positive approach to recycling as a means of reducing environmental impact. In 1991 it set up a Committee for Plastics Recycling , which is working both to develop easy-to-recycle plastics, and to mould regenerated plastics. Examples of other initiatives include the recovery of sodium ion and sulphur from wastewater and the use of reverse osmosis for recovering caprolactam. 

Table 4.13 below shows the uses of reverse osmosis as described above. 

One of the most innovative industrial uses of reverse osmosis is at the Petromin Refinery in Riyadh, Saudi Arabia. The refinery takes an unusable municipal wastewater, secondary effluent from the Riyadh sewage treatment plant, and by using lime clarification, filtration, reverse osmosis and ion exchange demineralization, it converts that useless waste into the entire process water requirements for the refinery. Figure 4.16 is the process flow schematic for the refinery water treatment plant. 

An important factor to be remembered is that in some cases water supplies unsatisfactory for processing to high purity water may be the only sources available. Preliminary demineralization by reverse osmosis will make this water suitable for subsequent demineralization by ion exchange. It is thus apparent that such an economically important factor as plant site location, which may be dependent on the availability of suitable water, can be made more flexible through the use of reverse osmosis. It may be possible now to utilize seawater as a source of industrial process water. 

The nickel plating industry is a typical candidate for the use of reverse osmosis in pollution control. Figure 4.17 shows a schematic of this industrial application. The workpiece travels from the plating bath with a concentration of 270,000 mg/E to the rinse tanks. There are three rinse tanks in series and rinse water flows countercurrent to the workpiece. The work piece drags out plating bath to the first rinse tank, first rinse tank solution to the second rinse tank and second rinse tank solution to the third rinse tank. Consequently, the first, second and third rinse tanks have concentrations of 3,000 mg/E, 333 mg/E and 37 mg/) , respectively. 

Desalination of seawater and brackish water has been and, as of the end of the 1990s, is the primary use of reverse osmosis. Driven by a need for potable water in areas where there is a shortage, this industry has developed significantly. Desalination involves the reduction of the total dissolved solids (TDS) concentration, which is equal to more than 30,000 ppm, to less than 200 ppm. 

Parshall has described the use of reverse osmosis through a semipermeable membrane as an alternative method of separating product and reaction mixture. 

Tang CY, Fu QS et al (2006) Use of reverse osmosis membranes to remove perfluorooctane sulfonate (PFOS) from semiconductor wastewater. Environ Sci Technol 40(23) 7343-7349... 

There are restrictions for the use of reverse osmosis for effluent treatment. Nearly all the previous uses of reverse osmosis have been in metal recovery and recycling within the electroplating industry. The use of reverse osmosis for simple effluent treatment is rather restricted due to the chemical stability of the membrane. Often, industrial effluents are highly corrosive solutions containing hydroxide or acids. The membranes, which are essentially organic polymers, are quickly decomposed by hydroxide and acid. This can lead to rapid mechanical failure of the membrane especially under the high pressures used in reverse osmosis. Consequently the... 

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