Water purification desalination

Because of its high salt content, seawater is unfit for human consumption and for most of the uses to which we put water. In the United States, the salt content of municipal water supplies is restricted by health codes to no more than about 0.05% by mass. This amount is much lower than the 3.5% dissolved salts present in seawater and the 0.5% or so present in brackish water found underground in some regions. The removal of salts from seawater or brackish water to make the water usable is called desalination. 

Water can be separated from dissolved salts by distillation because water is a volatile substance and the salts are nonvolatile, ogo (Section 1.3, Separation of Mixtures ) The principle of distillation is simple enough, but carrying out the process on a large scale presents many problems. As water is distilled from seawater, for example, the salts become more and more concentrated and eventually precipitate out. Distillation is also an energy-intensive process. 

What feature of this process is responsible for its being called reverse osmosis  

What is the primary function of the aeration step in water treatment  

Iodine-impregnated beads kill bacteria, viruses, and parasites 

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Water Purification Desalinization Chemicals Oilfield Chemicals Corrosion Inhibitors Biocides... 

Grimm J, Bessarabov D, and Sanderson R. Review of electro-assisted methods for water purification. Desalination 1998 115(Suppl. 8) 285-294. 

In conclusion, biomaterial CS, which is the second highest naturally occurring polymer, can be modified easily by chemical methods. So modified CS derivatives or CS is finding vast applications in the field of water purification (desalination, dye and heavy metal removal, etc.), fuel cell application, pervaporation, and hemodialysis. There is a large scope to implement this polymer in its various novel chemically modified forms, in order to exploit further applications in the membrane field. 

Macedonio F, Drioli E. (2008), Pressure-driven membrane operations and membrane distillation technology integration for water purification. Desalination, 223,396-409. 

Macedonio, E, E. Drioli, Pressure-Driven Membrane Operations and Membrane Distillation Technology Integration for Water Purification. Desalination, 2008, 223(1), 396 09. 

Membranes can be defined as selective barriers between two phases and have a plethora of apphcations, including water purification, desalination, drug development, and chemical sensing. BCP SA can be a useful approach for membrane fabrication because tunable structure and narrow size control of membrane pores is possible. 

Mo, L., and Huanga, X. (2003). Fouling characteristics and cleaning strategies in a coagulation-microfiltration combination process for water purification. Desalination 159, 1-9. 

Among electrochemical methods of water purification, one can also list the various electromembrane technologies, electrodialysis in particular. The simplest elec-trodialyzer consists of three compartments separated by semipermeable membranes (usually, cation- and anion-exchange membranes). The water to be purified is supplied to the central (desalination) compartment. In the outer (concentration) compartments, electrodes are set up between which a certain potential difference is applied. Under the effect of the electric field, ions pass througfi the membranes so that the concentration of ionic contaminants in the central compartment decreases. 

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). 

Ahmed, M., Shayya, W.H., Hoey, D., Mahendran, A., Morris, R., Al-Handaly, J. Use of evaporation ponds for brine disposal in desalination plants. Desalination 130(2), 155-168 (2000) Mickley, M. Treatment of Concentrate, Desalination and Water Purification Research and Development Program Report No. 155. U.S. Department of the Interior, Bureau of Reclamation, Denver (2009)... 

Mickley, M. Treatment of Concentrate, Desalination and Water Purification Research and Development Program Report No. 155. U.S. Department of the Interior, Bureau of Reclamation, Denver (2009)... 

Refs. [i] Spiegler KS (1980) Salt water purification, 2nd edn. McGraw-Hill, New York [ii] Korngold E, Kock K, Strathmann H (1978) Desalination 24 129 [Hi] McRae WA (1983) Electrodialysis. In Porteous A (ed) Desalination technology developments and practice. Applied Science, London, pp 249-264 [iv] Strathmann H (2002) Membranes and membrane separation processes. In Ullmanns encyclopedia of industrial chemistry, 6th edn. Wiley-VCH [v] Levy J, Morgan J, Brown E (2004) Oxford handbook of dialysis. Oxford University Press... 

In recent years, two other important applications of synthetic polymeric membranes in water purification have become establMied. Chronologically the first of these, reverse osmosis, is rapidly becoming the principal method of water desalination worldwide. Another membrane process, ultrafiltration, is even newer and is finding important use in the renurval of h molecular wei t, colloidal, and emulsified materials from aqueous streams. 

Membrane technology will play a major role in water treatment and wastewater reclamation, as indicated in Desalination and Water Purification Technology Roadmapp and will require continued research and development in ... 

U.S. Bureau of Reclamation Sandia National Laboratories. Desalination and Water Purification Technology Roadmap—A Report of the Executive Committee, Desalination Water Purification Research Development Program Report 95 2003. 

Neutralization dialysis is proposed to be suitable for water purification because weak acids (such as acetic acid, carbonate, bicarbonate ions), and weak bases (like amines, ammonia) easily permeate through the membranes.188 190 Soluble silicate compounds in water can be removed by this method. Also, desalination of protein solutions containing sodium chloride has been reported by using a spiral module, in which a cation exchange membrane, spacer and anion exchange membrane were wound alternately.191... 

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