Desalination reverse electrodialysis

Ion exchange desalination - DESAL , SIROTHERM Membrane desalination - Reverse Osmosis, Electrodialysis Continuing fixed bed counterflow development Condensate polishing systems Ion Chromatography analysis, and Pellicular resins Polymeric adsorbents... 

A new application area for membranes is energy production. Reverse electrodialysis and pressure retarded osmosis could provide significant quantities of energy from the mixing of fresh water with seawater or mixing the concentrated brine effluent of desalination plants with seawater. However, these applications will require significant reduction in membrane and module costs. 

Allison RP (1991) Surface and waste-water desalination by electrodialysis reversal, Proceedings, American Water Works Association Conference, Orlando, FL. 

Water desalination by the reverse electrodialysis process is less commonly employed than reverse osmosis. It typically uses two types of ion exchange membrane, one allowing only the passage of negatively charged ions (anions), and the other only allows the passage of positive ions (cations). Electrodialysis was (and is) a laboratory process, used to remove salts from certain colloidal solutions, but the development of membranes with selective permeability in relation to anions and cations has totally reactivated the process. 

TDS affects taste also, and waters over 500 - 600 ppm can taste poor. When the levels top 1500 ppm, most people will report the water tastes very similar to weak alka-seltzer. TDS is removed by distillation, reverse-osmosis or electrodialysis. In our area, most desalination projects, both large and small are accomplished with reverse-osmosis. Depending on the water chemistry, reverse osmosis systems are the most popular, given their low cost and ease of use. Distillers work very well also, and produce very high quality water, but require electricity and higher... 

Desalination using ion-exchange, electrodialysis, or reverse osmosis... 

All commercial types of processes, with the exception of freezing, namely, distillation, reverse osmosis and electrodialysis, are being applied in the above units with various kinds of distillation processes being used for seawater desalting. Two of them, horizontal tube multieffect distillation and vapor compression units were developed and manufactured locally by the Israel Desalination Engineering Ltd. Recently, two small RO units with a combined capacity of approx. 100 cu. m/day were also used to desalt seawater. The main aim of these units is to test and demonstrate the feasibility of this new technology. 

Cros, S., Lignot, B., Razafintsalama, C., Jaouen, P., and Bourseau, P. 2004. Electrodialysis desalination and reverse osmosis concentration of an industrial mussel cooking juice Process impact on pollution reduction and on aroma quality. J. Food Sci. 69, C435-C442. 

The traditional membrane separation processes (reverse osmosis, micro-, ultra- and nanofiltration, electrodialysis, perva-poration, etc.), already largely used in many different applications, are today combined with new membrane systems such as CMRs and membrane contactors. Membranes are applied not only in traditional separation processes such as seawater desalination but also in medicine, bioengineering, microelectronics, the life in the space, etc. 

Desalination of seawater is one of the important applications of membrane processes. There are various ways to produce fresh water such as distillation, electrodialysis, membrane distillation, freezing, membrane bioreactor, and reverse osmosis. Among them, distillation is the most used technique, but RO is becoming more popular in the desalination industry. A flow diagram of a single-stage RO system is shown in Fig. 4. 

FIGURE 5.4 Principles of operation of two types of membrane water desalination units reverse osmosis and electrodialysis. (From Pryde [22], and reprinted courtesy of Cummings Publishing Co.)... 

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