Electrochemistry in water and effluent treatment

Electrochemistry can be used for a number of purposes linked to water and effluent treatment. The most obvious of these involve the removal of ionic components from waters by application of an appropriate potential. This is employed to remove metal ions from process streams and often leads to recovery of the metal, which can be reused. Clearly, cell designs which favour high electrode surface area/catholyte volume ratios are to be recommended. 

Cleaning of organic contamination in effluents and in sewage can be aided by electrochemistry in the following ways  

Ionic species in waters can be concentrated, and the water purified at the same time, by electrodialysis. Ion-exchange membranes are employed with an applied electric field in order to force ionic salts to pass from dilute into concentrated solutions. Examples of the use of electrodialysis are in the concentrating of Ni2+ in used nickel plating solutions for recirculation, and in desalination plants in the purification of sea water or well water to acceptable levels to make it fit for drinking. 

Pletcher and F. C. Walsh, Industrial electrochemistry, 2nd edn., Chapman and Hall, London, 1990. 

Heitz and G. Kreysa, Principles of electrochemical engineeringy VCH, Weinheim, 1986. 

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For a detailed discussion the reader is referred to a number of recent monographs [9,10,23] and review articles [50,226-231]. The role of electrochemistry in waste water and effluent treatment is still queried, as remarked by Pletcher and Walsh [10]. One answer would be, relatively small since there are many competitive methods which are cheaper on a large scale and use less energy. Principle types of processes used in local-authority sewage works are listed in Table 14. 

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