Regulating Plant Disinfection in Seawater Desalination

  • ChemPubSoc Europe Logo
  • Author: Cordula Buse
  • Published Date: 10 November 2019
  • Source / Publisher: Chemie Ingenieur Technik/Wiley-VCH
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
thumbnail image: Regulating Plant Disinfection in Seawater Desalination

Reverse osmosis membranes in seawater desalination plants are prone to deposits building during operation, also known as biofouling. To prevent the resulting increased energy requirements, higher costs, and shorter equipment lifespan, the membrane is disinfected with chlorine components such as Cl2 gas or hypochloric acid. Because the chlorine residues after disinfection lead to irreparable oxidation damage to the membrane, they are removed by adding a reducing agent such as sodium metabisulfite (Na2S2O5). In aqueous environments, it dissociates into sulfite (SO32–) and bisulfite (HSO3–), which reduce the free chlorine to chloride. This eliminates the oxidative risk to the membrane. Since no in situ monitoring of the complete reducing reaction is available, the Na2S2O5 is overdosed stoichiometrically to protect the membranes.

Jan Birkmann and colleagues from the University Duisburg-Essen, Germany, propose a combination of UV spectroscopy and regression analysis to determine the concentration of sulfur species in situ. This information can be used to calculate the progress of the chlorine reduction and optimize the addition of the reducing agent. A first model was developed by measuring the sulfur(IV) spectroscopically in ultrapure water and using the spectra for a PLS (partial least squares) regression analysis. The model was then extended to a more complex system of artificial seawater to study the influences of other components. While sulfur can always be detected qualitatively, independent of the pH caused by the chlorine used in the disinfection process, a quantitative assessment is only possible at high sulfur concentrations.

Deeper analysis revealed that sulfite concentrations could be determined with good quality, whereas bisulfite detection was not reliable due to interferences with other seawater components. Therefore, to apply this method in real seawater desalination plants, further improvements to the analytical quality are needed.


 

 

 

Article Views: 424

Sign in Area

Please sign in below

Additional Sign In options

Please note that to comment on an article you must be registered and logged in.
Registration is for free, you may already be registered to receive, e.g., the newsletter. When you register on this website, please ensure you view our terms and conditions. All comments are subject to moderation.

Article Comments - To add a comment please sign in

Bookmark and Share

If you would like to reuse any content, in print or online, from ChemistryViews.org, please contact us first for permission. more


CONNECT:

ChemistryViews.org on Facebook

ChemistryViews.org on Twitter ChemistryViews.org on YouTube ChemistryViews.org on LinkedIn Sign up for our free newsletter


A product of ChemPubSoc Europe (16 European Chemical Societies)and Wiley-VCH