No announcement yet.


  • Time
  • Show
Clear All
new posts

  • Ozonation

    Greetings All !

    In researching a response to a post in another thread, I stumbled across this little tidbit. If you're interested inthe process of ozonation is marine ecosystems, perhaps this will be of interest to you.


    In recent years, ozone is used more and more for disinfection of water. One of the reasons for this could be that ozone can nowadays be produced much more safely and economically photochemically (McGregor, 1986). The principles of the photochemical generation of ozone (using mercury lamps) have been clearly outlined by Dohan and Masschelein (1986).

    Ozone is mainly used for 2 purposes: disinfection and discolouration, but it can also have some effect in removing turbidity (Ramos and Ring, 1980). It has been claimed that ozone can reduce the TOC (total organic carbon) concentration in water by converting low molecular weight organic substances, such as methanol or ethanol to carbon dioxide (but also to acetic acid or aceton) (Elia et al, 1978). However, it doesn't have any effect on TOC levels in aquaria and marine mammal pools (Spotte (1979b), Adams and Spotte (1980)). When reacting with organic matter, ozone will first attack carbon double bonds (Kinne, 1976). It is probably this reaction that explains the ability of ozone of removing colour: pigments contain carbon double bonds and can also contain phenol rings (Spotte, 1979b). It means that ozone is active primarily against colour from organical sources.

    As a disinfectant it is more active against E. coli, but also against plankton, insect larvae and possibly viruses, than chlorine. Its disinfecting powers decrease at higher densities of organisms (Farooq et al, 1977) and at higher turbidities (Ramos and Ring, 1980).

    Its effect on turbidity can be explained by the conversion of POC (particulate organic carbon) into DOC (dissolved organic carbon). At higher DOC levels this conversion will not take place, because ozone will react with the DOC first (Spotte, 1979b). Ozonation of water containing dissolved organic matter can even increase turbidity. When ozone reacts with organic matter, polar, negatively charged groups (like carboxyl and hydroxyl groups) are formed. Complexing with polyvalent cations can then result in precipitation of the organic matter (microflocculation) (Rice, 1986). If turbidity increases or decreases following ozonation depends on the total composition of the water.

    In sea water the reactions of ozone are more complicated, because all kinds of side reactions can occur. It can for instance react with the trace metals Fe2+ and Mn2+ and oxidize them to Fe(OH)3 and MnO2 respectively, both of which can precipitate in this form and may be removed from the solution (Rice, 1986). It can also react with the chloride ion Cl- and convert that to hypochlorite ClO- (Keenan and Hegemann, 1978).

    Ozone does not leave any, possibly toxic, byproducts in the water and is therefore a convenient disinfectant for animal pools. On the other hand it doesn't leave a residual disinfecting agent either, so it doesn't have a long lasting effect. This makes the demands on the hydraulics of a water recirculation system higher.

    Extracted from:
    A biological approach to water purification: I. Theoretical aspects
    J.D. van der Toorn (1987)
    From: Aquatic Mammals 13(3): 83-92

    Anchored Table of Contents

    "When the going gets weird, the weird turn pro."
    Hunter S. Thompson