Algae, Coagulation, and Ozonation
In addition to the direct disinfecting and oxidizing benefits of ozone, several secondary benefits have been attributed to its use. These include 1) microflocculation (i.e., the spontanaeous flocculation of particles), 2) a reduction in coagulant dosages, 3) improved water quality (usually measured as turbidity) following filtration through deep bed granular filters, and 4) a reduction in the filter bed head loss gradient. How ozone causes a reduction in the coagulant dose or induces flocculation is not well understood. Several proposed mechanisms are listed and discussed in a recently published book on ozone (Langlais, Reckhow, and Brink, 1991). These include: 1) increased Al complexation with natural organic matter (NOM), 2) increased Ca complexation with NOM, 3) reduction in particle stability due to loss of adsorbed organic matter from natural particles, 4) polymerization of NOM, 5) break-up of metal-organic complexes such as iron yielding in situ production of metal coagulant, and 6) reactions with algae.
KeywordsFiltration Ozone Phytoplankton Polysaccharide Shrinkage
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