Use of DAF for Seawater Pretreatment

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Use of DAF for Seawater Pretreatment – do you think that dissolved air flotation is an effective technology for removal of algae from seawater?  Are you aware of successful DAF applications?

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  1. DAF for Seawater Pretreatment

     

    Hi Sara:

    I think that the DAF, if designed appropriately, is technology which can successfuly remove the majority of algae in seawater (over 85 to 90 %). The main problem with most exisitng DAF installations for seawater pretreatment is that they use DAF technologies designed for removal of fresh water algae inhabiting lakes, rivers and other surface water bodies. Use of fresh water or wastewater DAF technologies for seawater pretreamtent does not work well mainly because the size of seawater algae is an order of magnitude smaller that that of fresh water algae, and becasue seawater is heavier than fresh water and requires different design of the air saturation system and the air nozzles. In additon, the charge of seawater and fresh water algae is different and this difference requires differrnt design of the coagulation and flocculation chambers upstream of the DAF units.

    The use of DAF for seawater pretreatment so far has been very limited and in most applications - unsuccessful for the reasons manioned above. In my oppinion, the DAF technology providers will have to develop a new generation of DAF systems tailored to address the specific differences of seawater and seawater algae and water quality. Once that happnes I do believe that DAF will become suitable for seawater pretreatment.

    If you are planning to attend the IWA conference in Busan, Korea next week, we could discuss this topic in greater detail in person.

    Nikolay Voutchkov
    Water Globe Consulting
    nvoutchkov@water-g.com