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This paper examines significant developments in dissolved air flotation (DAF) that have occurredover the last 40 years. DAF processes are being designed and operated with shorter flocculationdetention times than have been used in the past. Fundamental concepts show that flocs of 20-50m are optimum in size regarding the collisions and attachment of flocs to air bubbles in theDAF contact zone, and thus link flocculation practice to fundamentals. Floc-bubble aggregatescan rise and be removed in the DAF separation zone with one bubble attachment to flocs withsizes 50 m. Data are presented showing the effectiveness of DAF for treating low turbiditywaters containing total organic carbon (TOC) and for removing algae and Cryptosporidium oocysts. High rate DAFsystems are a recent development (over the last 10 years) with hydraulic loadings of 8-16 gpm/sf thatyield a small process footprint. These high rate processes have different hydraulic flow throughpatterns than conventional rate DAF that allow them to produce high quality clarified water. Includes 15 references, figures.

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Edition: Vol. - No. Published: 11/01/2008 Number of Pages: 11File Size: 1 file , 820 KB