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In a recent pilot study conducted at Metropolitan King County's West Point WWTP, the ballasted flocculation processes (Actiflo and Densadeg 4D) were determined to out-perform conventional primary treatment with regard to average removal efficiencies and performance variability. A compressible media filter (Fuzzy Filter) technology was also tested.

The Actiflo process consistently achieved excellent TSS removal of 93 and 94 percent throughout the pilot testing. Turbidity removal averages 97 percent for three coagulants tested. BOD removal in the Actiflo ranged from 74 to 78 percent, and COD removal efficiency between 67 and 71 percent. PACl and ferric chloride achieved 92 and 91 percent phosphorus removal.

The Densadeg 4D process also achieved TSS removal of 85 percent to 96 percent and turbidity removal of 89 percent. COD removal efficiency was between 58 percent and 71 percent. Ferric chloride and alum achieved 85 percent and 91 percent phosphorus removal.

The Fuzzy Filter does not appear to be suitable for use in a primary treatment application under the conditions in this pilot study. Using the Fuzzy Filter to treat primary influent has not been tested before. Breakthrough of solids was observed within a short period of operation due to solids clogging at the bottom of the media and consequently causing short-circuiting of solids along the sidewall of the filter.

Document Type: Research Article


Publication date: 2002-01-01

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