Conventional and AWT Mixed-Liquor Settling Characteristics

Settling characteristics of mixed liquor from seven advanced wastewater treatment (AWT) and two conventional wastewater treatment facilities in the Tampa Bay Metropolitan Area were evaluated. An algorithm was developed that relates zone settling velocity (Vs) of the mixed liquor to initial mixed-liquor suspended solids (MLSS) concentration and unstirred sludge volume index (uSVI) of the mixed liquor. Twotailed, paired comparison, Studentʹs t-tests indicated there was no significant difference between the sludge volume index (SVI) as measured in a 1 L unstirred graduated cylinder and that measured in a stirred, 28 L Plexiglas column. A secondary clarifier operating diagram is presented that can be used by engineers and operators in the design and operation of secondary clarifiers. Bye and Doldʹs model could be used to predict the SVIs of the mixed liquors evaluated in this study.