Conventional and AWT mixed-liquor settling characteristics

Settling characteristics of mixed Liquor from seven advanced wastewater tre atment (AWT) and two conventional wastewater treatment facilities in the Ta mpa Bay Metropolitan Area were evaluated. An algorithm was developed that r elates zone settling velocity (V-s) of the mixed liquor to initial mixed-li quor suspended solids (MLSS) concentration and unstirred sludge volume inde x (uSVI) of the mixed liquor. Two-tailed, paired comparison, Student's t-te sts indicated there was no significant difference between the sludge volume index (SVI) as measured in a 1 L unstirred graduated cylinder and that mea sured in a stirred, 28 L Plexiglas column. A secondary clarifier operating diagram is presented that can be used by engineers and operators in the des ign and operation of secondary clarifiers. Bye and Dold's model could be us ed to predict the SVIs of the mixed liquors evaluated in this study.