Water and Wastewater Terms Beginning S

A B C D E F G H I J K L M N O P Q R S T U V W Y Z

sludge volume index (SVI)

A calculation that indicates the tendency of activated sludge solids (aerated solids) to thicken or to become concentrated during the sedimentation/thickening process. SVI is calculated in the following manner:

1. allow a mixed liquor sample from the aeration basin to settle for 30 minutes;
2. determine the suspended solids concentration for a sample of the same mixed liquor;
3. calculate SVI by dividing the measured (or observed) wet volume (mL/L) of the settled sludge by the dry weight concentration of MLSS in grams/L.