Environmental Engineering LaboratoryBy: Ngoc Thuan Le

Sludge volume index (SVI)

Sludge volume index (SVI) is the volume of milliliters occupied by 1 gram of a suspension after 30

mins settling. SVI typically is used to monitor settling characteristics of activated sludge and other

biological suspension. Although SVI is not supported theoretically, experience has shown it to be

useful in routine process control.

Apparatus: Incubator, Spectrophotometer

Procedure:

1. Determine the suspended solids concentration of a well-mixed sample of the suspension.

2. Determine the 30 min settled sludge volume.

Calculation:

* SVI > 150 are typically associated with filamentous growth (Parker et al., 2001)

Precision and Bias:

- Precision is determined by the precision achieved in the suspended solids measurement, the

settling characteristics of the suspension, and variables associated with the measurement of

the settled sludge volume. Bias is not applicable.

Reference:

1. Standard methods for the examination of water and wastewater. 18th edition 1992 (APHA, AWWA,

WEF)