The parameter at a glance.
SVI combines the MLSS concentration with the volume occupied by sludge after settlement. It provides a repeatable way to compare activated-sludge settleability.
mL/g
Unit or result
30 minutes
Test timing
Calculated from the same sample
S3A scope
Understanding Sludge Volume Index (SVI).
SVI combines the MLSS concentration with the volume occupied by sludge after settlement. It provides a repeatable way to compare activated-sludge settleability. If a result rises unexpectedly, read what a high SVI can indicate before reviewing it with wider process evidence.
A combined result
SVI considers both solids concentration and settled sludge volume, so it should be reviewed with the associated MLSS and SSL results.
Follow site trends
Changes from the treatment works’ established SVI trend can indicate that settlement behaviour is changing and warrants review.
Process context matters
SVI is an operational indicator. It does not identify the underlying cause of a process change by itself.
One sample. A complete settlement picture.
The S3A measures MLSS rapidly, then continues the unattended 30-minute settlement test for SVI, SSL, supernatant clarity and floating sludge. The optional stirrer is required for SSVI and SSSL.
01 / MLSS
Rapid MLSS measurement
A result in approximately 10 seconds from a compact 210 ml sample, within the specified 50 to 6,500 mg/L range.
02 / Settlement test
Unattended settlement analysis
The analyser continues the 30-minute cycle and stores the completed result after the test has finished.
Designed for routine activated-sludge checks.
The S3A uses a compact 210 ml representative sample in a safe-area wastewater-treatment environment. The 30-minute settlement cycle runs unattended, allowing the operator to continue with other work.
Completed results can be stored for each of three locations, with date and time information.
Explore related S3A parameters.
See how the S3A measurements work together within one repeatable settlement-analysis workflow.
MLSS
Measure mixed liquor suspended solids from a compact 210 ml sample in approximately 10 seconds.
SSL
Record the volume occupied by activated sludge after the 30-minute settlement cycle.
Supernatant Clarity
Assess the solids remaining above the settled sludge after the settlement cycle.