Sludge Volume Index (SVI)

Protocol 1.

Wash and dry at least 2 graduated measuring cylinders prior to sampling. (These will be replicates of each other and thus should be identical in size, shape, volume and composite material- 1L glass measuring cylinders are generally best)

2. Collect at least 2 litres of mixed liquor during sampling. (Collect enough mixed liquor to completely fill both the measuring cylinders)

3. Fill the measuring cylinders to the 1L mark with the mixed liquor and start a timer. (Make sure your mixed liquor sample is properly mixed before adding to the cylinders)

4. After 30 minutes, read the volume occupied by the settled sludge. (if the settled sludge is above the 350ml a dilution is required and will be referred to as dSVI)

5. Calculate the SVI by using the equation:

SVI = SV/MLSS × 1000ml

Notes: a. Freshly collected sludge should be used to accurately calculate the SVI. b. If a graduated cylinder of any other volume is used, it needs to be factored into the equation c. If a dSVI is performed, the dilution factor needs to be factored into the equation. SVI = SV/MLSS × 1000ml ×DF