A sample of sludge has an SS concentration of 4000 mg/L. After settling for 30 minutes in a 1 L cylinder, the sludge occupies 400 mL. The Sludge Volume Index is :
- A100Correct
- B50
- C200
- D150
Solution
Concept
SVI
Formula
SVI = V30 (mL/L) / MLSS (g/L)
Step-by-step solution
1. SVI = 400 mL/L ÷ 4 g/L = 100 mL/g.
Explanation
The sludge volume index is the volume in mL occupied by 1 g of activated sludge after 30 minutes of settling. SVI between 50 and 150 indicates good settling.
Why the other options are wrong
50, 150 and 200 do not equal 400/4.
Shortcut
SVI = settled volume per litre ÷ MLSS in g/L.
Common mistake
Using mg/L instead of g/L.
Correct answer: A) 100