Question

A high Sludge Volume Index (SVI) in an Activated Sludge Process (ASP) indicates

• A. Good sludge settling
• B. Compact floc formation
• C. Excess oxygen transfer
• D. Poor settling characteristics of sludge

Hint:

Interpretation of SVI: \[ \boxed{ \begin{aligned} \text{Low SVI} &\rightarrow \text{Good settling}\\ \text{High SVI} &\rightarrow \text{Bulking sludge / Poor settling} \end{aligned} } \]

Answer 1

The Correct Option is D

Step 1: Recall what SVI measures.
Sludge Volume Index is the volume in mL occupied by one gram of sludge solids after settling for 30 minutes.
Step 2: Think about what a high value means physically.
If the sludge takes up a large volume for a given mass, the floc is loose and bulky rather than dense and compact.
Step 3: Connect this to settling behaviour.
Bulky, loose floc settles slowly and does not compact well in the clarifier, which is exactly what poor settling means.
\[ \boxed{\text{Poor settling characteristics of sludge}} \]