Question

Sludge bulking in an activated sludge process is mainly due to

• A. High dissolved oxygen
• B. Low sludge age
• C. Excessive growth of filamentous microorganisms
• D. High settling velocity

Hint:

Bulking sludge: \[ \boxed{ \text{Filamentous bacterial growth} \rightarrow \text{Poor settling} \rightarrow \text{High SVI} } \]

Answer 1

The Correct Option is C

Step 1: Recall what good floc looks like.
A healthy activated sludge floc is dense and compact, made mostly of floc forming bacteria, and it settles quickly.
Step 2: See what changes with filamentous growth.
When filamentous organisms multiply excessively, they stick out of the floc like a net, keeping flocs apart and trapping water inside the sludge mass.
Step 3: Connect this to bulking.
This loose, water trapping structure settles slowly and takes up a large volume, which is exactly what is termed sludge bulking.
\[ \boxed{\text{Excessive growth of filamentous microorganisms}} \]