WASTEWATER By Rick Lallish
What is the maximum blanket level in a secondary (activated sludge) clarifier?
A. 5%
B. 10%
C. 25%
D. 50%
Answer: C. Basic operation and knowledge of clarifier process controls are fundamentals that most operators should understand. In activated sludge processes, the sludge blanket should never exceed 25% of the sidewall depth of the secondary clarifier. In some texts, a 2-foot blanket is recommended. Whenever the blanket approaches or exceeds this depth, operators should take precautions. This is usually an indicator of problems such as filamentous bulking or equipment malfunction. The blanket should be checked daily, preferably at about the same time
