WASTEWATER
By: Rick Lallish
It is generally accepted that the sludge blanket depth in secondary clarifiers should not exceed 2 feet (0.6 meters). By allowing a deeper sludge blanket, what undesirable outcome may occur?
A. Nitrification may occur in the secondary clarifier.
B. Deeper blankets inhibit settleability of the sludge.
C. Premature digestion will occur in the secondary clarifier.
D. Solids may be washed out and into the effluent flow.
Answer: D. Monitoring of the sludge blanket is a key process control parameter. The rule of thumb is never to allow the sludge blanket to reach more than 25 percent of the clarifier sidewall. By
