WASTEWATER
By Rick Lallish
Denitrification in the secondary clarifier is undesirable. Which is the best method of minimizing denitrification of secondary clarifier sludge?
A. Proper wasting methods
B. Proper RAS controls
C. Maintaining elevated SRT levels
D. Maintaining higher HRT levels
Answer: B. Maintaining a consistent and controllable sludge blanket in the secondary clarifier by controlling the RAS rates in the activated sludge process is typically the best method. Higher HRT and elevated SRT rates are detrimental methods for this application. Denitrification of sludge in the secondary clarifier should be minimized to avoid negative effects to the final effluent. More information may be found in the WEF Manual, Activated
