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Education/Training + Get AlertsWASTEWATER
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 Sludge and Nutrient Removal, Third Edition, Chapter 8.
DRINKING WATER
By Drew Hoelscher
New groundwater sources are:
A. Required to conduct triggered source water monitoring as required by the SWTR and/or maintain 2-log inactivation for viruses.
B. Required to conduct triggered source water monitoring as required by the SWTR and/or maintain 4-log inactivation for viruses.
C. Required to conduct triggered source water monitoring as required by the GWR and/or maintain 2-log inactivation for viruses.
D. Required to conduct triggered source water monitoring as required by the GWR and/or maintain 4-log inactivation for viruses.
Answer: D. New groundwater sources placed in operation after Nov. 30, 2009 are required to implement triggered source water monitoring or provide at least 4-log inactivation/removal, or a state-approved combination of these technologies, and conduct compliance monitoring within 30 days of the source being put in service. More information pertaining to the groundwater rule (GWR) can be obtained at nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100156H.txt.
About the authors
Rick Lallish is water pollution control program director and Drew Hoelscher is program director of drinking water operations at the Environmental Resources Training Center of Southern Illinois University Edwardsville.
