Field Office Compliance - Assistance

Assistance ID - 131607

City Of Dubuque Water Pollution Control Plant - 310201531

795 JULIEN DUBUQUE DR. Dubuque, IA 52003

Dubuque County

FO 1

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Attached Files/Reports

File Name	File Type	File Date	Note

Comments

Date	Comment	Commenter
6/17/2024	Called to discuss CBOD and TSS 30 day and 7 day exceedances. Sent in additional information - "Michele, While wet weather certainly exacerbated our operational challenges, I believe there were several contributors: Growth of filamentous bacteria hindered settling of solids in final clarification. This caused excessive solids to build up in the final clarifiers (generally, when calculating the food to microorganism ratio, we only consider the solids under aeration), while the mixed liquor concentration remained fairly steady. After collecting a sample (using a sludge judge) of the entire water column, of the final clarifiers, we discovered the total mass of microbes in the aeration basins and final clarifiers was much higher than expected. We began RAS chlorination to control filaments; we increased the wasting rate to gradually reduce the mass of solids under aeration; we increased the return activated sludge pumping rate to reduce the impacts of sludge bulking. I’ve included the following chart, of our Sludge Volume Index, which shows the SVI trend, in mL/g, from February through today. As the chart shows, the SVI has been steadily improving since mid-May."	MICHELE SMITH

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