u/FubarJackson145

So im studying for my PA wastewater certifaction and this question has had me stumped for hours and idk what im missing.

What is the sludge age given the following information:

• Raw TSS = 212 mg/l

• Flow = .47 MGD

• 2 aeration basins = 40 ft diameter x 15ft deep

• MLSS = 5651 mg/l

When i calc the aeration tank volume i get 18849.56 ft ^3 of water. Turn into millions of gallons, multiply that by 2, then take that × 5651 × 8.34= 1777 rounded up

Then do 0.47MGD × 212 × 8.34= 831 rounded up

I get 2.13 days which is WAAAAAY off and idk if im missing a step or just did something wrong. Any help is IMMENSLY appreciated. Other than vocab memorization these sludge age calcs have been the death of me