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Practice Math Problems Questions

Math ProblemsQuestion 1 of 60

During the daily settleability test, a 1-L graduated cylinder of mixed liquor settles to 300 mL after 30 minutes (SV30 = 300 mL/L). The flow to the secondary clarifiers is 2.5 MGD. Using the common 30-minute settled volume method, estimate the return activated sludge (RAS) pumping rate in gpm. (Extraneous data: MLSS = 2,800 mg/L; WAS flow = 80 gpm; WAS TSS = 8,000 mg/L.) Reference: 1 MGD = 694.4 gpm. Approximate RAS fraction of influent flow: RAS% ≈ SV30 / (1000 − SV30).