GATE CE 2022 Set 1 — Question 60
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Environmental Engineering → Wastewater Treatment Processes → BOD Kinetics
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Question
A 2 % sewage sample (in distilled water) was incubated for 3 days at 27 °C temperature. After incubation, a dissolved oxygen depletion of 10 mg/L was recorded. The biochemical oxygen demand (BOD) rate constant at 27 °C was found to be 0.23 day (at base ).The ultimate BOD (in mg/L) of the sewage will be_____________. (round off to the nearest integer)
Correct answer
1000 to 1005
Solution
1.Calculate the 3-day BOD (BOD) of the sewage:
BOD of diluted sample = DO depletion = 10 mg/L.Dilution factor = .
BOD of sewage = mg/L.
2.Use the BOD kinetics equation to find ultimate BOD ():
BODFor days and day:
mg/L.Rounding to the nearest integer, the ultimate BOD is 1003 mg/L.
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