Calculators / Percent Removal
Percent Removal calculator
Percent removal compares what came in with what went out. Exams ask it for BOD, TSS and individual units like primary clarifiers.
% Removal = (In − Out) ÷ In × 100
Worked example
Influent BOD is 220 mg/L and effluent BOD is 18 mg/L. What is the percent BOD removal?
- (220 − 18) ÷ 220 × 100 = 91.8%
Answer: 91.8%
Common mistakes
- Dividing by the effluent instead of the influent.
Check your exam's reference sheet for its exact constants. Some use 3.14 instead of 3.1416, which changes answers in the last digit.