GATE Environmental Science and Engineering Practice Quiz

Question 1

In the standard 5-day BOD test at 20°C, a diluted wastewater sample has an initial dissolved oxygen (DO) of 8.8 mg/L and a final DO after 5 days of 3.2 mg/L. If the decimal fraction of sample in the BOD bottle is 0.25 and seed correction is negligible, the BOD5 of the wastewater is:

Accepted Answer

22.4 mg/L

Question 2

A wastewater sample has measured BOD5 = 220 mg/L and COD = 180 mg/L. Which conclusion is most appropriate?

Accepted Answer

The data suggest analytical inconsistency or interference because COD should generally not be lower than BOD5

Question 3

A seeded dilution water blank shows DO depletion of 0.4 mg/L. A seeded diluted sample bottle containing 6% wastewater shows DO depletion of 3.4 mg/L. If the seed volume fraction is the same in both bottles, the corrected BOD5 of the wastewater is:

Accepted Answer

50 mg/L

Question 4

A wastewater has ultimate carbonaceous BOD, L0 = 240 mg/L, and first-order deoxygenation constant k (base e) = 0.23 d^-1 at 20°C. The carbonaceous BOD exerted in 5 days is closest to:

Accepted Answer

164 mg/L

GATE Environmental Science and Engineering — Mock tests

Full-length mock tests for GATE Environmental Science and Engineering are coming soon