CWEA GRADE 1 LAB ANALYST EXAM ACTUAL EXAM
2025/2026 200 QUESTIONS AND CORRECT DETAILED
ANSWERS WITH RATIONALES |GRADED A+
Question:1
What methods are used for measuring the DO content of samples -
ANSWER-The wrinkler or iodometric method and its modifications
and the membrane electrode
Question:2
Which modification of the wrinkled test is used for biological flocs with
high oxygen utilization rates - ANSWER-CuSO4-sulfamic acid
Question:3
If there is DO present in a BOD sample, what color will the floc turn
after the alkaline iodide-sodium azide solution is added - ANSWER-
Brown
Question:4
BOD Calulation in mg/L - ANSWER-(Initial DO mg/L - final DO mg/L) /
(sample volume mL/Bottle Volume mL)
1|P a g e
, Question:5
A DO sample to be analyzed by the wrinkled method, which is acidified
in the field, may be help for... - ANSWER-8 hrs
Question:6
To prepare a zero DO standard for membrane electrode test add... -
ANSWER-Excess NaSO3 and CoCl2
Question:7
In determining COD by the dichromate reflux method, the endpoint of
the titration is reached when.. - ANSWER-Ferrous ions are no longer
oxidized by the residual dichromate and the presence of
phenanthroline forms a red complex
Question:8
In CBOD test, 2-chloride-6-(trichloromethyl) pyridine is used to
suppress... - ANSWER-Nitrification
Question:9
The water quality for BOD dilution and reagent water should be.. -
ANSWER-Type 1
2|P a g e
2025/2026 200 QUESTIONS AND CORRECT DETAILED
ANSWERS WITH RATIONALES |GRADED A+
Question:1
What methods are used for measuring the DO content of samples -
ANSWER-The wrinkler or iodometric method and its modifications
and the membrane electrode
Question:2
Which modification of the wrinkled test is used for biological flocs with
high oxygen utilization rates - ANSWER-CuSO4-sulfamic acid
Question:3
If there is DO present in a BOD sample, what color will the floc turn
after the alkaline iodide-sodium azide solution is added - ANSWER-
Brown
Question:4
BOD Calulation in mg/L - ANSWER-(Initial DO mg/L - final DO mg/L) /
(sample volume mL/Bottle Volume mL)
1|P a g e
, Question:5
A DO sample to be analyzed by the wrinkled method, which is acidified
in the field, may be help for... - ANSWER-8 hrs
Question:6
To prepare a zero DO standard for membrane electrode test add... -
ANSWER-Excess NaSO3 and CoCl2
Question:7
In determining COD by the dichromate reflux method, the endpoint of
the titration is reached when.. - ANSWER-Ferrous ions are no longer
oxidized by the residual dichromate and the presence of
phenanthroline forms a red complex
Question:8
In CBOD test, 2-chloride-6-(trichloromethyl) pyridine is used to
suppress... - ANSWER-Nitrification
Question:9
The water quality for BOD dilution and reagent water should be.. -
ANSWER-Type 1
2|P a g e
