CMA EXAM REVIEW QUESTIONS WITH
ACCURATE SOLUTIONS 2026
▶ What does conductivity measure? Answer: The ions in a solution
* inorganics = good conductors
* organics = poor conductors
-Estimate TDS (mg/L) in a sample
-Estimate cations or anions in a sample
▶ what is conductivity dependent on? Answer: temperature
▶ what units are used for conductivity Answer: micro-siemans / cm
▶ what is used to calibrate conductivity Answer: KCl
▶ How is conductivity measured? Answer: meters w/ platinum electrodes
▶ what temperature should conductivity be taken at? Answer: 25C
▶ Conductance Calculation Answer: G = k(A/L)
G: conductance
k: conductivity standard
A: electrode surface area (cm2)
L: distance between electrodes (cm)
▶ Conductivity hold time Answer: 4C for 28 days
▶ How is D.O preserved? Answer: w/o iodine demand: H2SO4 + MnSO4 +
alkali-iodide
-for a "few" hours
w/ iodine demand: H2SO4 + sodium azide
-for 4-8h
, ▶ D.O. hold time Answer: D.O. should be measured ASAP on samples w/
oxygen or iodine demand
▶ D.O. methods Answer: 1. titrimetric / idiometric (Winkler)
2. electrometric (probe)
▶ what is BOD? Answer: Biological oxygen demand
Carbonaceous + nitrogenous demand
the dissolved oxygen consumed by microbial life while assimilating and
oxidizing organic material in a sample
▶ Carbonaceous oxygen demand Answer: molecular oxygen used during a
set incubation period for the biochemical degradation of organic material
▶ Nitrogenous oxygen demand Answer: oxygen used to oxidize reduced
forms of nitrogen
▶ What nitrification inhibitors are used for the CBOD test? Answer: TCMP
or ATU
▶ What is the incubation temp & time period for a BOD test? Answer: 20C
+/- 1
5 days +/- 6h
▶ What is seeding? Answer: adding a population of microorganisms that
are capable of oxidizing the biodegradable organic matter in the sample
▶ Why must light be blocked in a BOD test? Answer: to prevent
photosynthetic oxygen production
▶ What are the units for BOD? Answer: mg/L
▶ BOD Calculation Answer: The reduction in DO during the incubation =
BOD
BOD mg/L = [(D1 - D2) - (S * Vs)] / P
D1 - initial DO
D2 - final DO
ACCURATE SOLUTIONS 2026
▶ What does conductivity measure? Answer: The ions in a solution
* inorganics = good conductors
* organics = poor conductors
-Estimate TDS (mg/L) in a sample
-Estimate cations or anions in a sample
▶ what is conductivity dependent on? Answer: temperature
▶ what units are used for conductivity Answer: micro-siemans / cm
▶ what is used to calibrate conductivity Answer: KCl
▶ How is conductivity measured? Answer: meters w/ platinum electrodes
▶ what temperature should conductivity be taken at? Answer: 25C
▶ Conductance Calculation Answer: G = k(A/L)
G: conductance
k: conductivity standard
A: electrode surface area (cm2)
L: distance between electrodes (cm)
▶ Conductivity hold time Answer: 4C for 28 days
▶ How is D.O preserved? Answer: w/o iodine demand: H2SO4 + MnSO4 +
alkali-iodide
-for a "few" hours
w/ iodine demand: H2SO4 + sodium azide
-for 4-8h
, ▶ D.O. hold time Answer: D.O. should be measured ASAP on samples w/
oxygen or iodine demand
▶ D.O. methods Answer: 1. titrimetric / idiometric (Winkler)
2. electrometric (probe)
▶ what is BOD? Answer: Biological oxygen demand
Carbonaceous + nitrogenous demand
the dissolved oxygen consumed by microbial life while assimilating and
oxidizing organic material in a sample
▶ Carbonaceous oxygen demand Answer: molecular oxygen used during a
set incubation period for the biochemical degradation of organic material
▶ Nitrogenous oxygen demand Answer: oxygen used to oxidize reduced
forms of nitrogen
▶ What nitrification inhibitors are used for the CBOD test? Answer: TCMP
or ATU
▶ What is the incubation temp & time period for a BOD test? Answer: 20C
+/- 1
5 days +/- 6h
▶ What is seeding? Answer: adding a population of microorganisms that
are capable of oxidizing the biodegradable organic matter in the sample
▶ Why must light be blocked in a BOD test? Answer: to prevent
photosynthetic oxygen production
▶ What are the units for BOD? Answer: mg/L
▶ BOD Calculation Answer: The reduction in DO during the incubation =
BOD
BOD mg/L = [(D1 - D2) - (S * Vs)] / P
D1 - initial DO
D2 - final DO
