2025 CWEA LAB ANALYST III EXAM QUESTIONS WITH
ANSWERS 2025/2026 GRADED A +
Chlorine, Total Residual - Bottle, Preservation, Hold Time - plastic/glass, unpres, 0.25hr
COD - Bottle, Preservation, Hold Time - plastic/glass, H2SO4 pH<2, 28 days
Color (Spec) - Bottle, Preservation, Hold Time - amber plastic/glass, unpres, 48 hr
Color (Vis) - Bottle, Preservation, Hold Time - amber plastic/glass, unpres, 24 hr
Cyanide - Bottle, Preservation, Hold Time - amber plastic/glass, absorbic acid(dechlor)
NaOH pH>11, 14 days
DOC - Bottle, Preservation, Hold Time - glass/voa, filter & pH<2 H3PO4, 28 days
HAA - Bottle, Preservation, Hold Time - amber glass, ammonium chloride, 14 days
Hardness - Bottle, Preservation, Hold Time - plastic/glass, pH<2 HNO3, 6 mo
1664/HEM - Bottle, Preservation, Hold Time - glass, ph<2 HCl/H2SO4, 28 days
HexChrom - Bottle, Preservation, Hold Time - plastic, ammonium sulfate/ammonium
hydroxide buffer (14 days), unpres (24 hrs)
Mercury - Bottle, Preservation, Hold Time - fluoropolymer, HCl, 28 days
Nitrate-Nitrite - Bottle, Preservation, Hold Time - plastic/glass, none, 48 hrs
TKN - Bottle, Preservation, Hold Time - amber plastic/glass, pH<2 H2SO4, 28 days
Odor - Bottle, Preservation, Hold Time - glass, unpres, 6 hrs
OP Pest / PCBS - Bottle, Preservation, Hold Time - amber glass, sodium thiosulfate, 7
days
Perchlorate - Bottle, Preservation, Hold Time - plastic/glass, unpres, 28 days
pH - Bottle, Preservation, Hold Time - plastic/glass, unpres, 0.25 hr
o-Phosphorus - Bottle, Preservation, Hold Time - glass voa, filter, 48 hrs
total Phosphorus - Bottle, Preservation, Hold Time - glass voa, pH<2 H2SO4, 28 days
Phthlates - Bottle, Preservation, Hold Time - amber glass, HCl pH<2, 7 days
, Settleable solids - Bottle, Preservation, Hold Time - plastic/glass, unpres, 48 hr
TSS/TDS/TS - Bottle, Preservation, Hold Time - plastic/glass, unpres, 7 days
EC - Bottle, Preservation, Hold Time - plastic/glass, unpres, 28 days
Sulfide - Bottle, Preservation, Hold Time - clear glass, zinc acetate pH>9 NaOH, 7 days
THM - Bottle, Preservation, Hold Time - amber voa, sod thiosulfate, 14 days
TOC - Bottle, Preservation, Hold Time - amber voa, pH>2 H3PO4, 28 days
Turbidity - Bottle, Preservation, Hold Time - glass/plastic, unpres, 48 hrs
UV254 - Bottle, Preservation, Hold Time - amber glass, unpres, 48 hrs
524 VOCS - Bottle, Preservation, Hold Time - amber voa, HCl pH>2 (abs acid if chlor),
14 days
624 VOCS - Bottle, Preservation, Hold Time - amber voa, unpres / sod thio (if chlor), 3
days
Coliform - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr
(fecal)/ 30 hr (total)
HPC - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr / 24
hrs
Enterrococci - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr
HPC - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr/24 hr
What does COLOR measure? - Amount of color units (CU) in a sample. Color caused
by natural metallic ions (Fe & Mg) & industrial wastes.
What is the test summary for COLOR? - Sample -> Tubes -> Compare to color
standards over light source
Which of the following techniques is used to isolate anionic surfactants (as MBAS) from
the sample matrix? - Extraction
In the cyanide determination, which one of the following is not an interference? -
Halogenated aromatics
Which of the following is not a major interference in phenol determination? - Hydroxy
derivatives of benzene
ANSWERS 2025/2026 GRADED A +
Chlorine, Total Residual - Bottle, Preservation, Hold Time - plastic/glass, unpres, 0.25hr
COD - Bottle, Preservation, Hold Time - plastic/glass, H2SO4 pH<2, 28 days
Color (Spec) - Bottle, Preservation, Hold Time - amber plastic/glass, unpres, 48 hr
Color (Vis) - Bottle, Preservation, Hold Time - amber plastic/glass, unpres, 24 hr
Cyanide - Bottle, Preservation, Hold Time - amber plastic/glass, absorbic acid(dechlor)
NaOH pH>11, 14 days
DOC - Bottle, Preservation, Hold Time - glass/voa, filter & pH<2 H3PO4, 28 days
HAA - Bottle, Preservation, Hold Time - amber glass, ammonium chloride, 14 days
Hardness - Bottle, Preservation, Hold Time - plastic/glass, pH<2 HNO3, 6 mo
1664/HEM - Bottle, Preservation, Hold Time - glass, ph<2 HCl/H2SO4, 28 days
HexChrom - Bottle, Preservation, Hold Time - plastic, ammonium sulfate/ammonium
hydroxide buffer (14 days), unpres (24 hrs)
Mercury - Bottle, Preservation, Hold Time - fluoropolymer, HCl, 28 days
Nitrate-Nitrite - Bottle, Preservation, Hold Time - plastic/glass, none, 48 hrs
TKN - Bottle, Preservation, Hold Time - amber plastic/glass, pH<2 H2SO4, 28 days
Odor - Bottle, Preservation, Hold Time - glass, unpres, 6 hrs
OP Pest / PCBS - Bottle, Preservation, Hold Time - amber glass, sodium thiosulfate, 7
days
Perchlorate - Bottle, Preservation, Hold Time - plastic/glass, unpres, 28 days
pH - Bottle, Preservation, Hold Time - plastic/glass, unpres, 0.25 hr
o-Phosphorus - Bottle, Preservation, Hold Time - glass voa, filter, 48 hrs
total Phosphorus - Bottle, Preservation, Hold Time - glass voa, pH<2 H2SO4, 28 days
Phthlates - Bottle, Preservation, Hold Time - amber glass, HCl pH<2, 7 days
, Settleable solids - Bottle, Preservation, Hold Time - plastic/glass, unpres, 48 hr
TSS/TDS/TS - Bottle, Preservation, Hold Time - plastic/glass, unpres, 7 days
EC - Bottle, Preservation, Hold Time - plastic/glass, unpres, 28 days
Sulfide - Bottle, Preservation, Hold Time - clear glass, zinc acetate pH>9 NaOH, 7 days
THM - Bottle, Preservation, Hold Time - amber voa, sod thiosulfate, 14 days
TOC - Bottle, Preservation, Hold Time - amber voa, pH>2 H3PO4, 28 days
Turbidity - Bottle, Preservation, Hold Time - glass/plastic, unpres, 48 hrs
UV254 - Bottle, Preservation, Hold Time - amber glass, unpres, 48 hrs
524 VOCS - Bottle, Preservation, Hold Time - amber voa, HCl pH>2 (abs acid if chlor),
14 days
624 VOCS - Bottle, Preservation, Hold Time - amber voa, unpres / sod thio (if chlor), 3
days
Coliform - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr
(fecal)/ 30 hr (total)
HPC - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr / 24
hrs
Enterrococci - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr
HPC - Bottle, Preservation, Hold Time - sterile plastic/glass, sod thiosulfate, 8 hr/24 hr
What does COLOR measure? - Amount of color units (CU) in a sample. Color caused
by natural metallic ions (Fe & Mg) & industrial wastes.
What is the test summary for COLOR? - Sample -> Tubes -> Compare to color
standards over light source
Which of the following techniques is used to isolate anionic surfactants (as MBAS) from
the sample matrix? - Extraction
In the cyanide determination, which one of the following is not an interference? -
Halogenated aromatics
Which of the following is not a major interference in phenol determination? - Hydroxy
derivatives of benzene
