Certified Water Treatment Systems
Technician (CWTST) – 2026 Practice
Examination|||questions and answers
with rationales/graded A+/2026
update/100% correct /instant
download
Total Questions: 85
Time Allowed: 2.5 hours
Passing Score: 70%
Instructions: Select the single best answer for each question. Correct answers
are highlighted in bold. A rationale follows each question.
Section A: Regulatory Framework & Safety (Q1–15)
1. Which federal regulation establishes the Maximum Contaminant Levels (MCLs)
for drinking water in the United States, as updated in 2026 to include stricter limits
for PFAS?
a) Clean Water Act (CWA)
b) Safe Drinking Water Act (SDWA)
c) Safe Drinking Water Act (SDWA) with 2026 PFAS Rule
d) Resource Conservation and Recovery Act (RCRA)
*Rationale: The SDWA authorizes EPA to set MCLs. The 2026 PFAS Rule lowers
combined PFOA+PFOS MCL to 4 ppt.*
2. According to OSHA 1910.134, what is the minimum acceptable oxygen
concentration for entering a confined space such as a clearwell?
a) 18.5%
b) 19.5%
c) 20.9%
d) 21.5%
,*Rationale: OSHA requires 19.5%–23.5% oxygen for safe entry. Below 19.5% is
oxygen-deficient.*
3. Which of the following is a 2026 EPA-approved method for on-line continuous
monitoring of Legionella pneumophila in treated water?
a) Heterotrophic plate count (HPC)
b) Rapid qPCR with automated sampling
c) Most Probable Number (MPN)
d) Membrane filtration
*Rationale: 2026 guidelines approve automated qPCR for real-time Legionella
surveillance in large buildings.*
4. The Hazard Analysis and Critical Control Points (HACCP) approach in water
treatment prioritizes:
a) Final product testing only
b) Preventative control of hazards at specific points
c) Operator daily logs
d) Emergency response plans
Rationale: HACCP identifies CCPs where control prevents, eliminates, or reduces
hazards.
5. Chlorine gas cylinder storage rooms must have a scrubber system capable of
neutralizing a leak of at least:
a) 100 ppm
b) 500 ppm
c) 1500 ppm
d) 5000 ppm
Rationale: 2026 uniform fire code requires capacity to handle 1500 ppm chlorine
release within 10 minutes.
6. A facility exceeds its permitted daily flow of backwash water. Which 2026
compliance approach is acceptable?
a) Divert untreated backwash to storm drain
b) Increase chlorine dose in backwash
c) Install on-site backwash recycling with membrane treatment
d) Store backwash in open lagoon with no liner
*Rationale: 2026 NPDES updates require recycling with treatment (e.g., UF/MF)
to zero liquid discharge for backwash.*
, 7. What is the maximum contaminant level goal (MCLG) for lead in drinking
water per 2026 revisions?
a) 15 ppb
b) Zero
c) 5 ppb
d) 10 ppb
*Rationale: MCLG is always zero for lead because it is a non-threshold toxin.
Action level remains 15 ppb.*
8. Which personal protective equipment (PPE) is mandatory when handling bulk
sodium hypochlorite (12.5% NaOCl) per 2026 GHS update?
a) Leather gloves and safety glasses
b) N95 mask and cotton coveralls
c) Chemical-resistant gloves, face shield, and neoprene apron
d) Hearing protection only
Rationale: NaOCl is corrosive and oxidizer; updated GHS requires full chemical
splash protection.
9. A water system has 3 consecutive months of total coliform presence in <5% of
monthly samples. Under Revised Total Coliform Rule (RTCR) 2026, the system is
in:
a) No violation
b) Acute violation (if E. coli positive) – but here, not acute, but monitoring
violation triggered
c) Monitoring violation
d) Treatment technique violation
Rationale: Presence of total coliform triggers repeat sampling. Only E. coli is
acute. Question tests distinction.
10. In 2026, which emerging contaminant group is added to the Unregulated
Contaminant Monitoring Rule (UCMR 6)?
a) Microplastics
b) 1,4-dioxane
c) Per- and polyfluoroalkyl substances (PFAS) – broader suite (30 compounds)
d) Pharmaceuticals
Rationale: UCMR 6 (2026) expands PFAS monitoring to 30 compounds including
GenX and PFBS.
Technician (CWTST) – 2026 Practice
Examination|||questions and answers
with rationales/graded A+/2026
update/100% correct /instant
download
Total Questions: 85
Time Allowed: 2.5 hours
Passing Score: 70%
Instructions: Select the single best answer for each question. Correct answers
are highlighted in bold. A rationale follows each question.
Section A: Regulatory Framework & Safety (Q1–15)
1. Which federal regulation establishes the Maximum Contaminant Levels (MCLs)
for drinking water in the United States, as updated in 2026 to include stricter limits
for PFAS?
a) Clean Water Act (CWA)
b) Safe Drinking Water Act (SDWA)
c) Safe Drinking Water Act (SDWA) with 2026 PFAS Rule
d) Resource Conservation and Recovery Act (RCRA)
*Rationale: The SDWA authorizes EPA to set MCLs. The 2026 PFAS Rule lowers
combined PFOA+PFOS MCL to 4 ppt.*
2. According to OSHA 1910.134, what is the minimum acceptable oxygen
concentration for entering a confined space such as a clearwell?
a) 18.5%
b) 19.5%
c) 20.9%
d) 21.5%
,*Rationale: OSHA requires 19.5%–23.5% oxygen for safe entry. Below 19.5% is
oxygen-deficient.*
3. Which of the following is a 2026 EPA-approved method for on-line continuous
monitoring of Legionella pneumophila in treated water?
a) Heterotrophic plate count (HPC)
b) Rapid qPCR with automated sampling
c) Most Probable Number (MPN)
d) Membrane filtration
*Rationale: 2026 guidelines approve automated qPCR for real-time Legionella
surveillance in large buildings.*
4. The Hazard Analysis and Critical Control Points (HACCP) approach in water
treatment prioritizes:
a) Final product testing only
b) Preventative control of hazards at specific points
c) Operator daily logs
d) Emergency response plans
Rationale: HACCP identifies CCPs where control prevents, eliminates, or reduces
hazards.
5. Chlorine gas cylinder storage rooms must have a scrubber system capable of
neutralizing a leak of at least:
a) 100 ppm
b) 500 ppm
c) 1500 ppm
d) 5000 ppm
Rationale: 2026 uniform fire code requires capacity to handle 1500 ppm chlorine
release within 10 minutes.
6. A facility exceeds its permitted daily flow of backwash water. Which 2026
compliance approach is acceptable?
a) Divert untreated backwash to storm drain
b) Increase chlorine dose in backwash
c) Install on-site backwash recycling with membrane treatment
d) Store backwash in open lagoon with no liner
*Rationale: 2026 NPDES updates require recycling with treatment (e.g., UF/MF)
to zero liquid discharge for backwash.*
, 7. What is the maximum contaminant level goal (MCLG) for lead in drinking
water per 2026 revisions?
a) 15 ppb
b) Zero
c) 5 ppb
d) 10 ppb
*Rationale: MCLG is always zero for lead because it is a non-threshold toxin.
Action level remains 15 ppb.*
8. Which personal protective equipment (PPE) is mandatory when handling bulk
sodium hypochlorite (12.5% NaOCl) per 2026 GHS update?
a) Leather gloves and safety glasses
b) N95 mask and cotton coveralls
c) Chemical-resistant gloves, face shield, and neoprene apron
d) Hearing protection only
Rationale: NaOCl is corrosive and oxidizer; updated GHS requires full chemical
splash protection.
9. A water system has 3 consecutive months of total coliform presence in <5% of
monthly samples. Under Revised Total Coliform Rule (RTCR) 2026, the system is
in:
a) No violation
b) Acute violation (if E. coli positive) – but here, not acute, but monitoring
violation triggered
c) Monitoring violation
d) Treatment technique violation
Rationale: Presence of total coliform triggers repeat sampling. Only E. coli is
acute. Question tests distinction.
10. In 2026, which emerging contaminant group is added to the Unregulated
Contaminant Monitoring Rule (UCMR 6)?
a) Microplastics
b) 1,4-dioxane
c) Per- and polyfluoroalkyl substances (PFAS) – broader suite (30 compounds)
d) Pharmaceuticals
Rationale: UCMR 6 (2026) expands PFAS monitoring to 30 compounds including
GenX and PFBS.
