INDIANA CERTIFIED OPERATOR
DRINKING WATER CLASS C
Exam Practice Questions
2026-2027 Edition
Verified Answers Plus Rationales
Q&A; | Instant Download PDF
EXAM SPECIFICATIONS
Time Allocation: 3 Hours
Total Questions: 100 Questions
Question Format: Multiple Choice with Rationales
Minimum Competency: 70% Required to Pass
Core Focus: Coagulation, Filtration, Disinfection, Distribution, Indiana Rules
Indiana Certified Operator Drinking Water Class C Exam Prep 2026-2027 Page 1
, Exam Overview & Content Outline
EXAM PURPOSE
Indiana Class C Water Operator certification covers small surface water or groundwater systems
serving 501-3,300 people. Based on Safe Drinking Water Act, Indiana 327 IAC 8, and IDEM
requirements for conventional treatment, distribution, monitoring, and compliance.
CONTENT DISTRIBUTION
• Coagulation, Flocculation, Sedimentation (25%) — Jar testing, coagulants, mixing, settling,
sludge handling
• Filtration & Disinfection (25%) — Rapid sand, membrane, GAC, chlorination, UV, ozone, CT
values
• Distribution & Hydraulics (20%) — Pumps, storage, pressure, mains, valves, hydrants, water
hammer, flushing
• Water Quality Monitoring (20%) — SDWA, MCLs, sampling, coliform, turbidity, DBPs,
lead/copper, CCR
• Indiana Regulations & Safety (10%) — 327 IAC 8, operator duties, recordkeeping, emergencies,
security
QUESTION FORMAT & SCORING
Each item presents four options. Correct answers are highlighted in green with checkmark (✓).
Every question includes detailed rationale with water treatment standards. IDEM requires 70% to
pass Class C exam.
STUDY STRATEGY
Master coagulation/flocculation chemistry and jar testing. Know filtration types and backwash
procedures. Understand disinfection CT calculations. Review distribution hydraulics and pump
curves. Study SDWA MCLs and monitoring requirements. Practice math: detention time, loading
rates, chemical dosing. Review Indiana 327 IAC 8.
CURRICULUM ALIGNMENT
Questions reflect 2026-2027 standards: EPA Safe Drinking Water Act, Indiana 327 IAC 8, IDEM
Drinking Water Branch, AWWA standards, 10 States Standards, and Surface Water Treatment Rule.
Indiana Certified Operator Drinking Water Class C Exam Prep 2026-2027 Page 2
, SECTION I: Coagulation, Flocculation, Sedimentation
1. Jar test determines:
A. Chlorine residual
✓ B. Optimal coagulant dose and pH
C. Turbidity only
D. Flow rate
Rationale: Jar test: Simulates coagulation/flocculation/sedimentation. Determines optimal coagulant type
(alum, ferric, polymer), dose, and pH. Six jars, varying doses, mix rapid (1 min), slow (20 min), settle (30
min). Measure turbidity, observe floc. Used to adjust plant feed. Critical for surface water treatment.
2. Alum (aluminum sulfate) optimal pH range:
A. 4.0-5.0
✓ B. 5.5-7.5
C. 9.0-10.0
D. 11-12
Rationale: Alum Al2(SO4)3: Optimal pH 5.5-7.5. Forms aluminum hydroxide floc. Below 5.5: soluble
aluminum. Above 7.5: poor floc. Consumes alkalinity: 0.5 mg/L per mg/L alum. May need lime/soda ash.
Ferric chloride: wider pH 4-11. Jar test determines. Indiana surface water plants use.
3. Rapid mix detention time:
A. 30 minutes
✓ B. 30 seconds to 2 minutes
C. 4 hours
D. 24 hours
Rationale: Rapid mix: 30 seconds to 2 minutes detention, high G-value 300-1000 s-1. Disperses coagulant,
destabilizes particles. Flash mix. Followed by flocculation: 20-30 min, low G 20-80 s-1, gentle mixing forms
floc. Then sedimentation: 2-4 hours. Proper detention critical for treatment.
4. Sludge from sedimentation basin is:
A. Discharged to stream
✓ B. Dewatered and disposed per regulations
C. Recycled to headworks
D. Left in basin
Rationale: Sludge: Settled solids, alum/ferric hydroxides, turbidity. Dewater via lagoons, drying beds,
mechanical. Dispose: landfill, land application if approved. Cannot discharge to waterway without NPDES
permit. Beneficial reuse possible. Sludge volume 0.1-1% of flow. Indiana regulations apply.
5. Turbidity removal in conventional treatment occurs primarily in:
A. Chlorination
✓ B. Sedimentation and filtration
C. Aeration
Indiana Certified Operator Drinking Water Class C Exam Prep 2026-2027 Page 3
DRINKING WATER CLASS C
Exam Practice Questions
2026-2027 Edition
Verified Answers Plus Rationales
Q&A; | Instant Download PDF
EXAM SPECIFICATIONS
Time Allocation: 3 Hours
Total Questions: 100 Questions
Question Format: Multiple Choice with Rationales
Minimum Competency: 70% Required to Pass
Core Focus: Coagulation, Filtration, Disinfection, Distribution, Indiana Rules
Indiana Certified Operator Drinking Water Class C Exam Prep 2026-2027 Page 1
, Exam Overview & Content Outline
EXAM PURPOSE
Indiana Class C Water Operator certification covers small surface water or groundwater systems
serving 501-3,300 people. Based on Safe Drinking Water Act, Indiana 327 IAC 8, and IDEM
requirements for conventional treatment, distribution, monitoring, and compliance.
CONTENT DISTRIBUTION
• Coagulation, Flocculation, Sedimentation (25%) — Jar testing, coagulants, mixing, settling,
sludge handling
• Filtration & Disinfection (25%) — Rapid sand, membrane, GAC, chlorination, UV, ozone, CT
values
• Distribution & Hydraulics (20%) — Pumps, storage, pressure, mains, valves, hydrants, water
hammer, flushing
• Water Quality Monitoring (20%) — SDWA, MCLs, sampling, coliform, turbidity, DBPs,
lead/copper, CCR
• Indiana Regulations & Safety (10%) — 327 IAC 8, operator duties, recordkeeping, emergencies,
security
QUESTION FORMAT & SCORING
Each item presents four options. Correct answers are highlighted in green with checkmark (✓).
Every question includes detailed rationale with water treatment standards. IDEM requires 70% to
pass Class C exam.
STUDY STRATEGY
Master coagulation/flocculation chemistry and jar testing. Know filtration types and backwash
procedures. Understand disinfection CT calculations. Review distribution hydraulics and pump
curves. Study SDWA MCLs and monitoring requirements. Practice math: detention time, loading
rates, chemical dosing. Review Indiana 327 IAC 8.
CURRICULUM ALIGNMENT
Questions reflect 2026-2027 standards: EPA Safe Drinking Water Act, Indiana 327 IAC 8, IDEM
Drinking Water Branch, AWWA standards, 10 States Standards, and Surface Water Treatment Rule.
Indiana Certified Operator Drinking Water Class C Exam Prep 2026-2027 Page 2
, SECTION I: Coagulation, Flocculation, Sedimentation
1. Jar test determines:
A. Chlorine residual
✓ B. Optimal coagulant dose and pH
C. Turbidity only
D. Flow rate
Rationale: Jar test: Simulates coagulation/flocculation/sedimentation. Determines optimal coagulant type
(alum, ferric, polymer), dose, and pH. Six jars, varying doses, mix rapid (1 min), slow (20 min), settle (30
min). Measure turbidity, observe floc. Used to adjust plant feed. Critical for surface water treatment.
2. Alum (aluminum sulfate) optimal pH range:
A. 4.0-5.0
✓ B. 5.5-7.5
C. 9.0-10.0
D. 11-12
Rationale: Alum Al2(SO4)3: Optimal pH 5.5-7.5. Forms aluminum hydroxide floc. Below 5.5: soluble
aluminum. Above 7.5: poor floc. Consumes alkalinity: 0.5 mg/L per mg/L alum. May need lime/soda ash.
Ferric chloride: wider pH 4-11. Jar test determines. Indiana surface water plants use.
3. Rapid mix detention time:
A. 30 minutes
✓ B. 30 seconds to 2 minutes
C. 4 hours
D. 24 hours
Rationale: Rapid mix: 30 seconds to 2 minutes detention, high G-value 300-1000 s-1. Disperses coagulant,
destabilizes particles. Flash mix. Followed by flocculation: 20-30 min, low G 20-80 s-1, gentle mixing forms
floc. Then sedimentation: 2-4 hours. Proper detention critical for treatment.
4. Sludge from sedimentation basin is:
A. Discharged to stream
✓ B. Dewatered and disposed per regulations
C. Recycled to headworks
D. Left in basin
Rationale: Sludge: Settled solids, alum/ferric hydroxides, turbidity. Dewater via lagoons, drying beds,
mechanical. Dispose: landfill, land application if approved. Cannot discharge to waterway without NPDES
permit. Beneficial reuse possible. Sludge volume 0.1-1% of flow. Indiana regulations apply.
5. Turbidity removal in conventional treatment occurs primarily in:
A. Chlorination
✓ B. Sedimentation and filtration
C. Aeration
Indiana Certified Operator Drinking Water Class C Exam Prep 2026-2027 Page 3
