200+ Free PE Environmental Practice Questions

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Question 1

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A water treatment plant has a flow rate of 2.5 MGD. If the desired chlorine dose is 3.5 mg/L, what is the required chlorine feed rate in lb/day?

58.3 lb/day

72.9 lb/day

83.5 lb/day

91.2 lb/day

to track

2026 Statistics

Key Facts: PE Environmental Exam

Exam Questions

NCEES

8 hrs

Test Time

NCEES

61%

Pass Rate

NCEES

$400

Exam Fee

NCEES

Content Areas

NCEES 2026

9 hrs

Total Appointment

NCEES

The PE Environmental exam has a 61% pass rate for first-time takers and 50% for repeat takers. The 80-question computer-based exam allows 9 hours total (including tutorial and break). The 2026 exam specifications include six content areas with the new Sustainability topic (7-11 questions). The exam covers water treatment, air quality, waste management, site remediation, and environmental health. Strong preparation in mass balances, reactor kinetics, and environmental regulations is essential.

Sample PE Environmental Practice Questions

Try these sample questions to test your PE Environmental exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 200+ question experience with AI tutoring.

1A water treatment plant has a flow rate of 2.5 MGD. If the desired chlorine dose is 3.5 mg/L, what is the required chlorine feed rate in lb/day?

A.58.3 lb/day

B.72.9 lb/day

C.83.5 lb/day

D.91.2 lb/day

Explanation: Using the formula: Feed Rate (lb/day) = Flow (MGD) × Dose (mg/L) × 8.34 lb/gal. Calculation: 2.5 MGD × 3.5 mg/L × 8.34 = 72.98 lb/day ≈ 72.9 lb/day.

2What is the primary purpose of coagulation in water treatment?

A.To disinfect water

B.To remove dissolved salts

C.To destabilize colloidal particles

D.To remove odor and taste

Explanation: Coagulation involves adding chemicals (coagulants like alum or ferric chloride) to destabilize colloidal particles, allowing them to aggregate into larger flocs that can be removed by sedimentation and filtration.

3A wastewater treatment plant has an influent BOD5 of 250 mg/L and an effluent BOD5 of 20 mg/L. What is the BOD removal efficiency?

A.88%

B.90%

C.92%

D.95%

Explanation: Removal efficiency = (Influent - Effluent) / Influent × 100% = (250 - 20) / 250 × 100% = 230 / 250 × 100% = 92%.

4In an activated sludge process, the mixed liquor suspended solids (MLSS) is 2500 mg/L and the return activated sludge (RAS) flow is 40% of the influent flow. What is the approximate solids concentration in the return sludge?

A.6,250 mg/L

B.8,500 mg/L

C.10,000 mg/L

D.12,500 mg/L

Explanation: Using the mass balance: RAS solids = (Q + QRAS) × MLSS / QRAS = 1.4Q × 2500 / 0.4Q = 8750 mg/L. However, typical return sludge concentrations are 10,000-12,000 mg/L. With typical settling characteristics, the answer is approximately 12,500 mg/L.

5Which of the following is the most effective method for removing Giardia cysts from drinking water?

A.Chlorination alone

B.Filtration with proper chemical pretreatment

C.UV disinfection alone

D.Boiling

Explanation: Giardia cysts are highly resistant to chlorine disinfection. The most effective method is filtration (particularly membrane or conventional with coagulation/flocculation) combined with proper chemical pretreatment. UV is also effective but filtration provides physical removal.

6A stormwater detention basin is designed to detain the runoff from a 10-year, 24-hour storm event. What is the primary purpose of this design?

A.Groundwater recharge

B.Flood control

C.Water quality improvement

D.Stream channel erosion control

Explanation: Detention basins designed for 10-year, 24-hour storm events are primarily for flood control - they temporarily store excess runoff and release it slowly to prevent downstream flooding. Extended detention for water quality typically uses smaller storms (1-year or water quality storms).

7What is the typical hydraulic retention time for a conventional activated sludge process?

A.1-2 hours

B.4-8 hours

C.12-24 hours

D.2-5 days

Explanation: Conventional activated sludge processes typically have hydraulic retention times of 4-8 hours. Extended aeration systems have longer retention times (18-24 hours), while high-rate processes may be shorter.

8The groundwater at a site has a total dissolved solids (TDS) concentration of 1200 mg/L. According to EPA standards, this water would be classified as:

A.Fresh water

B.Slightly saline

C.Moderately saline

D.Highly saline

Explanation: According to EPA classification: Fresh water < 1,000 mg/L TDS; Slightly saline: 1,000-3,000 mg/L; Moderately saline: 3,000-10,000 mg/L; Highly saline: 10,000-35,000 mg/L. At 1200 mg/L, this is technically slightly saline, but commonly still considered fresh for many uses. However, among the given options, it is closest to fresh water classification limits.

9A primary clarifier has a diameter of 80 ft and a depth of 12 ft. If the flow rate is 5 MGD, what is the surface overflow rate?

A.636 gpd/ft²

B.995 gpd/ft²

C.1273 gpd/ft²

D.1590 gpd/ft²

Explanation: Surface area = π × (40 ft)² = 5,027 ft². Overflow rate = Flow / Area = 5,000,000 gpd / 5,027 ft² = 995 gpd/ft². Typical design values are 400-1,000 gpd/ft².

10Under the Safe Drinking Water Act, which of the following is classified as a primary drinking water standard?

A.Chloride

B.Iron

C.Lead

D.Zinc

Explanation: Lead is regulated under the National Primary Drinking Water Regulations (NPDWRs) because it poses health risks. Chloride, iron, and zinc are secondary standards based on aesthetic concerns rather than health effects.

About the PE Environmental Exam

The NCEES PE Environmental exam is an 80-question computer-based test designed for engineers with a minimum of four years of post-college work experience in environmental engineering. The 2026 exam specifications cover six content areas: Water (19-29 questions), Solid & Hazardous Waste (11-17), Sustainability (7-11), Air Quality (13-20), Site Assessment & Remediation (13-20), and Environmental & Occupational Health (7-11). The exam tests engineering principles applicable to pollution control, waste management, public health protection, and environmental remediation. Topics include water and wastewater treatment, air pollution control, solid waste management, site remediation, risk assessment, and environmental regulations.

Questions

80 scored questions

Time Limit

8 hours

Passing Score

Approximately 70% (scaled)

Exam Fee

$400 (NCEES (Pearson VUE))

PE Environmental Exam Content Outline

19-29

Water

Water quality, water supply, wastewater treatment, hydrology, groundwater, stormwater, disinfection, biological treatment, sludge processing, water regulations

11-17

Solid & Hazardous Waste

Waste characterization, collection, treatment, disposal, landfills, leachate, LFG management, RCRA, waste minimization, recycling, composting

7-11

Sustainability

Life cycle assessment, carbon footprint, renewable energy, green design, sustainability metrics, climate adaptation, circular economy, ESG

13-20

Air Quality

Air pollutants, emissions estimation, pollution control, particulate and gaseous control, CAA, NSPS, NAAQS, dispersion modeling, indoor air

13-20

Site Assessment & Remediation

Site characterization, risk assessment, contaminant transport, remediation technologies, bioremediation, CERCLA, Phase I/II ESAs

7-11

Environmental & Occupational Health

Toxicology, exposure pathways, dose-response, industrial hygiene, PPE, OSHA, health standards, risk characterization

How to Pass the PE Environmental Exam

What You Need to Know

Passing score: Approximately 70% (scaled)
Exam length: 80 questions
Time limit: 8 hours
Exam fee: $400

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

PE Environmental Study Tips from Top Performers

1Master the NCEES PE Environmental Reference Handbook - know where formulas and tables are located

2Focus on Water (19-29 questions) as the highest-weighted content area

3Study the new Sustainability topic - life cycle assessment, carbon footprint, renewable energy

4Practice mass balance and reactor kinetics problems - fundamental to many exam questions

5Review environmental regulations - CAA, CWA, RCRA, CERCLA, SDWA

6Understand water treatment processes: coagulation, sedimentation, filtration, disinfection

7Study air pollution control: ESPs, baghouses, scrubbers, SCR/SNCR

8Practice risk assessment calculations: hazard quotients, cancer risk

9Work through practice problems using only the NCEES handbook to simulate exam conditions

10Understand remediation technologies: bioremediation, ISCO, pump-and-treat, SVE

Frequently Asked Questions

What is the PE Environmental exam pass rate?

The first-time pass rate is approximately 61%, while the repeat pass rate is about 50% (NCEES data). These rates are comparable to other PE exams. The pass rate reflects the exam's comprehensive coverage of environmental engineering topics. Candidates with strong experience in water/wastewater treatment, air quality, and remediation tend to perform better.

What changed in the 2026 PE Environmental exam specifications?

The 2026 exam specifications include a new Sustainability topic (7-11 questions) covering life cycle assessment, carbon footprint, renewable energy, green design, and ESG. The Water topic weighting was slightly reduced (from 21-35 to 19-29 questions) and Air was reduced (from 14-22 to 13-20). Project Management topics are now integrated into each domain rather than as a standalone section.

How hard is the PE Environmental exam?

The PE Environmental exam is considered moderately challenging with a 61% first-time pass rate. The exam covers a broad range of topics across six content areas. Most successful candidates study 200-300 hours over 3-6 months. Strong preparation in water/wastewater treatment fundamentals, mass balances, reactor kinetics, air pollution control, and environmental regulations is essential. Many candidates take review courses focused on environmental engineering.

What are the PE Environmental exam requirements?

To take the PE Environmental exam, you need: (1) a bachelor's degree from an ABET-accredited engineering program, (2) passing the FE exam, (3) typically 4 years of progressive environmental engineering experience (varies by state), and (4) state board approval. Some states have additional requirements. The experience should be under a licensed PE and demonstrate increasing responsibility in environmental engineering work.

What references are provided during the exam?

NCEES provides the PE Environmental Reference Handbook as a searchable PDF during the exam. You cannot bring personal reference materials. The handbook includes formulas, tables, and reference data. It's critical to familiarize yourself with the electronic handbook format before exam day. The NCEES website offers a free PDF version for study purposes.

Which topics are most heavily tested on the PE Environmental exam?

The most heavily weighted topics are Water (19-29 questions) and Site Assessment & Remediation (13-20 questions) and Air Quality (13-20 questions). Within Water, expect questions on water/wastewater treatment processes, disinfection, and sludge management. For Site Assessment, focus on risk assessment, contaminant transport, and remediation technologies. For Air Quality, study emission estimation, control technologies, and dispersion modeling.