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Exam Review

Key Facts: PE Environmental Exam

80

Exam Questions

NCEES

8 hrs

Test Time

NCEES

73%

First-Time Pass Rate

NCEES

$400

Exam Fee

NCEES

6

Content Areas

NCEES 2026

9 hrs

Total Appointment

NCEES

The PE Environmental exam had a 73% first-time and 54% repeat pass rate in NCEES's July 2026 table. 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 review concepts for the PE Environmental exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 302+ 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.73.0 lb/day
C.83.5 lb/day
D.91.2 lb/day
Explanation: Feed rate (lb/day) = Flow (MGD) x Dose (mg/L) x 8.34 lb/gal. Calculation: 2.5 MGD x 3.5 mg/L x 8.34 = 72.98 lb/day, which rounds to 73.0 lb/day of pure chlorine. If a hypochlorite product were used, this value would be divided by the product's available-chlorine fraction.
2What is the primary purpose of coagulation in water treatment?
A.To inactivate pathogens before filtration
B.To remove dissolved salts such as sodium, chloride, and sulfate
C.To destabilize colloidal particles so they can aggregate
D.To oxidize taste- and odor-causing compounds
Explanation: Coagulation adds a coagulant such as alum or ferric chloride to neutralize the surface charge of colloidal particles (destabilization), allowing them to aggregate into flocs during flocculation and be removed by sedimentation and filtration. Coagulation does not disinfect, does not remove dissolved salts (that requires membranes or ion exchange), and is not an oxidation step for taste and odor compounds.
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.8,750 mg/L
C.10,000 mg/L
D.12,500 mg/L
Explanation: A solids mass balance around the secondary clarifier (neglecting influent and effluent solids and wasting) gives (Q + Q_RAS) x MLSS = Q_RAS x X_RAS. Solving: X_RAS = (1.0Q + 0.4Q) x 2,500 / 0.4Q = 1.4 x 2,500 / 0.4 = 8,750 mg/L. The 6,250 mg/L value comes from 2,500 / 0.4 (forgetting to add Q_RAS to Q), and 12,500 mg/L is not produced by this balance.
5Which of the following is the most effective method for removing Giardia cysts from drinking water?
A.Free chlorine alone at a typical distribution-system residual
B.Filtration with proper chemical pretreatment
C.UV disinfection alone, without any particle removal
D.Boiling at the point of use by each consumer
Explanation: Giardia cysts require large chlorine CT values, so a normal free-chlorine residual alone is not a reliable barrier. Physically removing cysts requires filtration with proper coagulation/flocculation pretreatment (or membrane filtration), which the Surface Water Treatment Rule credits with log removal. UV and boiling inactivate cysts but do not remove them from the water, and point-of-use boiling is an emergency measure rather than a treatment design.
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 the standard USGS salinity classification, this water would be classified as:
A.Fresh water
B.Slightly saline
C.Moderately saline
D.Highly saline
Explanation: The commonly used USGS salinity classification is: 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; Brine > 35,000 mg/L. At 1,200 mg/L, the water falls in the slightly saline range. (Note: EPA's secondary drinking water standard for TDS is 500 mg/L, a separate aesthetic-based benchmark.)
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 = pi x (40 ft)^2 = 5,027 ft^2. Overflow rate = Flow / Area = 5,000,000 gpd / 5,027 ft^2 = 995 gpd/ft^2. Depth does not enter the overflow-rate calculation. Primary clarifiers ahead of secondary treatment are commonly designed for roughly 800-1,200 gpd/ft^2 at average flow.
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.

Exam sponsor: NCEES (Pearson VUE). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Questions

80 questions

Time Limit

8 hours

Passing Score

Not published by NCEES (scaled, criterion-referenced standard)

Exam / Certification Fees

$400

Exam sponsor website

Reported exam pass rate: 73%. First-time takers 73%, repeat takers 54% (NCEES pass-rate table, July 2026) This describes exam candidates, not OpenExamPrep users or results from using our resources. Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

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

Preparing for the PE Environmental Exam

What You Need to Know

  • Passing score: Not published by NCEES (scaled, criterion-referenced standard)
  • Exam length: 80 questions
  • Time limit: 8 hours
  • Exam / certification fees: $400 Official sources

Using Our Practice Resources

  • Work through all 302 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

PE Environmental: Suggested Study Strategy

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?

NCEES's July 2026 pass-rate table (January-June 2026 examinees) shows 73% for first-time takers and 54% for repeat takers. 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 73% first-time pass rate in NCEES's July 2026 table. 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.