10 exam-style questions with answers and explanations, straight from our 1,030-question bank. Tap an answer to check yourself. When you're ready, take the scored version in the free practice test.
The PE-Env exam has 80 questions and runs 8 hours.
These 10 free PE-Env questions are organized by exam domain, so you can see how each part of the Principles and Practice of Engineering - Environmental blueprint is tested. Reveal the answer and explanation under each question.
Domain 1: Water
Question 1
A municipal activated-sludge plant begins discharging elevated ammonia after the influent alkalinity declines. The aeration-basin temperature remains 20°C, solids retention time remains 20 days, and dissolved oxygen is consistently 3.0 mg/L throughout the basin. Basin pH has fallen from 7.3 to 6.1, with only 12 mg/L residual alkalinity as CaCO3. No toxic discharge or solids loss is detected. Which operating adjustment addresses the limitation indicated by these findings?
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Correct answer: B - Add alkalinity under controlled dosing to restore a suitable pH for nitrification.
Question 2
At peak hourly flow, a drinking-water plant sends 1,500 U.S. gal/min through a clearwell containing 180,000 U.S. gal. Tracer testing establishes T10/(V/Q) = 0.40. The applied chlorine dose is 2.5 mg/L, and the minimum clearwell-outlet free-chlorine residual under these conditions is 1.1 mg/L. For the measured pH, temperature, and remaining inactivation credit, the applicable minimum CT is 60 mg·min/L. The disinfection design check should report:
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Correct answer: A - 52.8 mg·min/L; the required CT is not achieved.
Question 3
Which alum dose should advance to confirmatory pilot testing? A surface-water plant requires filtered turbidity no greater than 0.20 NTU and dissolved aluminum no greater than 0.10 mg/L. Jar tests use identical raw water, pH, mixing, settling, and bench-filtration conditions. Results are: 15 mg/L alum → 0.40 NTU and 0.02 mg/L dissolved aluminum; 25 mg/L → 0.12 NTU and 0.04 mg/L; 40 mg/L → 0.10 NTU and 0.14 mg/L; 60 mg/L → 0.08 NTU and 0.21 mg/L.
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Correct answer: B - 25 mg/L alum.
Domain 2: Solid and Hazardous Waste
Question 4
Incinerator ash is derived from a spent solvent correctly designated F002 listed hazardous waste. Representative testing shows that the ash exhibits none of the four hazardous-waste characteristics. No delisting or other exclusion applies. Under federal RCRA requirements, the ash is:
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Correct answer: C - Listed hazardous waste, because the applicable listing persists in the treatment residue.
Question 5
Leachate head in an upstream portion of a municipal solid-waste landfill cell has risen to 45 cm above the liner. At the collection sump, however, the liquid level remains low, near the pump's normal shutoff elevation. A pump test confirms the specified discharge capacity and an unobstructed force main. Rainfall and waste-placement rates have not changed. Which fault best reconciles the high upstream head with the low sump level?
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Correct answer: B - Restricted flow through the drainage layer or collection piping leading to the sump.
Domain 3: Sustainability
Question 6
Both pumps at a lift station stop during a flood even though either can carry the entire design flow. The pumps and adequately sized, fueled generator are undamaged; the shared cabinet containing the switchgear and controls is flooded. Which investment addresses the failure shared by both pumps?
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Correct answer: B - Elevate and flood-protect the shared switchgear and controls.
Domain 4: Air
Question 7
A coating line generates 200 kg/day of a volatile organic compound. Its enclosure captures 75% of that mass and sends it to a thermal oxidizer with a verified destruction efficiency of 96%. Uncaptured vapor leaves the building untreated. The permit limits the combined stack and fugitive emissions of this compound to 40 kg/day. During a day with no bypass or equipment downtime, which emissions entry is correct?
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Correct answer: D - 56 kg/day; exceeds the limit.
Domain 5: Site Assessment and Remediation
Question 8
Dissolved nickel results from a former plating site arrive with the following quality-control data: method blank, not detected; laboratory control sample recovery, 101% against an 80-120% acceptance range; sample matrix-spike recovery, 38% against a 75-125% range; and laboratory duplicate relative percent difference, 6% against a 20% maximum. Calibration checks pass, and the spike addition was large enough that native nickel did not obscure recovery. What concern should govern validation of this sample's nickel result?
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Correct answer: A - Matrix-specific interference may be biasing the nickel result low.
Question 9
Following electron-donor injection into a chlorinated-solvent plume, monitoring wells show declining tetrachloroethylene (PCE) and trichloroethylene (TCE) under strongly reducing conditions. The program measures the parent solvents, pH, dissolved oxygen, and groundwater levels, but not chlorinated breakdown products. Before crediting the decline as successful detoxification, which analytical addition most directly tests whether dechlorination has stalled at hazardous intermediates?
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Correct answer: C - cis-1,2-Dichloroethene, vinyl chloride, and ethene.
Domain 6: Environmental and Occupational Health
Question 10
During a permitted entry into a valve vault, an alert worker's continuous atmospheric monitor alarms at 16.8% oxygen. Combustible gas remains at 0% of the lower explosive limit. The monitor passed its pre-use checks, and the worker can exit without assistance but asks for two more minutes to finish tightening a connection. What instruction must the attendant give now?
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Correct answer: D - Exit immediately; further entry must wait until acceptable conditions are restored.
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