The Mixed Waste Batch That Was 5.67%, Not 4.5%
Averaging 8% and 1% gave 4.5%, but the two waste streams had different masses. The correct mixed concentration was 5.67% by mass.
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FE EXAM · ENVIRONMENTAL
FE Environmental Practice Questions
Practice FE-style Environmental questions through interactive engineering problems with guided reasoning and detailed solutions.
Interactive problems•Reasoning explained•Solutions included
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PRACTICE SET
Available questions
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QUESTION01
The Mixed Waste Batch That Was 5.67%, Not 4.5%
Averaging 8% and 1% gave 4.5%, but the two waste streams had different masses. The correct mixed concentration was 5.67% by mass.
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QUESTION02
The Incinerator That Achieved 99.9%, Not 99%
An outlet of 0.025 kg/hr from a 25 kg/hr hazardous constituent feed means only 0.1% remains. The destruction/removal efficiency is 99.9%.
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QUESTION03
The Landfill That Produced 12,000 m³ of Leachate, Not 22,000
Precipitation minus evapotranspiration was not enough. Runoff and storage change reduced the annual leachate estimate to 12,000 m³.
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QUESTION04
The Landfill That Lasted 3.42 Years, Not 4.11
Ignoring daily cover made the landfill appear to last 4.11 years. Including 20% cover-volume use reduced the life to about 3.42 years.
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QUESTION05
The Two Collectors That Removed 94%, Not 150%
A 70% cyclone followed by an 80% baghouse did not provide 150% removal. The second device treated only what escaped the first, giving 94% overall removal.
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QUESTION06
The Room That Stabilized at 6.5 mg/m³, Not 0.2
Dividing generation by room volume produced a concentration rise rate. The steady indoor concentration was controlled by ventilation and reached 6.5 mg/m³.
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QUESTION07
The Scrubber That Left 4 lb/hr, Not 36
The scrubber removed 36 lb/hr, but that was not the stack emission. Only 4 lb/hr remained after 90% control.
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QUESTION08
The Contact Tank That Had Only 21 Effective Minutes
The hydraulic detention time was 30 minutes, but baffling reduced the effective contact time to 21 minutes. The CT value was 31.5, not 45.
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QUESTION09
The Clarifier System That Needed 12,000 ft², Not 6,000
Splitting the flow between two clarifiers did not halve the total required area. The system still needed 12,000 ft² in service.
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QUESTION10
The Treatment Plant That Removed 4,379 lb/day, Not 210
The concentration drop was 210 mg/L, but that was not a mass removal rate. At 2.5 MGD, the plant removed about 4,379 lb/day of BOD.
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How do I practice FE Environmental questions?
Choose a topic, solve the problem before seeing the conclusion, and use the final reasoning trail to identify where your original assumption was supported or needed revision. The goal is not only to reach the answer, but to understand the engineering check behind it.