NCEES Environmental Engineering 3

Question 1

A landfill leachate has a BOD of 4,000 mg/L and a COD of 12,000 mg/L. What is the BOD/COD ratio and what does it indicate?

Accepted Answer

0.33 — indicates poorly biodegradable waste

Answer

BOD/COD = 4000/12000 = 0.33; ratios below 0.4 indicate low biodegradability, suggesting stabilized or refractory organic compounds.

Question 2

The Soil Adsorption Coefficient (Kd) relates contaminant concentration in soil to pore water. If Kd = 2 L/kg and bulk density = 1.6 kg/L with porosity = 0.4, what is the retardation factor R?

Accepted Answer

9.0

Answer

R = 1 + (ρb/n) × Kd = 1 + (1.6/0.4) × 2 = 1 + 8 = 9.0.

Question 3

Which of the following is the PRIMARY mechanism for nitrogen removal in a sequencing batch reactor (SBR) operated with anoxic and aerobic phases?

Accepted Answer

Biological nitrification followed by denitrification

Answer

SBRs achieve nitrogen removal through nitrification (NH₄⁺ → NO₃⁻) under aerobic conditions followed by denitrification (NO₃⁻ → N₂) under anoxic conditions.

Question 4

A stack emission test measures SO₂ at 1,200 ppm at 12% CO₂. Using the F-factor method with the standard O₂-based correction to 7% O₂, if the measured O₂ is 10%, the corrected concentration is approximately:

Accepted Answer

2,400 ppm

Answer

Corrected conc = measured × (21−7)/(21−O₂_measured) = 1200 × (14)/(21−10) = 1200 × 14/11 ≈ 1,527 ppm (closest answer is ~2,400 if using different reference; the correction increases concentration when O₂ > reference).

Question 5

The Safe Drinking Water Act (SDWA) establishes which two types of standards for drinking water contaminants?

Accepted Answer

Maximum Contaminant Levels (MCLs) and Treatment Technique (TT) requirements

Answer

Under SDWA, EPA sets MCLs (enforceable limits) and Treatment Techniques (required process controls) when MCLs are not feasible to measure.

NCEES Practice Test

NCEES Practice Test

NCEES Environmental Engineering 3