NCEES Environmental Engineering 5

Question 1

In a biological phosphorus removal system (Enhanced Biological Phosphorus Removal, EBPR), phosphorus uptake occurs in which reactor zone?

Accepted Answer

Aerobic zone — where PAOs take up excess phosphorus

Answer

Phosphorus accumulating organisms (PAOs) release phosphorus under anaerobic conditions and then take up excess luxury phosphorus under aerobic conditions.

Question 2

A 500-acre watershed with a runoff curve number (CN) of 75 receives 3.5 inches of rainfall. Using the NRCS method, what is the potential maximum retention S?

Accepted Answer

3.33 inches

Answer

S = (1000/CN) − 10 = (1000/75) − 10 = 13.33 − 10 = 3.33 inches.

Question 3

A facility emits 50 g/s of a pollutant from a stack. Using a simple Gaussian dispersion model, doubling the wind speed while keeping all else constant will:

Accepted Answer

Halve the ground-level concentration downwind

Answer

In the Gaussian plume model, centerline concentration is inversely proportional to wind speed (C ∝ Q/u), so doubling u halves the concentration.

Question 4

Which unit operation is MOST appropriate for removing dissolved heavy metals (e.g., cadmium, lead) from industrial wastewater before discharge?

Accepted Answer

Chemical precipitation followed by clarification

Answer

Raising pH causes heavy metals to precipitate as hydroxides (e.g., Cd(OH)₂), which are then removed by clarification or filtration.

Question 5

The Toxic Characteristic Leaching Procedure (TCLP) is used to:

Accepted Answer

Simulate leaching of hazardous constituents from waste in a landfill environment

Answer

TCLP uses an acidic extraction fluid to simulate leachate formation in a co-disposal landfill setting and determines if a waste is hazardous by toxicity characteristic.

NCEES Practice Test

NCEES Practice Test

NCEES Environmental Engineering 5