Environmental Engineering Flashcards

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

Answer: Aerobic zone — where PAOs take up excess phosphorus

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

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?

Answer: 3.33 inches

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

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:

Answer: Halve the ground-level concentration downwind

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

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

Answer: Chemical precipitation followed by clarification

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

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

Answer: Simulate leaching of hazardous constituents from waste in a landfill environment

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.

A stormwater detention basin is sized for the 100-year storm event. Its PRIMARY environmental function in an urban watershed is to:

Answer: Attenuate peak discharge rates to pre-development conditions

Detention basins (dry or wet) are designed primarily to reduce peak flow rates, releasing stored runoff slowly after the storm peak has passed.

In the context of Superfund (CERCLA) cleanup, which document presents the analysis of remedial alternatives and recommends a preferred remedy for a contaminated site?

Answer: Feasibility Study (FS)

The Feasibility Study (FS) evaluates and compares remedial alternatives against nine criteria and recommends a preferred remedy prior to the formal ROD.