AQS Remediation & Mitigation Strategies 3 — Questions and Answers
Question 1: Which emission control technology is most effective for removing fine particulate matter (PM2.5) from industrial exhaust streams?
- Cyclone separator
- Electrostatic precipitator (ESP) (Correct answer)
- Gravity settling chamber
- Simple expansion chamber
Correct answer: Electrostatic precipitator (ESP)
Electrostatic precipitators use electrical charges to capture PM2.5 and smaller particles with efficiencies exceeding 99%.
Question 2: A facility implements a leak detection and repair (LDAR) program primarily to control emissions of:
- Criteria pollutants from combustion stacks
- Fugitive VOC emissions from valves, flanges, and connectors (Correct answer)
- Particulate matter from material handling
- NOx from burner operations
Correct answer: Fugitive VOC emissions from valves, flanges, and connectors
LDAR programs specifically target fugitive VOC emissions from equipment components such as valves, pump seals, and pipe flanges.
Question 3: In phytoremediation, the process by which plants absorb, translocate, and concentrate contaminants in aboveground biomass is called:
- Rhizofiltration
- Phytostabilization
- Phytoextraction (Correct answer)
- Phytodegradation
Correct answer: Phytoextraction
Phytoextraction involves uptake of metals or organics into plant tissue, which is then harvested to remove contaminants from the site.
Question 4: Selective catalytic reduction (SCR) systems used to control NOx emissions require which input chemical?
- Activated carbon
- Urea or anhydrous ammonia (Correct answer)
- Calcium hydroxide slurry
- Sulfuric acid
Correct answer: Urea or anhydrous ammonia
SCR systems inject urea or ammonia as a reductant; over a catalyst, it reacts with NOx to produce harmless N₂ and H₂O.
Question 5: Which condition would most likely cause a thermal oxidizer to fail to meet its destruction and removal efficiency (DRE) permit limit?
- Excessive retention time at design temperature
- Combustion chamber temperature falling below design setpoint (Correct answer)
- High air-to-fuel ratio above stoichiometric requirements
- Increased stack height above the permitted value
Correct answer: Combustion chamber temperature falling below design setpoint
DRE depends on the three Ts (temperature, time, turbulence); insufficient temperature is the most common cause of incomplete destruction.
Question 6: At a Superfund site, an institutional control such as a deed restriction is classified as which type of remediation component?
- Active treatment technology
- Engineering control
- Long-term monitoring requirement
- Non-engineered administrative control (Correct answer)
Correct answer: Non-engineered administrative control
Deed restrictions and other legal instruments are administrative (institutional) controls that limit site use without physical containment.
Question 7: Multi-phase extraction (MPE) is advantageous over standard SVE at sites where:
- Contamination is confined entirely to the vadose zone
- Low-permeability soils trap both NAPL and dissolved phase near the water table (Correct answer)
- Only volatile compounds are present with no residual liquid
- Groundwater is not impacted by contamination
Correct answer: Low-permeability soils trap both NAPL and dissolved phase near the water table
MPE simultaneously extracts soil vapor, groundwater, and NAPL using high vacuum, making it effective in low-permeability smear zones.
AQS Remediation & Mitigation Strategies 3
Which emission control technology is most effective for removing fine particulate matter (PM2.5) from industrial exhaust streams?