PO Environmental Monitoring & Emissions 2 — Questions and Answers
Question 1: What is the purpose of a vapor recovery unit (VRU) on storage tanks?
- To increase product storage capacity
- To capture hydrocarbon vapors displaced during tank filling and prevent atmospheric VOC emissions (Correct answer)
- To cool the stored product
- To measure tank level more accurately
Correct answer: To capture hydrocarbon vapors displaced during tank filling and prevent atmospheric VOC emissions
A VRU collects hydrocarbon vapors displaced from tank vapor spaces during filling operations, recovering them for use and preventing VOC releases.
Question 2: Under the Clean Water Act, what is a National Pollutant Discharge Elimination System (NPDES) permit?
- A permit to import pollutants for treatment
- An authorization that sets limits on the types and amounts of pollutants a facility may discharge to surface water (Correct answer)
- A stormwater drainage design standard
- A groundwater injection permit
Correct answer: An authorization that sets limits on the types and amounts of pollutants a facility may discharge to surface water
An NPDES permit establishes effluent limits and monitoring requirements for facilities that discharge wastewater or stormwater to US waters.
Question 3: What does opacity mean in the context of stack emissions monitoring?
- The temperature of flue gas at the stack exit
- The degree to which particulate matter in stack emissions blocks light, indicating smoke density (Correct answer)
- The flow velocity of gases leaving the stack
- The pH of condensed stack moisture
Correct answer: The degree to which particulate matter in stack emissions blocks light, indicating smoke density
Opacity is a measure of how much visible particulate smoke is present in stack emissions; high opacity indicates excessive particulate emissions.
Question 4: What is secondary containment required for under SPCC regulations?
- All process piping above 2 inches in diameter
- Oil storage tanks, to capture spills before they reach navigable waters (Correct answer)
- Electrical transformers only
- Compressed gas cylinders
Correct answer: Oil storage tanks, to capture spills before they reach navigable waters
SPCC requires secondary containment (e.g., dikes, berms) around oil storage tanks with sufficient capacity to hold the volume of the largest tank plus precipitation.
Question 5: Volatile Organic Compounds (VOCs) are regulated under the Clean Air Act primarily because they:
- Are directly toxic to aquatic life
- React with NOx in sunlight to form ground-level ozone smog (Correct answer)
- Cause acid rain
- Deplete stratospheric ozone directly
Correct answer: React with NOx in sunlight to form ground-level ozone smog
VOCs react photochemically with nitrogen oxides in the atmosphere to produce ground-level ozone, a major component of smog harmful to human health.
Question 6: What is the role of a wastewater treatment plant (WWTP) in a process facility?
- To generate steam for process heating
- To remove pollutants from process effluent before discharge to meet NPDES permit limits (Correct answer)
- To desalinate cooling water
- To manage solid hazardous waste
Correct answer: To remove pollutants from process effluent before discharge to meet NPDES permit limits
The WWTP treats process wastewater using physical, chemical, and biological methods to reduce pollutant concentrations to permitted discharge levels.
PO Environmental Monitoring & Emissions 2
What is the purpose of a vapor recovery unit (VRU) on storage tanks?