CPWM Waste Treatment Technologies and Disposal Methods 2 — Questions and Answers
Question 1: What is the primary purpose of a leachate collection system in a sanitary landfill?
- To aerate the waste mass
- To capture liquid that percolates through waste and prevent groundwater contamination (Correct answer)
- To generate biogas for energy recovery
- To compact waste layers more efficiently
Correct answer: To capture liquid that percolates through waste and prevent groundwater contamination
Leachate collection systems capture contaminated liquid that migrates through the waste mass to protect underlying groundwater.
Question 2: Which thermal treatment technology uses oxygen-deficient high-temperature conditions to convert waste into syngas?
- Incineration
- Pyrolysis
- Gasification (Correct answer)
- Plasma arc treatment
Correct answer: Gasification
Gasification converts carbonaceous waste into syngas (carbon monoxide and hydrogen) under high temperatures with limited oxygen.
Question 3: Aerobic composting differs from anaerobic digestion primarily in that aerobic composting:
- Produces methane as a primary output
- Requires the presence of oxygen throughout the process (Correct answer)
- Occurs only in sealed reactors
- Generates more leachate than anaerobic digestion
Correct answer: Requires the presence of oxygen throughout the process
Aerobic composting requires oxygen to support microbial decomposition, while anaerobic digestion occurs without oxygen.
Question 4: A Subtitle D landfill in the US must have a composite liner system consisting of:
- Two HDPE geomembranes with no soil component
- A geomembrane over two feet of compacted clay with hydraulic conductivity ≤1×10⁻⁷ cm/s (Correct answer)
- Only compacted native soil at least 5 feet thick
- Bentonite panels without geomembrane overlay
Correct answer: A geomembrane over two feet of compacted clay with hydraulic conductivity ≤1×10⁻⁷ cm/s
EPA Subtitle D requires a composite liner of an HDPE geomembrane directly overlying at least two feet of compacted soil with hydraulic conductivity no greater than 1×10⁻⁷ cm/s.
Question 5: Which waste treatment method is most appropriate for treating highly concentrated organic liquid hazardous waste?
- Solidification/stabilization
- High-temperature incineration (Correct answer)
- Aerobic land farming
- Dilution and surface discharge
Correct answer: High-temperature incineration
High-temperature incineration destroys organic hazardous compounds through thermal oxidation and is the preferred method for concentrated organic liquid hazardous wastes.
Question 6: What is the main environmental concern associated with open burning of municipal solid waste?
- Excessive noise pollution
- Emission of dioxins, furans, and particulate matter into the atmosphere (Correct answer)
- Overproduction of leachate
- Rapid depletion of groundwater resources
Correct answer: Emission of dioxins, furans, and particulate matter into the atmosphere
Open burning releases toxic dioxins, furans, heavy metals, and fine particulates, making it a significant air quality and public health hazard.
Question 7: In a waste-to-energy (WTE) facility, the role of the air pollution control (APC) system is to:
- Increase the heating value of incoming waste
- Remove pollutants such as acid gases, dioxins, and particulates from flue gas before atmospheric release (Correct answer)
- Generate additional electricity from exhaust heat
- Condense water vapor to recover leachate
Correct answer: Remove pollutants such as acid gases, dioxins, and particulates from flue gas before atmospheric release
The APC system in a WTE facility treats combustion gases to remove regulated pollutants before stack discharge.
CPWM Waste Treatment Technologies and Disposal Methods 2
What is the primary purpose of a leachate collection system in a sanitary landfill?