CPWM Waste Treatment Technologies and Disposal Methods 3 — Questions and Answers
Question 1: Which landfill gas component is primarily responsible for its energy recovery value?
- Carbon dioxide
- Nitrogen
- Methane (Correct answer)
- Hydrogen sulfide
Correct answer: Methane
Methane (approximately 50% of landfill gas by volume) is combustible and is the component harvested for energy recovery.
Question 2: Vitrification as a waste treatment method involves:
- Freezing hazardous waste at cryogenic temperatures
- Encapsulating contaminants in a glass-like matrix using high-temperature melting (Correct answer)
- Filtering waste through a glass fiber membrane
- Treating waste with liquid glass coatings
Correct answer: Encapsulating contaminants in a glass-like matrix using high-temperature melting
Vitrification uses extreme heat to melt waste and soil into a stable glass-like solid that immobilizes contaminants.
Question 3: What is 'bioreactor landfill' technology designed to do?
- Prevent any moisture from entering the waste mass
- Accelerate waste decomposition by recirculating leachate and adding moisture to optimize microbial activity (Correct answer)
- Separate recyclables from mixed waste using biological processes
- Use bacteria to neutralize hazardous chemicals before disposal
Correct answer: Accelerate waste decomposition by recirculating leachate and adding moisture to optimize microbial activity
Bioreactor landfills recirculate leachate and add moisture to accelerate biodegradation, increasing gas generation and waste settlement rates.
Question 4: Which of the following best describes 'deep well injection' as a waste disposal method?
- Pumping treated wastewater into shallow aquifers for reuse
- Injecting liquid waste into porous rock formations deep below underground sources of drinking water (Correct answer)
- Installing deep monitoring wells to track waste migration
- Using high-pressure injection to solidify soft waste deposits
Correct answer: Injecting liquid waste into porous rock formations deep below underground sources of drinking water
Deep well injection places liquid waste into geologically isolated porous formations well below any underground drinking water sources.
Question 5: The primary regulatory concern with co-disposal of industrial waste in municipal solid waste landfills is:
- Increased landfill gas production rates
- Potential leaching of toxic substances that could compromise liner systems and groundwater (Correct answer)
- Incompatibility with daily cover soil requirements
- Reduction of available airspace for municipal waste
Correct answer: Potential leaching of toxic substances that could compromise liner systems and groundwater
Co-disposal raises concern that hazardous or toxic industrial waste could leach into and overwhelm the liner system, threatening groundwater.
Question 6: Mechanical biological treatment (MBT) facilities differ from conventional landfills primarily because they:
- Accept only hazardous waste streams
- Pre-treat mixed waste through mechanical separation and biological stabilization before disposal (Correct answer)
- Use only aerobic composting with no mechanical sorting
- Operate exclusively as waste-to-energy facilities
Correct answer: Pre-treat mixed waste through mechanical separation and biological stabilization before disposal
MBT combines mechanical sorting to recover recyclables with biological treatment to stabilize organic fractions before residuals are landfilled.
Question 7: What is the function of a 'daily cover' requirement at a sanitary landfill?
- To increase the heating value of buried waste
- To control vectors, reduce odors, prevent litter, and limit fire risk at the working face (Correct answer)
- To accelerate leachate production for collection
- To aerate the waste mass for faster decomposition
Correct answer: To control vectors, reduce odors, prevent litter, and limit fire risk at the working face
Regulations require daily cover (typically 6 inches of soil or alternative material) to control vectors, odors, litter, and fire hazards.
CPWM Waste Treatment Technologies and Disposal Methods 3
Which landfill gas component is primarily responsible for its energy recovery value?