WAMITAB - Chartered Institution of Wastes Management Landfill Management Operations Questions and Answers — Questions and Answers
Question 1: A landfill site manager observes that leachate levels in a monitoring well have risen above the maximum permitted level specified in the site's environmental permit. What is the most critical immediate operational action to take?
- Record the reading and schedule a review for the next weekly meeting.
- Notify the Environment Agency of a potential permit breach within 24 hours.
- Increase the rate of leachate extraction from the collection system to lower the level. (Correct answer)
- Install additional gas wells to see if there is a related pressure issue.
Correct answer: Increase the rate of leachate extraction from the collection system to lower the level.
The most critical immediate operational action is to mitigate the hazard. Increasing the extraction rate directly addresses the problem of high leachate levels, aiming to bring them back into compliance and prevent uncontrolled release or damage to the liner system. While notifying the Environment Agency is a legal requirement, the first step is always to control the immediate environmental risk.
Question 2: Landfill gas is a natural byproduct of the decomposition of organic waste. Which two gases comprise the vast majority (typically 90-98%) of landfill gas?
- Methane and Carbon Dioxide (Correct answer)
- Hydrogen Sulphide and Ammonia
- Oxygen and Nitrogen
- Carbon Monoxide and Sulphur Dioxide
Correct answer: Methane and Carbon Dioxide
Landfill gas is produced by anaerobic bacteria breaking down organic waste. The primary products of this process are methane (CH4) and carbon dioxide (CO2), which together typically make up 90% to 98% of the gas by volume. The other listed gases are either trace components (like Hydrogen Sulphide) or the main components of air (Oxygen and Nitrogen).
Question 3: According to UK landfill regulations, which of the following waste types is explicitly banned from being accepted at any landfill?
- Asbestos waste in a dedicated cell.
- Contaminated soils meeting hazardous WAC.
- Non-hazardous construction and demolition waste.
- Liquid waste, including wastewater but excluding sludge. (Correct answer)
Correct answer: Liquid waste, including wastewater but excluding sludge.
UK regulations, implementing the Landfill Directive, explicitly ban the disposal of liquid waste in landfills. This is to prevent hydraulic instability and the rapid generation and migration of large volumes of leachate. Specific provisions exist for accepting the other waste types under controlled conditions.
Question 4: An environmental technician detects a sustained, significant increase in methane concentrations at a perimeter monitoring borehole located just outside the engineered containment system. What is this a likely indicator of?
- A recent increase in atmospheric pressure.
- Failure or inefficiency of the landfill gas collection system. (Correct answer)
- A breach in the surface water drainage channel.
- Successful decomposition within the waste mass.
Correct answer: Failure or inefficiency of the landfill gas collection system.
Perimeter monitoring boreholes are designed to detect the lateral migration of landfill gas. A significant and sustained increase in methane outside the containment area indicates that the gas is not being effectively captured by the internal collection system and is escaping. This could be due to blockages, well damage, or insufficient extraction pressure.
Question 5: In the construction of a modern landfill's basal lining system, what is the primary function of a Geosynthetic Clay Liner (GCL)?
- To provide a low-permeability hydraulic barrier to prevent leachate escape. (Correct answer)
- To filter fine particles and prevent clogging of the leachate drainage layer.
- To reinforce the side slopes and ensure geotechnical stability.
- To protect the primary geomembrane liner from being punctured by sharp objects.
Correct answer: To provide a low-permeability hydraulic barrier to prevent leachate escape.
A Geosynthetic Clay Liner (GCL) consists of a thin layer of sodium bentonite clay sandwiched between two geotextiles. When hydrated, the bentonite clay swells to create a highly effective, low-permeability hydraulic barrier, which is its primary function in preventing leachate from migrating into the surrounding soil and groundwater.
Question 6: Which of the following activities is a core legal requirement during the aftercare period of a closed landfill site under an Environmental Permit?
- Excavating and reprocessing the waste for materials recovery.
- Building residential properties on the capped surface.
- Continued monitoring and management of landfill gas and leachate. (Correct answer)
- Ceasing all expenditure on the site to prepare for permit surrender.
Correct answer: Continued monitoring and management of landfill gas and leachate.
The aftercare period begins after a landfill has closed and is no longer accepting waste. It is a legal requirement under the Environmental Permit for the operator to continue managing and monitoring the site to ensure it does not cause pollution. This includes operating and maintaining leachate and gas management systems until the waste mass has stabilized and is no longer considered a risk to the environment.
WAMITAB - Chartered Institution of Wastes Management Landfill Management Operations Questions and Answers
A landfill site manager observes that leachate levels in a monitoring well have risen above the maximum permitted level specified in the site's environmental permit.
What is the most critical immediate operational action to take?