Questions Flashcards
- Describe the role of landfills in the waste management system.
It is the only waste management you cannot be without. The last step in the waste hierarchy, every step brings waste to the landfills. We will always have waste as long as there are humans living. It can be the best alternative to manage residues and detox. It can absorb toxic metals while only releasing salt, carbon and nitrogen (in the best of worlds). It could function as a carbon storage. It represents flexibility and durability in case other waste management do not work as usual.
- What is the alternative to landfilling (in terms of waste disposal)?
Dispersion in form of gas that comes from all the waste management steps.
- The waste hierarchy aims at reducing the number of wastes being landfilled. Name and explain three advantages and disadvantages with this strategy.
+ More reusing, recycling
+ Increased knowledge in waste science
+ Increased environmental control
- More costs (energy etc)
- Requires more transportation
- Increased time due to sorting and administration
- What are the three landfill classes from a legal point of view, how do the landfills differ and why are different materials destined to different facilities?
Hazardous waste – can cause big problems for the environment, therefore there are higher restrictions for the landfill of hazardous waste, for example regarding the permeability of the bottom layer. Double liner system. More control measures
Non-hazardous waste – municipal waste.
Inert waste - Waste that does not undergo significant physical, chemical, or biological transformation. Waste will not dissolve, burn, biodegrade, or react. No liners needed. No gas collection system.
Different materials are destined to different facilities due to the higher costs of hazardous waste landfills.
The classes of the landfills are dependent on the leachability of toxic elements in the waste.
- Which purposes do landfills serve in waste management?
Storage – temperate or permanent
Waste treatment and recycling processes
Back up for other processes.
- There are different goals for the characterization of waste. What is the general goal for waste characterization? Name and explain three goals from the perspective of a landfill operator.
- Risk assessment: there is a need to know what the environmental risks of the waste are.
- Legal requirements: how the waste can be handled according to law. Non-hazardous, hazardous vs inert.
- Technology development: how the waste can be treated
- Economical: how to make a profit out of the waste
- What kind of knowledge of the waste is required to accept waste at landfills (that is what kind of information must be included in the waste characterization documents)?
- Identity of waste producer
- The process the waste comes from
- Data of composition of waste and the leaching behaviour.
- Appearance of the waste (smell, colour, physical form)
- Waste code according to European list of waste
- The landfill class.
- Comment on why it cannot be recycled.
- Why is waste characterization important in landfill technology?
It gives information necessary to manage waste in a suitable way, about its environmental risks. You get a simplified description of the real waste behaviour, which can then be used to choose appropriate treating methods and technical solutions. It shows the future environmental impact of the chosen management strategy.
- What factors affect the leaching of contaminants?
Physical factors: Particle properties, internal pore structure, temperature, time of contact, L/S ratio
Chemical factors: pH, redox, availability of complex formers, availability of sorption surfaces
External factors: Precipitation, temperature, wind
Landfill technology: Landfill and barrier design, filling technique (compacting etc), process technique (leachate circulation etc)
- The L/S ratio is the liquid to solid ratio a waste has been exposed to. Estimated in-situ L/S ratios can be used to develop bench-scale leaching tests for simulating landfill leaching processes over time. Sometimes the L/S is translated into a time scale by the use of infiltration rates and leaching predictions are made. Explain why there is a risk for such leaching tests giving misleading results and give examples for over/underestimations of concentrations and/or time frames. Take into account your knowledge about (a) the factors controlling leaching as well as (b) in-situ waste conversion processes.
Leaching tests are often simplified, done over a short period of time whereas in situ the process takes decades. It is mainly performed in room temperature when in situ has big variations in conditions. It is also difficult to control biology (microbial activity) and redox in the lab. Conditions change over time in a landfill – which is not shown in a leaching test. Conversion of L/S ratio to time can be done for salts.
Precipitation of metals in landfills – not in lab.
- Why is landfill siting a process that often takes decades to complete?
Many field investigations have to be done which can take a long time, such as geographical, geological and geophysical. Physical planning has to be done to make sure its accessible and has no conflicting interests. The public has to be involved and it has to be legally approved. These procedures can take a long time.
- What are the principal aspects to consider in a landfill siting process? Give one example for each category.
The need – waste level: for example the quality of the waste.
The impact – ecological level: for example the end use alternatives.
The interests – social level: for example conflicting land use such as agriculture or airports.
- Describe important steps of the procedure for landfill siting. Which step takes usually most time and why?
Establish goals for the landfill and identify facility design and need. What kind of waste should be landfilled and in what quantity.
First identify potential sites where it can be based on for example hydrogeological aspects.
Then, selection and evaluation must be done on detail level. Final selection is done and then acquisition and legal approval of the site.
The planning stage of a new landfill takes the longest time.
- When siting a new landfill in Sweden, there is a legal requirement to invite and listen to the public in the planning process. Discuss how, in practice, the consultation of the public can be done. What purposes should such consultation serve?
To build a relationship with the public. To give information to the public and to hear their complaints. To learn more about the area from the locals. Having a “samråd” with legal requirements according to MKB, not all countries do this.
The purpose is to see that the public understands the proposal and the purpose. That their opinions will be heard.
- Describe how one could integrate landfills with natural retention and adsorption systems.
By using a natural slope and swamp, and placing the landfill on top of the hill. Leachates from the landfill can flow through unsaturated zones and there get delayed or partly decomposed. Then, in the saturated zone the leachate gets diluted. Finally the leachate can flow out in natural swamps, a reduced environment, which immobilizes metals further. Immobilisation in sediments detoxifies the system.
