Bonusfrågor från Examination questions and example answers Flashcards
Define the word “waste” from a legal point of view. Define the word “landfill” from a legal point of view.
Waste definition: everything included in a waste category according to the ordinance about waste, and which the owner intend to get rid of or is obliged to get rid of
Landfill definition: a place where you keep waste for more than 3 years
Name two realistic drivers for landfill mining and explain them briefly.
- Recover landfill space to landfill more (capacity extension)
- Reclamation of the land for other use
- Remove hazardous waste or an old landfill from an unsuitable place.
How will a biological treatment of biological degradable wastre before landfilling affect the leachate quality?
Lower concentrations of organic matter, nutrients in the leachate, direct start in the methanogenic phase after landfilling, see methanogenic conditions above.
How will leachate recycling (pumping back to the landfill) affect the leachate quality?
Intensification of whatever process is occurring in the waste (since all processes involves water), homogenization of processes over the landfill body, including humidity, salt concentration and temperature. All these factors can influence leachate quality differently depending on conditions. E.g. a cold temperature may slow down degradation and promote a different ecology than warm water.
Name three important factors that affect the composition of landfill leachate (content and concentration) and describe the influence of each factor.
- Waste type and composition
- Landfill environment
- Landfill operation/management
- Landfill age and leaching ratio
- Sampling
Describe!
What is the purpose of a LFG flare?
To decrease the greenhouse emissions from a landfill by oxidising CH4 into CO2
Why is the heat release from biological oxisation of methane lower than from combustion (chemical oxidation) of methane? How much lower is it theoretically?
Because some of the substrate goes into new cells (and hence, is not oxidised). 40% lower.
How can one assess the remaining gas formation potential of an old landfill? Describe briefly two in principle different methods.
- Look at the documentation – what has been landfilled? And then based on the waste composition (+ age of the landfill, + gas produced so far) assess the remaining potential
- Take samples and measure the BMP or the COD
- Perform emission measurements and compare parts of the landfill with different age.
What is landfill gas?
A mix of biogas, water vapour, air and fumes that have evaporated from material in the landfill.
Why is water essential for the degradation or organic material?
Because all biological reactions occur in water solution
How can you improve the capture of landfill gas without incresing the suction (negative pressure) in the collection system (and thus increase the risk of sucking air into the landfill)?
You increase the surface of the gas collectors
Why is COD higher than BOD7?
Because chemical oxidation also affects organic matter that is not or hardly biodegradable
Composting ca be used as a pre-treatment of highly degradable organic matter before landfilling. What is the main advantage of pre-composting? Explain why it has this positive effect. How will it influence the total gas production in the landfill?
Degrading easily degradable organic matter and so avoiding the formation of too much organic acids during the acidogenic phase, or even (preferably) completely avoiding the acidogenic phase. The total gas production often increases as less organic matter is discharged with the leachate.
