Landfill & Hazardous Chemicals

Question 1

What is the current strategy for reducing waste to landfill?

Answer 1

1) Waste prevention and minimisation
2) Recycle/ Reuse
3) Transformation
4) Landfill

Question 2

What is Landfill?

Answer 2

Landfill

• carefully designed structure built into or on top of the ground in which trash is isolated from the surrounding environment (groundwater, air, rain).
• This isolation is accomplished with a bottom liner and daily covering of soil.
• A sanitary landfill uses a clay liner to isolate the trash from the environment

Question 3

What pollution is caused by Landfill?

Answer 3

1) Leachate
2) Gas Emissions
3) Odour

Question 4

Why is monitoring and managing gases produced in landfill important?

Answer 4

Harmful gases such as methane can escape through surrounding soil.

Question 5

What are the Landfill gas production pattern Phases?

Answer 5

1) Aerobic
Degradeable waste + O2 = CO2 + H20 + biomass + heat
2) Anoxic (Acid Phase)
Degradeable waste = CO2 + H20 + biomass + Organic acids
3) Anaerobic, Methanogenic, Unsteady
CH4
4) Anaerobic, Methanogenic, Steady
CH4

Question 6

How can Methane from Landfill be converted into electricity?

Answer 6

1) Waste disposed in landfill
2) A pipe system collects methane produced by the waste
3) This is transferred to a methane to electricity facility
4) Transmission to electric grid

Question 7

What is the difference between passive and active LFG control measures?

Answer 7

Passive - land fill vents, permeable trenches

Active - Forced gas extraction systems

Question 8

What is Leachate?

Answer 8

Leachate is any liquid that in passing through matter, extracts solutes, suspended solids or any other component of the material through which it has passed.

Question 9

What does a leachate management strategy consist of?

Answer 9

1) Reduction - i.e. reduce the volume of water contacting with waste
2) Containment - collect and store
3) Treatment - Reduce harmful nature
4) Disposal - maintain a safe & cost effective mechanism for disposal of leachate from the site

Question 10

What is the equation for the amount of leachate produced at a landfill site?

Answer 10

LC = PR + SRT – EP – SRO – ST
Where
LC = leachate
PR = precipitation
SRT = surface run to (should be zero for a well designed landfill)
EP = evaporation
SRO = surface run off
ST = change in water storage (changes as a result of chemical decomposition of the waste

Question 11

Why is clay used as a liner?

Answer 11

1) swells when water is added
2) causes exchangeable ions to be held weakly between layers
3) particles are small - low hydraulic conductivity
4) Strong bonds formed across layers

Question 12

What is the future for landfill?

Answer 12

1) Concept of sustainable landfill

2) Landfill mining close to large scale relaisation

Question 13

How do landfill sites treat leachate?

Answer 13

• usually on site treatment due to sensitive sewers
• Reed beds
• nutrients taken by plants - clean enough to discharge
• robust treatment with minimal maintenance

Question 14

What are inorganic and organic hazardous compounds?

Answer 14

Inorganic - heavy metals

Organic - anything with carbon

Question 15

Inorganic contaminant sources

Answer 15

1) Mining / smelting
2) Electronics industry
3) Paints / Pigments
4) Chemical Industry
5) Corrosion
6) Agriculture
7) Forestry
8) Fossil fuel combustion

Question 16

Organic Contaminant soruces

Answer 16

1) Gas works
2) Petrol Spills
3) Disposal of lubricating oils
4) Pesticides

Question 17

What is the bioconcentration factor?

Answer 17

is the concentration of a particular chemical in a tissue per concentration of chemical in water

Question 18

What are:
PAH
Dioxins
PBC
Furans
BTEX
Agent Orange
Organophosphates

Answer 18

Polycyclic Aromatic Hydrocarbons (PAH)
Polychlorinated Biphenyl (PBC)
Benzene, Toulene, Ethyl benzene, Xylenes (BTEX)

They are:
Carcinogenic and mutagenic
Bioacculumate

Question 19

Describe the ways in which liquids can migrate through a geomembrane?

Answer 19

1) Improperly sealed seams
2) Manufacturing defects ( pin holes)
3) Construction and handling defects ( tears, rips e.t.c)

Question 20

Identify the 3 major components of a landfill cover system and describe their functions

Answer 20

1) Vegetative Support
- topsoil material used to support vegetation necessary for proper erosion control, minimising precipitation infiltration and evaporation
2) Filter and Drainage layer
- enhance lateral drainage of any precipitation that infiltrates through the vegetation soil zone
- the filter acts as a separation layer and minimises the migration of materials
3) The barrier layer
- final layer to minimise infiltration through cover system.

Question 21

Final cover over a hazardous waste landfill is typically installed to minimise the environmental risk by addressing potential contaminant pathways. Identify four of the contaminant pathways mitigated through use of a cover system.

Answer 21

1) Direct contact with waste
2) Transport in contaminated precipitation run off
3) Generation of leachate
4) Airborne transport

Question 22

Why do you think a vegetative support layer is typically included in the design of a landfill cover system?

Answer 22

1) it reduces erosion and precipitation
2) Enhances evaportranspiration
- process of returning moisture absorbed by the top soil back to the atmosphere
- reduces infiltration

Question 23

What are the factors which affect the rate of containment migration?

Answer 23

1) Advection
2) Dispersion
3) Hydrolysis
4) Sorption
5) Cosolvation
6) Ionisation
7) Precipitation
8) Biotransformation

Question 24

What are the key features of a landfill site?

and explain what they are for.

Answer 24

1) Bottom liner system
- separates trash and subsequent leachate from groundwater

2) Cells
- where the trash is stored within the landfill

3) Storm water drainage system
- collects rain water that falls on the landfill

4) Leachate collection system - collects water that has percolated through the landfill itself and contains contaminating substances (leachate)
5) Methane collection system - collects methane gas that is formed during the breakdown of trash
6) Covering or cap - seals off the top of the landfill