Landfill

Landfill
An engineered method for disposing refuse/waste by spreading the waste in thin layers, reducing each layer to the smallest practicable volume and periodically applying and compacting a layer of soil to cover the waste

Landfilling process
Deposition of solid waste in a prepared section of the site
Spreading and compaction of waste in layers (30-60 cm)
Covering waste with a layer of cover soil at the end of each day’s work (minimum 15 cm)
Finally cover the entire construction with a compacted earth layer (minimum 60 cm)

Landfill techniques
Trench method

Narrow excavation
Soil removed and stockpiled
Waste deposited at one slopped end
waste spread on an inclination of 3 horizontal : 1 vertical spread and compacted
Covered with soil at the end of each day
When entire trench filled, final earth cover is placed

Suitability
Flat areas
Groundwater is at significant depth
Cover soil is available

Area method
Waste is placed on undisturbed existing ground surface
Only top soil is removed for final cover

Suitability
Rough and irregular areas
Groundwater water table is near the surface

Ramp method
Combines both trench and area methods
Before deposition, small excavation in front of the proposed face of an existing slope
Soil removed and stockpiled
Waste deposited onto slope

Suitability
Irregular terrain of moderate sloping

Landfill site selection
Siting criteria

Economic

Relate to the cost of obtaining, developing and operating a site to an acceptable standard

Cost of land – land area 10-20 years
Development cost – surface drainage
Cover material availability
Access roads
Hauling distance
Value of land
Regional waste disposal links


Environmental

Relate to the potential threat to the physical environment, specifically to water resources

Groundwater vulnerability
Permeability of soils
Landuse
Topography - Slope (gentle is best)
Geology

Social

Relate to the possible adverse impact of a landfill on quality of life and to potential public resistance

Distance form settlement
Prevailing wind direction
Public acceptability
Sites of cultural value
Visibility
Proximity to airports


Advantages

Cheap initial costs
Cheap operational costs
Flexible
Easy putting into operation
Reclamation of land


Disadvantages

Cover soil
Pollution problem
Public acceptance


Environmental pollution

Leachate

In a landfill that is deprived of oxygen, waste materials may liquefy into an acid water solution called leachate
This leachate dissolve toxic components in landfill solids as it flows down through the landfill and out the bottom
Groundwater pollution

Gases

50% CH4 and 45% CO2
Peak production – 2 years
Gases vented into atmosphere
Greenhouse effect – global warming
CO2 is heavier – settle at the ground making water acidic

Prevention/minimization of environmental
pollution

Prevention of leachate

Prevent surface runoff over the landfill
Use good cover material – impermeable
Raise landfill above surrounding ground
Lining bottom of landfill with synthetic (impermeable) plastic or clay material

Gases
Install gas collection
Convert methane into electricity


Odors, flies and rodents
Use good cover material

Dust
Sprinkle water on access road and within landfill

Paper and plastics
Planting trees around landfill



Classification of Landfill Sites
Landfill are classified according to

Waste types

Inert waste
Less than 5% of biodegradable organic components

General waste
All waste that is not inert, wet or hazardous

Wet waste
Waste with a high moisture content

Hazardous waste
Waste that has the potential to have a significant adverse impact on the public or environment

Landfill size

Rural
< 500 tons p.a (up to
2,000 people)

Small
500 – 6,500 tons p.a (up to 26,500 people)

Medium
6,500 – 65,000 tons p.a

Large
>65,000 tons p.a


Classification of

Inert waste landfill
General waste landfills
Wet/Hazardous waste landfills