Landfills: An Overview

Landfills: An Overview

David T. BrownDept. of Tourism and EnvironmentBrock UniversitySt. Catharines, Ontario L2S 3A1

References: O’Leary, Philip & Patrick Walsh. Landfill Course. Waste Age, January 2002 – January 2003.

TREN 3P14: Sustainable Integrated Waste Management

http://landfill-ed.wasteage.com/

Landfill

• conceived in the 1960s as a planned method of solid waste disposal

• prior to that, municipal solid waste disposed of in organized or unorganized open dumps.

• waste may not have been covered• likely was burned as part of the disposal• practice

Landfill

1970s – North America and Europe:

• initiatives made to improve solid waste disposal practices

Sanitary Landfill

• an engineered facility for the disposal of municipal solid waste (MSW) designed and operated to minimize public health and environmental impacts

Photo: www.gin.hr/ project_jak.htm

http://www.gin.hr/project_jak.htm




Sanitary Landfill

• typical landfill consists of several cells in which the waste is systematically placed

• Landfill base usually consists of a liner (clay or synthetic) that minimizes the leakage of liquid waste materials and leachate into groundwater system

Installation of synthetic landfill liner






First cell of landfill (area method)

Accessramp

Refuse

Photo: David T. Brown

Sanitary Landfill

• Waste built up in layers and compacted

• Wastes covered daily with soil, geomembranes, or other cover materials to prevent lightweight wastes, dust, and odors from escaping and to discourage vermin

Photo: Bung-orn Thirapoj

Weigh Station


Weigh Scale operator


Truck on weigh scale at entry

Load cell to weigh truckPhoto: David T. Brown


Landfill liner detail

Synthetic linerPhoto: David T. Brown

Sanitary Landfill

• Modern landfills are sophisticated facilities that require millions of dollars to build

• Services provided often valued at millions of dollars per year

Sanitary Landfill

• Typical landfill operates between 10 and 20 years

• During this period, waste in the landfill undergoes complicated decomposition processes

Sanitary Landfill

• Decomposition results in the release of:– liquids (leachate)

must be contained in the landfill and treated prior to release

– gases must be managed as they escape through the landfill cover, or are collected for burning or storage

Lined landfill section

Liner

Ponded water

Sand cover to protect and retain plastic liner


Leachate retention pond

Culvert


Access well in new section

Liner

Access well


Sanitary Landfill

Various options available to landfill operators regarding:

• Preparation of waste before it arrives at the landfill

• Compaction procedures for waste

• Alternatives for managing leachate and gas

Technological innovations

Recent technological innovations include:• improved groundwater monitoring and leachate

collection systems• Improved gas monitoring and collection systems

– meet air pollution control standards– facilitate energy recovery

• installation of geosynthetic covers • introduction of large waste compaction equipment• Development of alternative cover materials installed

during final closure

Leachate collection conduits






Bioreactor landfills

• Landfill is operated as a managed treatment facility

• Natural decomposition process accelerated to– reduce waste volume – increase the amount of waste that can be landfilled

• Bioreactors expected to reduce long-term emissions into the groundwater or the atmosphere.

• Several bioreactor landfills being operated on a limited basis in the United States and in Western Europe.

The Life of a Landfill

Phase 1: Site Selection and Investigation

• sites evaluated from geotechnical and environmental standpoints

• initiation of a public participation program, to openly communicate with the public and minimize potential landfill opposition


Phase 2: Design and Regulatory Approval

• detailed plans and specifications for facility are prepared

• regulatory approvals are obtained

• financial commitments are received

• construction is initiated


Phase 3: Site Construction• development of support facilities• development of the landfill’s first one or two

cells

Phase 4: Operation• landfill opened and operated over a period

of years• additional cells constructed as needed


Phase 5: Site Closure• When cells are filled to capacity they are

closed and monitored• Final closure often involves site remediation

Phase 6: Long-Term Care• Monitoring for 30 years after closure• Owner / operator responsible for remedial

action and facility maintenance

Environmental Considerations

Groundwater Quality

• If landfill not properly lined, waste can escape into groundwater

• Most landfills constructed with a combination of low-permeability compacted soil and geomembranes

Ref: O’Leary, Philip & Patrick Walsh. 2002. Land Disposal of MSW: Protecting Health & Environment. Waste Age- February 2002, pp. 38-43.



Wetland and Stream Protection

• Surface runoff detrimental to adjacent wetlands and streams

• Chemical, organic, and sediment contamination are all problematic

• May be reduced or eliminated with proper design and management





Air Quality

• Odours

• Gaseous emissions:

– direct from the waste (volatile solvents, fumes, odours)

– from anaerobic decomposition (e.g., methane)


Air Quality

• Blowing grit, dust, lightweight litter

• Combustion gases, smoke, and particulates, if landfill catches fire



Greenhouse Gases

• Landfills emit significant quantities of methane and carbon dioxide

• Control mechanisms are being mandated at the provincial level (Canada) and national levels (USA)

Landfill gas combustion stackLandfill gas

liquification facility


Safety Considerations

Explosion Potential

• Landfill gas is a potentially explosive combination of methane and carbon dioxide

• Explosive landfill gas may migrate underground into buildings, or collect in explosive pockets onsite


Slope Stability

• landfills have become larger; heights have significantly increased => leads to slope stability concerns

• Steep slopes canfail, with catastrophic results.













Slope Stability• earthquake activity can also potentially

cause slope failure at a large landfill• also an issue at landfills that receive

specialized wastee.g. if wastes contain significant amounts of water, slope stability decreases


Worker SafetyMaterials in landfills may be hazardous.

Workers need protection from:

• Sharp, hazardous, infectious or pathogenic wastes• Dust and particulates• Noise and hazards from vehicles and equipment• Fire and explosion• Vermin• Volatile substances, odours• Extreme weather, wind, high and low temperatures• Construction accidents


Decomposition in landfills

• The decomposition process is a principal driving force in the development, operation and closure of a landfill

• MSW contains organic material that naturally decomposes when landfilled

Decomposition in landfills

Two phases:

• Aerobic (oxygen present)

• Anaerobic (stages 1 and 2) (little or no oxygen present)


Organic refuse



Decomposition in landfillsBoth aerobic and anaerobic phases have byproducts:

Aerobic phase: • carbon dioxide • contaminated water that flows toward the base of

the landfill

Anaerobic phase: • methane • carbon dioxide• liquid byproducts with various contaminants

• decomposition process continues for many years

• trace quantities of materials which may impact the environment are contained in both landfill gas and leachate (e.g., metals in leachate; VOCs, greenhouse gases)

• trace materials are generated until the landfill becomes completely stabilized (between 300 and 1,000 years)

















Documents

Landfills: An Overview