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Waste Management > 6. Waste Options: Landfills > Flashcards

6. Waste Options: Landfills Flashcards

1
Q

Landfill definition

A

-waste management facility at which waste is disposed of by placing it on or in land

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2
Q

Land fills don’t include

A
  • surface impound
  • land treatment facility
  • salt cavern
  • disposal well
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3
Q

Dump

A

Place for the disposal of domestic waste

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4
Q

Sanitary Landfill

A
  • Place for the disposal of refuse and other waste materials by burying it and covering it with soil
  • engineer designed
  • waste gets compacted
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5
Q

Alberta Landfill Regulatory bodies

A
  • AEPEA

- WCR: States no hazardous waste will be disposed of in a landfill (except Class I can take hazardous solids)

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6
Q

Standards for Landfills in Alberta

A

-provide minimum requirements for the development, operation, monitoring, closure and post closure of landfills

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7
Q

Standards of Landfills applies to

A
  • Disposal activities at new land fills
  • New cell at existing landfills
  • Lateral extensions at existing landfills
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8
Q

Purpose of Standards for Landfills

A

Provide assurance to the public regarding

  • protection of ground water and surface water
  • management of nuisances associated with landfills
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9
Q

Environmental Code of Practice for Landfills in Alberta

A

-Provides the minimum requirements for the construction, operation, and reclamation of landfills that accept < 10 000 tonnes of non-hazardous and inert waste per year

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10
Q

3 Types of Landfill Groups

A
  • Municipal
  • Industrial
  • Oilfield
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11
Q

Municipal Landfill Classes

A
  • Modified Sanitary Landfill
  • Regional Sanitary Landfill
  • Dry Waste Site
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12
Q

Modified Sanitary Landfill

A
  • services <10,000 people

- municipal solid waste

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13
Q

Regional Sanitary Landfill

A
  • services >10,000 people
  • municipal solid waste
  • generally in urban areas
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14
Q

Dry Waste site

A
  • can’t be used for normal household waste

- takes demolition material

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15
Q

Industrial Landfill classes

A

Class I
Class II
Class III

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16
Q

Class I Industrial Landfill

A

-highest risk because accepts both solid and liquid hazardous waste except waste specifically excluded
-only landfill that accepts HW
=

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17
Q

Class II industrial landfills

A
  • most common industrial landfill
  • no HW
  • high to medium risk
  • can accept asbestos, paper mill waste, waste water treatment sludges, WH contaminated soils
  • equivalent to municipal sanitary landfill
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18
Q

Class III Industrial Landfills

A
  • inert
  • low risk
  • no HW
  • no decomposable waste
  • no liquids
  • equivalent to municipal day landfill
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19
Q

Oilfield Landfill classes

A
  • Class 1a
  • Class 1b
  • Class II
  • Class III
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20
Q

Oilfield Class 1a

A
  • accepts solid oil field waste (hazardous and non hazardous)
  • have 2 liners of which at least 1 is a geosynthetic liner
  • leak detection systems between the barriers
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21
Q

Oilfield Landfil class 1b

A
  • accepts solid oil field waste (both hazardous and non hazardous)
  • has 1 liner (either geosynthetic or compacted day liner)
  • leachate detection system
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22
Q

Oilfield waste class II

A
  • accepts only nonhazardous solid oil field waste
  • has one liner
  • has a leachate collection system
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23
Q

Oilfield Landfill class III

A
  • accepts only nonhazardous, inert and non leachable solid oil field waste
  • inert waste
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24
Q

3 major issues with Landfill siting

A
  • Political/Social
  • Economic
  • Environmental/Technical
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25
Q

Political/Social issues with Landfill Siting

A
  • NIMBY
  • consider future use: golf course, parkland, recreational park
  • must make process transparent and involve community from start
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26
Q

Economic issue with landfill siting

A
  • Site Capacity (Volume)
    • want 25+ years operational life
  • Accessibility
    • don’t want too long transport distances –> $
    • don’t want in residential areas
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27
Q

Environmental/Technical concerns with landfill citing

A
  • landfill shouldnt be in contact with surface or ground water
  • must consider geology
    • can’t put in a ravine, gully or coulee
    • not located w/in 300m natural areas that permanently contain water
    • not w/in 300m of manmade surface features that permanently contain water
  • underlying soil and rock types (want to avoid high permeability areas
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28
Q

Potential Problems with landfills

A
  • fires/explosions
  • leachate
  • odors
  • windblown debris
  • pests
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29
Q

Fire/Explosion risk of landfills

A
  • biggest problem
  • due to methane being produced from decomposition of the garbage
  • daily cover to prevent too much CH4 mixing with the air
  • spark from machinery operating at the landfill
  • gas recovery systems (waste to energy initiative)
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30
Q

Leachate problems

A
  • defined as a liquid which has been in contact with waste in the landfill cell and has undergone chemical and physical changes
  • sources include precipitation, decomposition of garbage and compostable materials and from waste itself
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31
Q

Odor problem

A

-controlled with daily cover

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32
Q

Windblown debris problem

A
  • use daily covers
  • nets
  • if waste leaves landfill, landfill is responsible for the cleanup
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33
Q

Pests problem

A
  • use daily cover and waste compaction
  • pests are disease vectors and include rats and sea gulls
  • can’t build a landfill within 1.5 km of an airport owing to sea gulls
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34
Q

Migration routes for contaminants in a landfill

A
  • solution into groundwater
  • soil retention
  • volatilization
  • overland runoff
  • plants
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35
Q

Ground water migration route for contaminants

A

-soluble materials readily dissolve into leachate which can then enter ground water

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36
Q

Soil retention migration route for contaminants

A

-mainly occurs with heavy metals such as Pb, Fe, Cr

37
Q

Volatilization migration route for contaminants

A
  • contamination of air

- eg. CH4, CO2, NH4, H2S

38
Q

Overland Runoff migration route for contaminants

A
  • flooding

- can enter surface bodies of H2O

39
Q

Plants migration route for contaminants

A
  • plants growing in landfill areas may take up heavy metals and other toxic materials
  • if eaten by animals it goes up higher in food chain
40
Q

Landfills clasified based on:

A

what type of area is being filled by the waste

  • Area fill
  • Trench fill
41
Q

Area Fill

A
  • AKA Depression fill

- fill a topographically low area with waste (not allowed in Alberta)

42
Q

Trench Fill

A
  • Used in topographically flat or rolling areas
  • dig a trench, fill with waste
  • cells are the basic building blocks of a trench fill
  • average size 200m x 150m x 15m
43
Q

5 basic design components of a sanitary landfill

A
  1. Liners
  2. Leachate Collection systems
  3. caps and covers
  4. Gas extraction systems
    5, Groundwater monitoring wells
44
Q

The Containment systems is designed to:

A
  • Minimize the amount of leachate formed
  • Prevent the migration of leachate offsite
  • Remove landfill gases before they become a fire or explosion hazard
45
Q

Purpose of a Liner in a landfill

A
  • Prevent migration of leachate out of a landfill’s cells and into the surrounding soil which could result in surface and groundwater contamination
  • Prevent groundwater from entering the cells
46
Q

Location of a liner

A

is along the base and sides of the landfill

47
Q

Materials in Liners

A

Clay
Synthetic
PVC
HDPE

48
Q

Clay Liners

A
  • can either be native clays to the site or brought in
  • must be at least 1 m thick if its the only liner used
  • must be compacted to have a hydraulic conductivity of less than 10 ^ -9 m/s
  • most widely used liner for landfills
49
Q

Problems with Clay Liners

A
  • Cracking
  • Desiccation during construction (liner must be kept moist)
  • Different clays will swell or shrink to different degrees which can cause cracking if different clays are mixed together
50
Q

Synthetic Liners and 2 types of them

A
  • also called geomembranes, geotextiles, FMLs (flexible membrane liners)
  • PVC- Polyvinyl chloride
  • HDPE- high density polyethylene
51
Q

Problems with synthetic liners

A

Can have/get holes

  • while placed on site with heavy equipment
  • Manufacturer defect
  • seams not properly “glued”
  • puncture by waste
52
Q

Combination Liners

A

Geosynthetic clay liners

-made of a thin layer of bentonite (swelling clay found to or fixed between 2 geosynthetic sheets)

53
Q

Double Composite Liner

A
  • consists of 2 composite liners
  • Class I Industrial landfills (ie ones that can accept hazardous waste)
  • waste -> LCS -> Synthetic liner -> Clay liner -> LCS -> Synthetic liner -> clay liner
54
Q

Leachate Collection System (LCS) design

A
  • perforated pipes placed in gravels (high Hydraulic cond.)
  • sump pit and pump station removes collected leachate
  • pipe is angled down to direct leachate flow
55
Q

Leachate Collection System location

A
  • below the waste but above the liners

- between liners in double composite liner

56
Q

4 options for final disposal of leachate

A
  • send to municipal waste water treatment plant
  • Land application
  • leachate recirculation
  • chemical and physical treatment of leachate
57
Q

Land application

A

-limit the number of applications that can be made to a land area due to heavy metal concentration in leachate

58
Q

Leachate recirculation

A
  • land fill treats its own leachate
  • landfill acts like a bioreactor as you recycle leachate through it
  • try to create optimum conditions for microbes to “work”
  • not an option in Vancouver due to high volume of leachate generated due to climate
59
Q

Chemical and Physical Treatment of Leachate

A
  • chemical oxidation
  • chemical precipitation
  • reverse osmosis
  • ammonia stripping
60
Q

Purpose of a cap (cover)

A

To control the migration of

  • moisture (limit precipitation entering as it will increase leachate volumes)
  • gas (prevent it from exiting the landfill as it can create explosive hazards or odors)
61
Q

Cap design

A

Alberta, as specified in the Standards for Landfills in Alberta requires 3 layer landfill

62
Q

Bottom layer of cover

A
  • .6m of barrier with a hydraulic conductivity less than 10^-7 m/s
  • can only be clay or clay and geosynthetic liner
  • prevents gas leaving and water entering
63
Q

Middle layer of cap

A
  • 0.35-0.8 m subsoil

- thickness dependent on the end use of the site after closer

64
Q

Top layer of Cap

A

-.2m topsoil

65
Q

Additional things to a cap

A
  • establish vegetation
  • slope for the final cover
    • 5-30 degrees
    • allows runoff precipitation so it doesn’t pool over waste making more leachate
66
Q

Purpose of Gas Extraction Systems

A
  • remove landfill gases before they become a fire explosion hazard
  • decrease odors
  • minimize subsurface gas migration
  • allow waste to energy management systems to be developed
67
Q

2 types of Gas Extraction Systems

A
  • Active systems- act like a vacuum by creating negative or positive pressure in the landfill pulling the gas out
  • Passive Systems- gas removed based on the pressure it creates naturally in the landfill as it is generated
68
Q

Passive systems include

A
  • Perimeter Interceptor Trenches
  • Flaring
  • Slurry Walls
69
Q

Active Systems include

A
  • perimeter gas extraction trenches

- perimeter gas extraction wells

70
Q

Perimeter Gas Extraction Trenches

A
  • perforated pipe is laid in trenches around the perimeter of the landfill and backfilled with gravel
  • gases migrate laterally through landfill and pulled out by the negative pressure created by a suction blower
71
Q

Perimeter Gas Extraction Wells

A
  • vertical wells are placed outside the landfill perimeter
  • wells are connected by a common header pipe through which the blower pulls the methane from the area of include around each well
72
Q

Perimeter Interceptor Trenches

A
  • gravel packed trench containing perforated pipe surrounding the landfill
  • gases migrate laterally and are removed
  • similar to gravel packed extraction trench but without a pump
73
Q

Flaring

A
  • most common method
  • drill wells into landfill
  • helps decrease lateral methane migration by decreasing pressure with the landfill itself
74
Q

Slurry Walls

A
  • dig a trench outside perimeter
  • fill with an impermeable material (eg bentonite, clay, slurries)
  • gases can’t get beyond walls so migrate to surface
75
Q

Groundwater monitoring wells

A
  • must be placed both up gradient and down gradient of the landfill
  • no more than 200m apart
  • down gradient = detect contaminant plumes
  • up gradient= monitors background levels
76
Q

Minimum Landfill Monitoring Plan

A
  • ground water monitoring plan
  • surface water monitoring plan
  • leachate monitoring plan (if has a leachate collection system)
  • subsurface landfill gas monitoring plan (if accepts organic waste)
77
Q

Daily Landfilling Procedures

A
  • waste is dumped at the base of the work face
  • moved into place and compacted to reduce volume
  • end of each day a layer of soil approx. 6” thick to minimize pests, odors, windblown garbage, fire risk
78
Q

Lift

A

Single layer of waste in a cell

79
Q

Intermediate Cover

A
  • Layer of soil between lifts in a landfill
  • typically 2 lifts/cell
  • once the cell is filled a final cover placed on top
80
Q

3 stages of Waste Decomposition in a Landfill

A
  • Aerobic Decomposition
  • Fermentation
  • Methanogenesis
81
Q

Aerobic Decomposition

A
  • mainly with organic matter
  • approx. 1 month
  • proceeds till all oxygen used up
  • very exothermic –> high potential for fire at this stage
82
Q

Fermentation

A
  • Anaerobic and acetogenic bacteria ferment and hydrolyse organic components to simpler more soluble compounds
  • takes several years
  • begins once oxygen has been depleted
  • Produces acidic leachate (pH 5-6), high BOD (>10, 000 mg/L), Ammonium (500-1000mg/L)
  • releases CO2
  • heavy metals released as a result of acidic leachate
83
Q

Methanogenesis

A
  • associated with slow growing methanogenic bacteria (killed by oxygen, don’t like acidic conditions)
  • methane can be recovered and used as energy source (waste - energy)
  • highly explosive if not vented
  • years to decades
  • main gases CH4 (55%) and CO2 (40%)
84
Q

4 phases of a landfill life

A
  • Active Phase
  • Closure Phase
  • Post-closure phase
  • Eternity Phase
85
Q

Phase I: Active Phase

A

-Operational phase when waste is being collected at the landfill

86
Q

Phase II Closure Phase

A
  • Final Closure plan enacted
  • Reclamation of the site
    • final cover
    • erosion control system
    • restore surface water drainage systems
    • necessary changes to any monitoring systems (grd water, leachate, gas)
    • decommissioning of old buildings and facilities
87
Q

Phase III Post Closure Phase

A
  • Maintain integrity of final cover
  • remediate any areas affect by subsidence and differential settling
  • maintain reclamation systems
  • minimum 25 years OR until
    • grd water standards are met
    • gas [ ] limits below explosive levels
    • leachate [ ] below control limits
    • leachate not naturally occuring aren’t detected
    • volume of leachate collected is qual to or less than the previous year for 5 consecutive years
88
Q

Phase IV Eternity phase

A
  • end use of the site

- had to be determined when the landfill was being done

Waste Management (9 decks)

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