6. Waste Options: Landfills Flashcards

Question

Political/Social issues with Landfill Siting

Answer 1

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

Answer 2

- Site Capacity (Volume) - want 25+ years operational life - Accessibility - don't want too long transport distances --> $ - don't want in residential areas

Answer 3

- 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

Answer 4

- fires/explosions - leachate - odors - windblown debris - pests

Answer 5

- 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)

Answer 6

- 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

Answer 7

-controlled with daily cover

Answer 8

- use daily covers - nets - if waste leaves landfill, landfill is responsible for the cleanup

Answer 9

- 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

Answer 10

- solution into groundwater - soil retention - volatilization - overland runoff - plants

Answer 11

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

Answer 12

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

Answer 13

- contamination of air | - eg. CH4, CO2, NH4, H2S

Answer 14

- flooding | - can enter surface bodies of H2O

Answer 15

- 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

Answer 16

what type of area is being filled by the waste - Area fill - Trench fill

Answer 17

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

Answer 18

- 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

Answer 19

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

Answer 20

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

Answer 21

- 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

Answer 22

is along the base and sides of the landfill

Answer 23

Clay Synthetic PVC HDPE

Answer 24

- 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

Answer 25

- 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

Answer 26

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

Answer 27

Can have/get holes - while placed on site with heavy equipment - Manufacturer defect - seams not properly "glued" - puncture by waste

Answer 28

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

Answer 29

- 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

Answer 30

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

Answer 31

- below the waste but above the liners | - between liners in double composite liner

Answer 32

- send to municipal waste water treatment plant - Land application - leachate recirculation - chemical and physical treatment of leachate

Answer 33

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

Answer 34

- 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

Answer 35

- chemical oxidation - chemical precipitation - reverse osmosis - ammonia stripping

Answer 36

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)

Answer 37

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

Answer 38

- .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

Answer 39

- 0.35-0.8 m subsoil | - thickness dependent on the end use of the site after closer

Answer 40

-.2m topsoil

Answer 41

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

Answer 42

- 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

Answer 43

- 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

Answer 44

- Perimeter Interceptor Trenches - Flaring - Slurry Walls

Answer 45

- perimeter gas extraction trenches | - perimeter gas extraction wells

Answer 46

- 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

Answer 47

- 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

Answer 48

- 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

Answer 49

- most common method - drill wells into landfill - helps decrease lateral methane migration by decreasing pressure with the landfill itself

Answer 50

- dig a trench outside perimeter - fill with an impermeable material (eg bentonite, clay, slurries) - gases can't get beyond walls so migrate to surface

Answer 51

- 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

Answer 52

- 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)

Answer 53

- 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

Answer 54

Single layer of waste in a cell

Answer 55

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

Answer 56

- Aerobic Decomposition - Fermentation - Methanogenesis

Answer 57

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

Answer 58

- 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

Answer 59

- 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%)

Answer 60

- Active Phase - Closure Phase - Post-closure phase - Eternity Phase

Answer 61

-Operational phase when waste is being collected at the landfill

Answer 62

- 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

Answer 63

- 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

Answer 64

- end use of the site | - had to be determined when the landfill was being done

6. Waste Options: Landfills Flashcards

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