WASTE CONTAINMENT TECHNOLOGY

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WASTE CONTAINMENT TECHNOLOGY

• Dr. Grace Hsuan
• Civil Architectural Engineering

2
Outlines

• Waste management methods
• Landfill design and regulations
• Function and usage of geosynthetics in landfill
  systems
• Durability of geosynthetics
• Future trend of landfill management

3
Waste Classification

• Municipal waste
• Construction demolition debris
• Nonhazardous industrial waste
• Incineration ash
• Hazardous waste

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Amount of Municipal Waste
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Waste Management Methods
Method 1970 1980 1990 1992 (Goal)
Landfilling 72 81 67 55
Combustion 21 9 16 20
Recycling 7 10 17 25
 
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Source Reduction

• Source reduction involves reduction in the
• quantity or toxicity of materials during the
• manufacturing process via
• Decrease the amount of unqualified products by
  improving quality control
• Decrease the unit weight of the product by using
  high quality material.

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Weight Reduction (unit of grams)
Container 1980 1992
2-liter PET bottle 65 51
Aluminum can 19 15
Glass soda bottle 255 177
Steel (tin) soup can 48 37
Half-pint milk carton 14 11
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Recycling Materials in Percentage of Waste
Materials 1985 1990 Projected 1992
Corrugated boxes 4.4 5.9 6.7
Newspapers 2.1 2.8 3.3
Office paper 0.7 0.9 1.0
Glass containers 0.7 1.3 1.5
Steel cans 0.1 0.2 0.2
Aluminum cans 0.4 0.5 0.5
Plastics packaging 0.1 0.2 0.2
Yard waste 0 2.2 2.7
Others 1.5 3.0 3.8
Total 10 17.1 20.2
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Combustion

• Combustion can reduce the volume of the solid
  waste up to 90 at the same generate power.
• There are 140 combustion plants the US.
• Emission must meet the EPA Clean Air Act.
• Residual ash is hazardous material and should be
  disposed accordingly.

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Landfill

• Landfill implies disposal of waste in the ground.
• 70 of the waste is disposed in landfill and the
  percentage has been gradually decreasing.
• The amount of waste actually increased due to
  population growth.

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Landfilling

• Approximately 6,500 landfills operate in the US
• 57 belong to local governments
• 14 belong to private companies,
• 29 belong to federal agencies or solid waste
  authorities.

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Landfill Capacity

• The size and capacity vary greatly
• 30 of the landfills receive less
• than 30 tons per day
• 5 receive more than 500 tons

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The Largest Landfill

• Fresh Kills,
• Staten Island, NY
• 3,000 acres
• 2.4 billion cubic feet of waste
• 25 times of the great pyramid

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Nature of Waste Problem

• Moisture within and flowing on the waste
  generates leachate
• Leachate takes the characteristics of the waste
• Thus leachate is very variable and is
  site-specific - there is no "typical" leachate
• Flows gravitationally downward into the leachate
  collection system
• Enters groundwater unless a suitable barrier
  layer or system is provided

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Current Legislation

• EPA for both non-hazardous and hazardous waste
• Superfund via Corps of Engineers
• DOE/NRC for radioactive wastes
• Worldwide approx. 40 countries have
  legislation/regulations (survey in GRI Report 23)

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Regulations

• Solid waste is regulated under the Resource
  Conservation and Recovery Act (RCRA).
• Classification of non-hazardous and hazardous
  waste depends on the chemical constituents of the
  leachate.

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Hazardous Waste Definition

• Waste is listed in Appendix VIII of Title 40,
  Code of Federal Regulations, Part 251.
• Waste is mixed with or derived from hazardous
  waste.
• Waste is not identified as municipal waste.
• Waste possesses one of the following
  characteristics
• ignitable corrosive reactive and toxic.

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Minimum Technology Guidance(MTG)

• Federal regulation on landfill design requirement
  is published by the EPA.
• Dependent on the classification of the waste, MTG
  is recommended.
• Each state must follows, or exceed, the MTG.

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Non-hazardous Waste

• Non-hazardous waste is regulated under Subtitle D
  of RCRA.
• EPA regulations are published in Parts 257 and
  258, Title 40, Code of Federal Regulations (CFR).

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Minimum Technology Guidance (MTG) for a Subtitle
D Landfill
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Hazardous Waste

• Hazardous waste is regulated under Subtitle C of
  RCRA.
• EPA regulations are published in Part 264.221,
  Title 40, Code of Federal Regulations (CFR).

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MTG for a Subtitle C Landfill
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Landfill Closure Activities

• Closure must begin within 30 days of final
  receipt of waste extensions may be granted by
  state approval.
• Closure must be completed in accordance with
  closure plan within 180 days extensions may be
  granted by state approval.
• A notation must be placed in the deed.

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Landfill Covers(Non-hazardous landfill without
Geosynthetic on the bottom liner system)
Erosion Layer
150 mm
Infiltration Layer
450 mm
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Cover Layers

• Erosion Layer
• Earthen material is capable of sustaining native
  plant growth
• Infiltration Layer
• Permeability of this layer of soil should be less
  than or equal to the permeability of any bottom
  liner system or natural subsoils present, or
  permeability less than 1x10-5 cm/sec whichever is
  less

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Landfill Cover System(Subtitle C D, and Corp
of Eng.)
150 mm
Topsoil
Varies (frost depth)
Cover Soil
150 mm
Filter (or GT)
300 mm
Drain (or GN)
GM
600 to 900 mm
Clay _at_ 1x10-7 cm/sec
300 mm
Gas Vent (or GT)
Solid Waste
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Landfill Site

• Conforms with land use planning of the area
• Easy access to vehicles during the operation of
  the landfill
• Adequate quantity of earth cover material that is
  easily handled and compacted
• Landfill operation will not detrimentally impact
  surrounding environment
• Large enough to hold community waste for some time

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Geosynthetics

• geomembranes (GM)
• geosynthetic clay liners (GCL)
• geonets (GN)
• geotextiles (GT)
• geogrids (GG)
• geopipe (GP)
• geocomposites (GC)

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Primary Functions
Type S R F D B
GM - - - - Y
GCL - - - - Y
GN - - - Y -
GT Y Y Y Y -
GG - Y - - -
GP - - - Y -
GC Y Y Y Y Y
S separation, R reinforcement, F
filtration D drainage, B barrier
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Natural Soils vs. GSs
Function Natural Soil Geosynthetics
Barrier-Single CCL GM
Barrier- Composite GM/CCL GM/GCL GM/GCL/CCL
Drainage Layer Sand Gravel or sand GT GN
Filter Layer Sand GT
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Liner System
GT
GN
GCL
Gravel w/ perforated pipe
GM
GG
CCL
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Final Cover System
GG
Geosynthetic ECM
Cover Soil
GC or GN
GT
GM
GCL
GP or GC
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Solid Waste
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Possible Geosynthetic Layersin a Waste
Containment System

• in Final Cover - 7
• in Base Liner - 9
• 16 Layers!

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Liquid Barrier Systems

• Single CCL
• Single GM
• Single composite liner
• GM/CCL
• Double composite liner
• GM/CCL-GM/CCL
• GM/GCL-GM/CCL

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Composite Barriers(Intimate Contact Issue)
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Composite Barriers(Theoretical Leakage)
GM alone (hole area a)
Composite liner (GM/CCL)
Leachate
ks

Q 0.21 a0.1 h0.9 ks0.74 (for good contact)
Q
C
a
gh
2
B
Q 1.15 a0.1 h0.9 ks0.74 (for poor contact)
Ref. Bonaparte, Giroud Gross, GS 89)
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Generalized Leakage Rates Through Liners(ref.
Giroud and Bonaparte, Jour. G G, 1989)
assumes 3 holes/ha (i.e., 1.0 hole/acre)
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Response Action Plans (RAP's)

• Only applicable with double liner systems
• Worldwide, 58 HSW (incl. USA) and 14 of MSW
  require double liner systems
• Requires measurement of liquid quantity in leak
  detection system
• If above the preset action leakage rate (ALR),
  different requirements are set in motion, e.g.,
• continuous monitoring
• characterize liquid
• stop receiving waste
• remove waste to locate leak(s)

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Some Comments on RAP's

• (a) "de minimum" leakage 10 lphd ( 1.0 gpad)
• vapor diffusion through perfect geomembrane with
  no flaws 0.2 to 20 lphd
• (b) typ. action leakage rate (ALR) 50 to 200
• continuous monitoring
• assess liquid characteristics
• compare to primary leachate
• (c) typ. intermediate leakage rate (ILR) 200 to
  1000
• stop adding waste
• continue monitoring and testing
• (d) typ. rapid and large leak (RLL) gt 1000 lphd
• remove waste
• repair leak(s)

Note all of the above RAP values are for
illustration only -- they must be site
specifically determined -- note that EPA only
requires the establishment of an ALR value
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Average Values of Leakage Quantities
Sand Leak Detection
GM
Leakage Rate (lphd)
GM/CCL
GM/GCL
3
2
1
Life Cycle Stage
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Average Values of Leakage Quantities (contd)
Geonet Leak Detection
GM/CCL
Leakage Rate (lphad)
GM
GM/GCL
3
2
1
Life Cycle Stage
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Geomembranes
Widely Used Geomembranes Limited Used Geomembranes
High density polyethylene (HDPE) Chlorosulfonated polyethylene (CSPE)
Linear low density polyethylene (LLDPE) Ethylene interpolymer alloy (EIA)
Flexible polypropylene (f-PP) Ethylene propylene trimonomer (EPDM)
Polyvinyl chloride-plasticized (PVC-p)
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Comments

• Name is associated with resin type
• All have some amount of additives
• Additives can vary from 2 to 60
• Some additives are critical to performance

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Compositions(approximate percentage)
Type Resin Carbon Black Plasticizer Anti-oxidant Filler
HDPE 95-97 2-3 0 1-0.5 0
LLDPE 95-97 2-3 0 1-0.5 0
PVC-p 50-70 1-2 25-35 1-0.5 5-10
fPP 95-97 2-3 0 1-0.5 0
CSPE 40-60 5-40 0 1-0.5 5-15
EPDM 25-30 20-40 0 1-0.5 20-40
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Geomembrane Styles

• smooth geomembranes
• Textured geomembranes
• Reinforced geomembranes

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Manufacturing Processes

• Flat extrusion
• Blown sheet extrusion
• Blown sheet co-extrusion
• Calendaring

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Material Properties

• Mechanical property
• Density
• Melt flow
• Carbon black
• Plasticizers
• Antioxidant

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Tensile Behavior

• Test method varies according to the resin type
  and style of the geomembrane.
• Each test method consists of unique shape of
  specimen and strain rate.
• Methods
• HDPE, LLDPE and fPP ASTM D 638 Type IV
• PVC-p ASTM D 882
• All reinforced geomembranes ASTM D 751

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Design Concept

(Test)

(Test)
Allowable
Property
Allowable
Property


FS
FS
Required
(Design)

Property
Required
(Design)

Property

• Where
• Test methods are from ASTM, ISO, or others
• Design models from the literatures
• Factor-of-Safety is site specific

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Density Methods

• ASTM D 752 (Specific gravity)
• ASTM D 1505 (Density column)
• ASTM D 4883 (Ultrasonic for PE only)

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HDPE Geomembranes

• Resin density is around 0.930 g/cc, which is in
  the medium density range according to ASTM D 833.
• The 2.5 carbon black raise the density of the
  product to 0.941g/cc, which is the HDPE range.
• ?product ?resin 0.0044C
• Where C weight percentage of carbon
  black

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Melt Flow (MI) Method

• Test Method - ASTM D 1238
• Only for thermoplastic materials
• Test condition varies with resin type
• It is essential for extrusion process, i.e., for
  product manufacturers
• For the same type of polymer, MI can be
  correlated to the molecular weight

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Function of Carbon Black

• The primary function is as an ultraviolet light
  stabilizer to protect polymer being degraded.
• Carbon black absorption coefficient increases
  with loading up to 3.
• In elastomeric materials, carbon black also
  functions as an reinforcement, and loading can be
  as high as 30-40.

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Addition of Carbon Black

• The masterbatch technique is utilize to
  dispersing carbon black in plastic.
• A masterbatch is a resin containing a high
  concentration of carbon black.
• The masterbatch is blended with polymer resin to
  achieve the desire percentage.

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Carbon Black

• Carbon black content is measured according to
  ASTM D1603.
• Carbon black dispersion is evaluated according to
  ASTM D 5596.

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Plasticizers

• Plasticizers is used in PVC to lower the glass
  transition temperature (Tg).
• An addition of 30 plasticizer in PVC can lower
  the Tg from 80oC to 20oC.
• The plasticized PVC behaves rubbery at normal
  ambient temperature.
• However, plasticizer can slowly leach out with
  time.

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Analysis Plasticizers

• The amount of plasticizer in the polymer can be
  determine by extraction according to ASTM D 2124.
• The type of plasticizer can be identified using
  Infrared (IR) spectroscopic.

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Antioxidants

• The function of antioxidants is to protect
  polymers from being oxidized during the extrusion
  process and service lifetime.
• For polyolefines, antioxidants is vital to the
  longevity of the product.
• Antioxidant will be the focus of the second part
  of this class.

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Degradation of HDPE Geomembranes

• Chemical Related
• Thermal-oxidation
• Photo-oxidation

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Linear PE Structure

• Linear PE is a graft copolymer
• Each co-monomer creates one branch
• Co-monomer can be butene, hexene, or octene

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Density of Geomembranes

• Density decreases as the amount of co-monomer
  increases
• Density range of PE (ASTM D883)
• gt 0.940 g/ml for HDPE
• 0.926 - 0.940 g/ml for MDPE
• 0.910 - 0.925 g/ml for LLDPE
• lt0.909 g/ml for VLDPE or ULDPE

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II. Oxidation Degradation

• Polyolefins, such as HDPE, PP and PB are
  susceptible to oxidation.
• Oxidation takes place via free radical reactions.
• Free radicals form at the tertiary carbon atoms
  (i.e., at branches).
• Oxidation leads to chain scission that results in
  decrease of Mw and subsequently on mechanical
  properties.

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Forming Free Radicals
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Different Degradation Stages
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Various Stages of Oxidation
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Reactions during Induction Period
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Reactions during Acceleration Period
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Functions of Antioxidants

• Primary antioxidants react with free radical
  species
• Secondary antioxidants decompose ROOH to prevent
  formation of free radicals

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Types of Antioxidants
Category Chemical Type Example
Primary Hindered phenol Irganox? 1076 or 1010 Santowhite crystals
Primary Hindered amines Various of Tinuvin?, Chemassorb? 944
Secondary Phosphites Irgafos? 168
Secondary Sulfur compound Dilauryl thiodipropionate Distearyl thiodipropionate
Secondary Hindered amines Various of Tinuvin?, Chemassorb? 944
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Effective Temperature Range
Phosphites
Hindered Phenols
Thiosynergists
Hindered Amines
50
200
0
100
150
250
300
Temperature (oC)
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Depletion of Antioxidants

• Two mechanisms
• Chemical reactions by reacting with free
  radicals and peroxides
• Physical loss by extraction or volatilization

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Arrhenius Model

• Rate of reaction X Y Z
• Where
• X collision frequency (concentration or
  pressure)
• Y energy factor
• Z probability factor of colliding particles
  (temperature dependent)

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Potential Energy
transition state
E
act
Potential Energy
Separate
Reactants
products of
reaction
D
H
Progress of Reaction
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Distribution of Energy
-E
dN
act
Fraction is
exp( )
dE
RT
Energy
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Arrhenius Equation
(9)
(10)
(11)
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Arrhenius Plot
A
E
act
R
ln R
r
1
high temperature
low temperature
(lab tests)
(site temperature)
Inverse Temperature (1/T)
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Experimental Design

• Incubation environment should simulate the field
  (i.e., landfill environment)
• Limited Oxygen
• Some degree of liquid extraction
• Utilize elevated temperatures to accelerate the
  reactions.
• 55, 65, 75, and 85oC

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Incubation Device
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Tests Performed

• Oxidative inductive time (OIT) for antioxidant
  content.
• Melt index for qualitative molecular weight
  measurement.
• Tensile test for mechanical property

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OIT Tests

• OIT is the time required for the polymer to be
  oxidized under a specific test condition.
• OIT value indicates the total amount (not the
  type) of the antioxidant remaining in the polymer.

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OIT Test for Evaluation of Antioxidant (AO)

• OIT Tests
• ASTM D3895-Standard OIT (Std-OIT), or
• ASTM D 5885-High Pressure OIT (HP-OIT)
• HP-OIT test is used for AOs which are sensitive
  to high temperature testing

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Thermal Curve of OIT Test
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Test Results
Percent Retained
Incubation Time (month)
Changes in Eight Properties with Incubation Time
at 85C
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Analysis of OIT Data

1. Determine OIT depletion rate at each temperature.
2. Utilize Arrhenius Equation to extrapolate the
   depletion rate to a lower temperature.
3. Predict the time to consume all antioxidant in
   the polymer.

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a) - OIT Depletion Rate
89
b) Arrhenius Plot
y 17.045 - 6798.2x R2 0.953
y 16.856 - 6991.3x R2 0.943
ln (OIT Depletion Rate)
1/T (K)
90
c) Lifetime of Antioxidant

• Use the OIT depletion equation to find t
• ln(OIT) ln(P) (S) (t)
• The OIT value for unstabilized PE is 0.5 min.
• For this particular stabilization package
• t 200 years

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Lifetime of Geomembrane

• Induction time and degradation period (Stages B
  C) can be established by using unstabilized
  polymer in the experiment.
• It was found by Gedde et al. (1994) that the
  duration of Stages B and C is significant shorter
  than that of Stage A.
• Antioxidants are critical to the long-term
  performance of polyethylene and other
  polyolefines.

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Future of Waste Containment

• Current waste containment technique is defined as
  dry dome method by eliminating leachate from
  being generated after closure.
• Waste will not degrade since moisture is a
  critical component of the biodegradation process.

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Bioreactor Landfill

• a sanitary landfill operated for the purpose
  of transforming and stabilizing the readily and
  moderately decomposable organic waste
  constituents within five to ten years following
  closure by purposeful control to enhance
  microbiological processes. The bioreactor
  landfill significantly increases the extent of
  waste decomposition, conversion rates and process
  effectiveness over what would otherwise occur
  within the landfill.

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Why Operate a Landfill as a Bioreactor?

• to increase potential for waste to energy
  conversion,
• to store and/or treat leachate,
• to recover air space, and
• to ensure sustainability

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Status

• 1993 - less than 20 landfills recirculating
  leachate
• 1997 - 130 landfills recirculating leachate
• My estimate - 5 of landfills

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Aerobic Bioreactor

• Rapid stabilization of waste
• Enhanced settlement
• Evaporation of moisture
• Degradation of organics which are recalcitrant
  under anaerobic conditions
• Reduction of methane emissions

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Research Issues - Aerobic Bioreactor

• How much air is needed?
• How can air be delivered?
• What is the impact on the water balance?
• How are landfill fires prevented?
• What are the economic implications?