solid waste & hazardous waste

solid & Hazardous waste 1

Solid Waste & Hazardous Waste

Hikmat Al Salim

March 20123/9/2012

Waste Classification

• Municipal waste• Construction demolition

debris • Nonhazardous industrial

waste• Incineration ash• Hazardous waste

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.

solid & Hazardous waste 4

A waste is classified as a hazardous if it has a hazardous characteristic listed below.

1. Hazardous Characteristics:

• Ignitable Hazardous Waste (TRIC)– A liquid waste which has a flash point of less

than or equal to 140 degrees F (60 degrees C) as determined by an approved test method.

– A non-liquid waste which, under standard conditions, is capable of causing a fire through friction, absorption of moisture or a spontaneous chemical change and when ignited, the waste burns so vigorously and persistently that it creates a hazard.

– An ignitable compressed gas or oxidizer.March 20123/9/2012

solid & Hazardous waste 5

2. Corrosive Hazardous Waste (TRIC)

– An aqueous waste with a pH of less than or equal to 2 or greater than or equal to 12.5 is considered to be a corrosive hazardous waste.

– A liquid waste that corrodes steel at a minimum rate of .25 inch per year as determined by an approved test method.

March 20123/9/2012

solid & Hazardous waste 6

(TRIC)

3. Reactive Hazardous Waste– A solid waste that is normally unstable,

reacts violently with water, or generates toxic gases when exposed to water or other materials.

4. Toxic Hazardous Waste– A waste that contains certain

substances determined to be harmful at or in excess of the maximum concentration. Some of those substances include lead, arsenic, and mercury.

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Nature of Waste Problem

March 20123/9/2012

· 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

Outlines

• Waste management methods• Landfill design and regulations• Function and usage of

geosynthetics in landfill systems• Durability of geosynthetics• Future trend of landfill

management

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.

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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• Destruction of wastes by Combustion• The method is suitable for:

–– Gases–– Liquids–– Slurries–– Sludge wastes–– Solids–– Containerized

• Incineration destroys molecular structure, thus molecules with more stable structures and stronger chemical bonds require longer residence times and/or higher temperatures.

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• Incinerator operating conditions must be monitored continuously. The following are some parameters affecting the efficiency of burning:

Combustion temperatureResidence timeDegree of mixingPresence of excess air

• The type of incinerator required depends on the chemic and physical state of "waste" :

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• Liquid injection– Any pumpable waste– Converts liquid waste to gas prior to combustion

Kilns– Used on solids, liquids, and gases– Many different types (e.g., rotary kilns, cement kilns, lime kilns,aggregate kilns).

Calcination or sintering• – 1800oC and atmospheric pressure.• – Destroys organics; reduces the volume of

inorganics• Incinerator Performance must be monitored,

thus:March 20123/9/2012

solid & Hazardous waste 14

• Destruction and Removal Efficiency (DRE) must be determined. This done by "monitoring" organization. The higher the figure of DRE , the more efficient is the incinerator. DRE of 99.99% for all “principal organic hazardous constituents” (POHCs) is required.

• – Example: Wastes containing dioxins and furans

requires 99.9999% DRE

March 20123/9/2012

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• Incomplete combustion – afterburners must be installed for exhaust

• – Combust the exhaust at higher temperature than the combustion of primary waste stream. Example: dioxin and furan creation, more toxic than precursors

• 75 dioxin congeners; 135 furan congeners• Incinerators usually produce particulates; thus

particulate controls are important. Particulates can be removed by using bag-houses, and water scrubbers

• Control of acid formation is also important e.g. HCl from combustion of chlorinated organics. Acids corrode metals and form "acid precipitates", and acid rain.

• .

March 20123/9/2012

  Congeners are toxic chemicals that are formed during incineration.  A member of the same kind, class, or group

solid & Hazardous waste 16

Municipal Solid Waste DisposalINCINIRATION

March 20123/9/2012

solid & Hazardous waste 17March 20123/9/2012

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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solid & Hazardous waste 20March 20123/9/2012

The Largest Landfill

• Staten Island, NY

• 3,000 acres• 2.4 billion

cubic feet of waste

• 25 times of the great pyramid

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

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.

Minimum Technology Guidance (MTG) for a Subtitle D Landfill

“Solid Waste”

150 mm

300 mm

600 mm

Filter (or GT)

Drain (or GN/GC)

Clay @ 1x10-7 cm/sec

Soil Subgrade

GM*

GT (opt.)

Compositeliner

MTG for a Subtitle C Landfill

300 mm Drain (or GN)S-GM*

“Solid Waste”

150 mm

300 mm

900 mm

Filter (or GT)

Drain (or GN/GC)

Clay @ 1x10-7 cm/sec

(to highest groundwater level)

P-GM*

3.0 m

Compositeliner

Landfill Covers(Non-hazardous landfill without

Geosynthetic on the bottom liner system)

Erosion Layer

Infiltration Layer

150 mm

450 mm

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

Landfill Cover System(Subtitle C & D, and Corp of Eng.)

300 mm Drain (or GN)

150 mm

150 mm

600 to900 mm

Topsoil

Filter (or GT)

Clay @ 1x10-7 cm/sec

”Solid Waste”

Varies(frost depth) Cover Soil

300 mm Gas Vent (or GT)

GM

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

Geosynthetics

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

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 = filtrationD = drainage, B = barrier

Liner System

GT

GG

GN

GCL

GM

CCL

Gravel w/ perforated pipe

Final Cover System

Geosynthetic ECM

GP or GC

GT

GG

Cover Soil

GCL

GM

GC or GN

Solid Waste

Composite Barriers(Intimate Contact Issue)

Leachate

CCL

Clay Liner(by itself)

Leachate

CCL

Composite Liner(with intimate contact)

Does the GT compromise the composite liner concept?Ans: Generally no...

Leachate

Composite Liner(GM + GCL)

GCL

Composite Barriers(Theoretical Leakage)

GM alone (hole area “a”)

Leachate

ks

Composite liner (GM/CCL)

Q C a ghB= 2 Q = 0.21 a0.1 h0.9

ks0.74

(for good contact)Q = 1.15 a0.1 h0.9

ks0.74

(for poor contact)Ref. Bonaparte, Giroud & Gross, GS ‘89)

Average Values of Leakage Quantities

Life Cycle Stage

Leakag

e R

ate

(lp

hd

)

3210

10

20

30

40

GM

GM/CCL

GM/GCL

SandLeak Detection

Average Values of Leakage Quantities (cont’d)

Life Cycle Stage

Leakag

e R

ate

(lp

had

)

3210

5

10

15

20

GM

GM/CCL

GM/GCL

GeonetLeak Detection

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)

Compositions(approximate percentage)

Type Resin CarbonBlack

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

Material Properties

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

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

Design Concept

FSAllowable   (Test)   PropertyRequired  (Design)   Property

=FSAllowable   (Test)   PropertyRequired  (Design)   Property

=

Where:

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

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%.

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.

Carbon Black

• Carbon black content is measured according to ASTM D1603.

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

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.

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.

Degradation of HDPE Geomembranes

Chemical Related:–Thermal-oxidation–Photo-oxidation

Linear PE Structure

• Linear PE is a graft copolymer• Each co-monomer creates one

branch• Co-monomer can be butene,

hexene, or octene

C C C C

H

H

H H

H H H

CC

CC

Density of Geomembranes

• Density decreases as the amount of co-monomer increases

• Density range of PE (ASTM D883)

–> 0.940 g/ml for HDPE –0.926 - 0.940 g/ml for MDPE–0.910 - 0.925 g/ml for LLDPE–<0.909 g/ml for VLDPE or

ULDPE

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.

Forming Free Radicals

C C C C

H

H

H H

H H H

CC

C

C

Different Degradation Stages

InductionPeriod

DegradationPeriod

Aging Time (log)

Prop

erty

Ret

aine

d (%

)

Unstabi l ized Polyethylene

I nduct i onPeri od

DegradationPeriod

Aging Time (log)

Prop

erty

Ret

aine

d (%

)

stabi l ized Polyethylene

AntioxidantDepletion Period

Various Stages of Oxidation

Aging Time

Antioxidantdepletion time

Acceleration period

Deceleration period

(b)

Oxy

gen

Abs

orpt

ion

Induction period

Induction period

Acceleration period

Deceleration period

Oxy

gen

Abs

orpt

ion

(a)

Reactions during Induction Period

RH R H R O ROO 2

ROO RH ROOH R

Reactions during Acceleration Period

ROOH RO OH

RO RH ROH R

OH RH H O R 2

Functions of Antioxidants

• Primary antioxidants react with free radical species

• Secondary antioxidants decompose ROOH to prevent formation of free radicals

R• ROO•

ROOH RH

RO• + •OH

O2

(2)

(3)

(4)

RH

(1)

(5) & (6)

ROH & H O2

(a)

(b)

A

B

(c)

(d)

RH

Types of Antioxidants

Category Chemical Type Example

Primary Hindered phenol Irganox 1076 or 1010Santowhite crystals

Hindered amines Various of Tinuvin, Chemassorb 944

Secondary Phosphites Irgafos 168

Sulfur compound Dilauryl thiodipropionateDistearyl thiodipropionate

Hindered amines Various of Tinuvin, Chemassorb 944

Effective Temperature Range

0 50 100 150 200 250 300

Phosphites

Hindered Phenols

Thiosynergists

Hindered Amines

Temperature (oC)

Depletion of Antioxidants

Two mechanisms:

a. Chemical reactions – by reacting with free radicals and peroxides

b. Physical loss – by extraction or volatilization

Arrhenius Model

Rate of reaction = X * Y * Z

Where:X = collision frequency (concentration

or pressure)Y = energy factorZ = probability factor of colliding

particles (temperature dependent)

Potential Energy

DH

Eact

transition state

products ofreaction

SeparateReactantsPo

tenti

al E

nerg

y

Progress of Reaction

Distribution of Energy

dNdE

Energy

Fraction is-EactRT

exp( )

Arrhenius Equation

R X e Zr

E

RTact

( )( )( )

R A er

E

RTact

( )( )

(9)

(10)

ln lnR AE

RTract (11)

Arrhenius Plot

A

ln Rr 1

E act

R

high temperature(lab tests)

low temperature(site temperature)

Inverse Temperature (1/T)

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

Piezometer

Insulation

Perforated steel loading plate

Sand

Sand

Heat tape

Geomembrane

Load

1 10

Incubation Device

Tests Performed

• Oxidative inductive time (OIT) for antioxidant content.

• Melt index for qualitative molecular weight measurement.

• Tensile test for mechanical property

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.

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

Thermal Curve of OIT Test

T im e (m in )

Ex

oth

erm

En

do

the

rm

N23 5 k Pa

O2

In te rc e p t

Ox id a tiv eRe a c tio n

2 0 0 °C

Is o th e rm a l

OIT

a t 3 5 k Pa

Test Results

3025201510500

50

100

150

Std-OITHP-OITDensityMelt IndexYield StressYield StrainBreak StressBreak Strain

Incubation Time (month)

Pe

rce

nt

Re

tain

ed

Changes in Eight Properties with Incubation Time at 85°C

Analysis of OIT Data

a. Determine OIT depletion rate at each temperature.

b. Utilize Arrhenius Equation to extrapolate the depletion rate to a lower temperature.

c. Predict the time to consume all antioxidant in the polymer.

a) - OIT Depletion Rate

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25

55°C65°C75°C85°C

ln O

IT (

min

.)

Incubation Time (month)

b) –Arrhenius Plot

0.00310.00300.00290.00280.0027-5

-4

-3

-2

-1Standard OIT

HP-OIT

1/T (°K)

ln (O

IT Dep

letio

n Ra

te)

y = 17.045 - 6798.2x R^2 = 0.953

y = 16.856 - 6991.3x R^2 = 0.943

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

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.

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.

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.”

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

Status

• 1993 - less than 20 landfills recirculating leachate

• 1997 - ~ 130 landfills recirculating leachate

• My estimate - ~ 5% of landfills

Aerobic Bioreactor

• Rapid stabilization of waste• Enhanced settlement• Evaporation of moisture• Degradation of organics which are

recalcitrant under anaerobic conditions

• Reduction of methane emissions

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?