THE BIOREACTOR LANDFILL PARADIGM

Frederick G. Pohland, Ph.D., P.E.Professor and Weidlein Chair of Environmental

EngineeringUniversity of Pittsburgh

Pittsburgh, PA 15261, USA

2003 EPA Bioreactor Landfills WorkshopArlington, VA

OUTLINE OF PRESENTATION

• Fundamental Definitions

• From the Way We Were

• Today and Beyond

FUNDAMENTAL DEFINITIONS

• Reactor– a containment structure in which reactions are initiated and

controlled to optimize a desired outcome

• Bioreactor– a biologically-mediated reactor

• Bioreactor Landfill– a bioreactor where the containment structure is a landfill or a

portion of a landfill

FUNDAMENTAL DEFINITIONS (Cont’d.)

• Paradigm– an example, model or archetype of which all things of the same

type are representatives or copies

• Bioreactor Landfill Paradigm– a landfill archetype with leachate recirculation to accelerate

and/or enhance biodegradation and stabilization

FROM THE WAY WE WERE

• Past Landfill Practices– uncontrolled dumping/impacts

• The Emergence of a Paradigm– leachate and gas management– engineered landfill systems

• Scientific and Technical Renaissance– translation of fundamental scientific principles into rationale

design, operation and control

• Regulatory Impacts– away from command and control

H2 HAc

Fe(II)NH3H2SN2

ORGANIC POLYMER-CONTAININGWASTE

MONOMERS

ALCOHOLS

ORGANIC ACIDS

Fe(III)NO3

-

SO42-

HCO3-

CH4

H2O

Legend

: Electron donors

: Electron acceptors

: Precursor byproducts

: End products

Waste Conversion Sequences in Landfill Bioreactor Systems

Stabilization characteristics within a bioreactor landfill unit

Stabilization Time, Days

Gas

Com

posi

tion,

% b

y Vo

lum

e

0

20

40

60

80

100

CO

D, T

VA, g

/L

0

10

20

30

40

50

Incr

emen

tal G

as P

rodu

ctio

n, m

3

0.0

0.2

0.4

0.6

0.8

1.0

pH

5

6

7

8

Amm

onia

, mg/

L

0

1000

2000

3000

OR

P, m

V Ec

-150

-100

-50

0

50

100

150

pH

Ammonia

ORP

N2

COD

O2

TVA

H2

CH4

CO2

Incremental Gas Production

O2

Phase IInitial

Phase IITransition

Phase IIIAcid

Formation

Phase IVMethane Fermentation

Phase VFinal

Maturation

0 200 400 600

Sulfi

de, m

g/L

0510152025

H2S

Note: a pH 7, 1 atm, 1 kg/mol activity, 25oC

-1,120.52NO3- + 5H2 + 2H+ ↔ N2 + 6H2ONitrate ↔ Nitrogen Gas

-511.4CH3COO- + NO3- + H+ + H2O ↔ 2HCO3

- + NH4+

-599.6NO3- + 4H2 + 2H+ ↔ NH4

+ + 3H2O

Nitrate ↔ Ammonia

-59.9CH3COO- + SO42- + H+ ↔ 2HCO3

- + H2S

-151.9SO42- + 4H2 + H+ ↔ HS- + 4H2O

Sulfate ↔ Sulfide

-135.6HCO3- + 4H2 +H+ ↔ CH4 + 3H2OHCO3

- ↔ Methane

-104.62HCO3- + 4H2 + H+ ↔ CH3COO- + 4H2OHCO3

- ↔ Acetate

Reductions (Electron Accepting Reactions)a

-31.0CH3COO- + H2O ↔ HCO3- + CH4Acetate ↔ Methane

-4.2CH3CHOHCOO- + 2H2O ↔ CH3COO- + HCO3- + H+ + 2H2Lactate ↔ Acetate

+9.6CH3CH2OH + H2O ↔ CH3COO- +H+ + 2H2Ethanol ↔ Acetate

+48.1CH3CH2CH2COO- + 2H2O ↔ 2CH3COO- + H+ + 2H2Butyrate ↔ Acetate

+76.1CH3CH2COO- + 3H2O ↔ CH3COO- + HCO3- + H+ + 3H2Propionate ↔ Acetate

+48.4CH3(CH2)4COO- + 2H2O ↔ CH3(CH2)2COO- + CH3COO- + H+ + 2H2Caproate ↔ Butyrate + Acetate

+96.7CH3(CH2)4COO- + 4H2O ↔ 3CH3COO- + 2H+ + 4H2Caproate ↔ Acetate

+48.3CH3(CH2)4COO- +2H2O ↔ 2CH3CH2COO- + H+ +2H2Caproate ↔ Propionate

∆G, kJOxidations (Electron Donating Reactions)a

Redox Half-reaction Responsible during Anaerobic Stabilization in Bioreactor Landfills

Bioreactor landfill attenuation of representative recalcitrant organic and inorganic constituents*

* References: Pohland et al. (2002).** Perchloroethene (PCE), Trichloroethene (TCE), Dibromomethane (DBM), Hexachlorobenzene (HCB), Trichlorobenzene (TCB), Dichlorobenzene (DCB), Dichlorophenol

(DCP), Nitrophenol (NP), Nitrobenzene (NB), Bis (2-ethylhexyl)phthalate (BEHP), Naphthalene (NAP), Lindane (LIN), Diedrin (DIEL); includes daughter products.

Conversion to a reduced oxidation state with complex formation and volatilization (Fe, Cr, Hg).

Mobilization and salt formation in leachate in the presence of organic (e.g., aromatic hydroxide, carboxylic acid, aromatic amine, humic and fulvic acid) and inorganic (e.g., chloride, sulfate, carbonate) ligands.

Formation of sparingly soluble hydroxides (Cr) and sulfates (Cd, Cu, Fe, Hg, Ni, Pb, Zn) after sulfate reduction, and precipitation.

Physical sorption and ion exchange within the waste matrix.Filtration and retention within stagnant pools of interstitial water.

Heavy Metals(Cd, Cu, Cr, Fe, Hg, Ni, Pb, Zn)

Low volatility and mobility in gas and leachate prior to complete or partial biodegradation.Phthalate Esters (BEHP), Polynuclear Aromatics (NAP), and Pesticides (LIN, DIEL)

Mobilization in leachate prior to dechlorination or nitro-group reduction, biodegradation and complexation.

Phenolics and Nitroaromatics(DCP, NP, NB)

Volatilization and sorptive matrix capture prior to partial reductive dechlorination.Chlorinated Benzenes(HCB, TCB, DCB)

Volatilization and mobilization in gas and leachate prior to abiotic and biotic reductivedehalogenation under methanogenic, methanotrophic, sulfate reducing and denitrifying conditions.

Organic Compounds**

Halogenated Aliphatics(PCE, TCE, DBM)

Dominant Attenuation Mechanisms during Landfill Stabilization PhasesConstituents

TODAY AND BEYOND

• Needs Assessment and Resolution– Scientific and technical inquiry/discovery/application

• Rational Management and Oversight– Checks and balances

• Stakeholder Harmonization– Perspective and participation

• Sustainability– Goals achievement

Bioreactor Landfill with Leachate and Gas Treatment Options

LANDFILL

GAS TREATMENT

PIPELINEQUALITY

ON-LINEFLARING

IN SITUVS.

EXTERNAL TREATMENTLEACHATE RECYCLE

BIOLOGICAL TREATMENT

ACTIVATED SLUDGE ANAEROBIC FILTERAERATED LAGOON ANAEROBIC CONTACTSTABILIZATION POND NITRIFICATIONTRICKLING FILTER DENITRIFICATION

EXTERNAL TREATMENT

COMBINED TREATMENT

PHYSICAL/CHEMICAL TREATMENT

PRECIPITATION/COAGULATIONCHEMICAL OXIDATION/REDUCTIONADSORPTIONION EXCHANGEREVERSE OSMOSISDISINFECTION

DISCHARGE OPTIONPOTW LAND APPLICATION

DIRECT USE

Stabilization Time, Days

Gas

Com

posi

tion,

% b

y Vo

lum

e0

20

40

60

80

100

CO

D, T

VA, g

/L

0

10

20

30

40

50

Incr

emen

tal G

as P

rodu

ctio

n, m

3

0.0

0.2

0.4

0.6

0.8

1.0

pH

5

6

7

8

Amm

onia

, mg/

L

0

1000

2000

3000

OR

P, m

V Ec

-150

-100

-50

0

50

100

150

pH

Ammonia

ORP

N2

COD

O2

TVA

H2

CH4

CO2

Incremental Gas Production

O2

Phase IInitial

Phase IITransition

Phase IIIAcid

Formation

Phase IVMethane Fermentation

Phase VFinal

Maturation

0 200 400 600

Sulfi

de, m

g/L

0510152025

H2S

Operational features of a bioreactor landfill

External LeachateRecirculation Pump Station

Final Cover

LeachateRecirculationField

DedicatedTreatment Zone

Gravel PackedTrench withPerforated Pipe

Isolation Berm

CompartmentLimit

Primary LeachateCollection System

Leak Detection System

Leachate Recharge/Gas Extraction Wells

Gas Flare

Leachate Storage

ExternalTreatmentPlant

Groundwater MonitoringWell

Internal Primary LeachatePump Station

Internal Leak DetectionMonitoring Well

External PumpStation

Stormw

ater

GasRecovery