Aerobic vs. Anaerobic Bioreactor Landfill Case Study: the New

River Regional Landfill

Presented at SWANA’s 6th Annual Landfill Symposia

San Diego, CAJune 18-20, 2001

Debra R. Reinhart, PhDTimothy Townsend, PhD

View of drill rig from the landfill’s entrance road.Drill Rig Panorama

Presentation Overview

• Brief overview of NRRL bioreactor project

• Flammability issues• Cost issues• Moisture balance issues• Waste degradation issues• Process control impacts

Project Location

Cell 3Cells 1 & 2

Bioreactor

Bioreactor Components

• Leachate Collection System Modifications

• Leachate/Air Injection• Gas Collection• Geomembrane Cap

• Three Wells

• Spacing 3-5 ft

• Maintain 10 ft distancefrom top of sand drainage layer to bottom of the well

Top of Landfill

Top of Sand DrainageBlanket

10 ft

Cluster Well Sketch

Bioreactor Gas Extraction

Cell 1Cell 2

GeomembraneCap

Gas

Monitoring

• Leachate• Landfill Gas• Waste Properties• Settlement

Instrumentation

• Head on Liner• Leachate Flow• Landfill Temperature• Landfill Moisture Content

Moisture Sensors

New River Regional Landfill Bioreactor Demonstration ProjectCross Section on Injection Cluster Wells C8 (x=600)

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Landfill Surface Well Bottom Safety Zone Bottom Liner

10 ft

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CJ8 CH8 CF8CD8

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New River Regional Landfill Bioreactor Project

New River Regional LandfillLocation: Union County, Florida

Monitoring WellInjection Well

Bioreactor Landfill BoundaryAccess Road

Legend General Temperatute SketchInjection Wells Sheet Nº

1/4

File: temp def sketch.srf Date: 05/30/01Scale: 1:125Units:English

Scale: 1:50Units:English

New River Regional Landfill Bioreactor Project

New River Regional LandfillLocation: Union County, Florida

Monitoring WellInjection Well

Bioreactor Landfill BoundaryAccess Road

Legend Temperature MapInjection Wells B (~40-50 ft deep) Sheet Nº

3/4

File: Temperature.srf Date: 05/30/01

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New River Regional LandfillTemperature Profiles

Monitoring Probe

InstrumentationPackageClay

Instrumentation and Injection Wells

Anaerobic vs. Aerobic Landfilling

• Flammability• Moisture Balance• Process Control• Degradation Pathways• Waste Degradation• Costs

02468

10121416182022

0 5 10 15 20 25% Methane

% O

xyge

nMixtures that can

not be formed

ExplosiveRange

Not capable offorming flammablemixtures with air

Capable of forming flammablemixtures with air (contains too

much methane to be in explosive range)

02468

10121416182022

0 5 10 15 20 25 30 35 40 45 50 55% Methane

% O

xyge

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Arid Region Landfill

Air

Aerobic Landfill

Anaerobic Landfill

Moisture Issues: Anaerobic Decomposition

→+ OHOHC 25106 24 33 COCH +

Moisture Issues: Aerobic Decomposition

→+ 25106 6OOHC OHCO 22 56 +

Aerobic Landfill

Moisture Balance

Moisture,gpm/acre

Aerobic Anaerobic

Loss/Gain –Biodegradation

0.51 0.24

Removed inExhaust Gas

1.16 0.21

Required Input 0.65 0.45

Measure GasConcentration

Plot data Immediate-ly stop airinjection

Gas inexplo-sive

range.

Gasoutside ofexplosive

MonitoringPoint inAnaerobic?

MonitoringPoint inAerobic

O2 >2 %CH4 2 %

ConsiderIncr. Flow

Decrease Air

YesNo

O2 10%

Control Diagram

MeasureTemperature

T < 140 °F

T > 140 °FT < 160 °F

T > 160 °FT < 170 °F

T > 170 °F

Possible concern. Check gas concentrations.If anaerobic → Add leachateIf aerobic → Reduce air flow rate. Track the rate oftemperature increase of this area. If a rate of 1°F perday (weekly average) is exceeded, stop air injectionand add leachate/water.

Temperature may be below optimum. Investigateand revise operations as desired. Not a safety hazard.

Optimum conditions. Operate and monitor asscheduled.

Condition of concern. Stop air injection. Addleachate at permitted amount only, or request thatDEP allows more liquid volume injection.

Waste Degradation

• Different pathways– Some compounds are recalcitrant under aerobic

conditions and degrade under anaerobic conditions and vice versa

• Energy yields– Aerobic reactions yield more energy, this can lead

to elevated temperatures under low MC• Byproduct formation

– H2S– Methane

Waste Stabilization

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Time, years

CO

D, g

/L

Leachate COD Reduction Half-Lives

Scale OperatingRegime

COD Half-Life,Days

Laboratory Anaerobic Wet 26 – 157Laboratory Anaerobic Conventional 150 – 1369Laboratory Semi-aerobic Wet 24Laboratory Semi-aerobic Conventional 26

Pilot Anaerobic Wet 117Pilot Anaerobic Conventional 99Full Anaerobic Wet 285 – 383Full Anaerobic Conventional 3650

Cost Issues

Aerobic– Energy

Requirements– Loss of methane– Potential GHG

emission offset credits

– Additional moisture requirements

Anaerobic– Gas

collection/treatment– Additional leachate

treatment

Energy Considerations –Aerobic Landfill

• Blowers– Push air through landfill– 4.75 x volume of anaerobic gas production– NRRL Aerobic Energy Requirements 12 x

Anaerobic

Conclusions• Power requirements are twelve times higher for an

aerobic bioreactor as compared to the anaerobicbioreactor.

• Aerobic bioreactor moisture requirements are 29%higher.

• Due to the presence of diluent gases in aerobicbioreactor gases, flammable conditions are unlikelyto develop, particularly if process conditions ensurelow oxygen levels.

• The addition of water and air significantlyaccelerations the rate of reduction of organic materialin leachate.

• Oxygen content and internal temperature are criticalcontrol components for aerobic and anaerobicbioreactors

Schedule (Estimated)

• Permit Award: December 2000• Instrumentation Installation: Spring

2001• Bioreactor Construction: Fall 2001• Begin Bioreactor Operation: Late

2001

Aerobic vs. Anaerobic Bioreactor Landfill Case Study: the New River Regional LandfillDrill Rig PanoramaPresentation OverviewSlide Number 4Slide Number 5Slide Number 6Bioreactor ComponentsCluster Well SketchBioreactor Gas ExtractionGeomembrane�CapSlide Number 11MonitoringInstrumentationMoisture SensorsSlide Number 15Slide Number 16Slide Number 17Slide Number 18Monitoring ProbeInstrumentation and Injection WellsAnaerobic vs. Aerobic LandfillingSlide Number 22Slide Number 23Moisture Issues: Anaerobic DecompositionMoisture Issues: Aerobic DecompositionAerobic Landfill Moisture BalanceSlide Number 28Slide Number 29Waste Degradation Waste StabilizationLeachate COD Reduction Half-Lives Cost IssuesEnergy Considerations – Aerobic LandfillConclusionsSchedule (Estimated)