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Operating Landfills as Bioreactors to Decompose and Stabilize Solid Waste Timothy Townsend, PhD, PE Associate Professor Dept. of Environmental Engineering.

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Presentation on theme: "Operating Landfills as Bioreactors to Decompose and Stabilize Solid Waste Timothy Townsend, PhD, PE Associate Professor Dept. of Environmental Engineering."— Presentation transcript:

1 Operating Landfills as Bioreactors to Decompose and Stabilize Solid Waste Timothy Townsend, PhD, PE Associate Professor Dept. of Environmental Engineering Sciences University of Florida

2 Topics Bioreactor landfill fundamentals Application to Lined Landfills –Methods –Challenges –Aerobic bioreactors –Case studies in Florida Application to Unlined Landfills

3 Bioreactor Landfill Fundamentals Definition A sanitary landfill operated for the purpose of rapid stabilization of the decomposable organic waste constituents by purposeful control of biological processes

4 Bioreactor Landfill Fundamentals Potential Benefits Increase disposal capacity Provides flexibility in leachate management Enhances feasibility of landfill gas to energy projects May possibly reduce long term costs Promotes more sustainable waste management

5 Bioreactor Landfill Fundamentals Methods Create conditions for waste degrading organisms to thrive Most typically performed by increasing moisture content –Leachate recirculation –Water addition The addition of air is being explored

6 Traditional Landfill Goal: Keep Liquids Out Buried Waste (little decomposition) Cap Liner and Leachate Collection system CH 4, CO 2 Leachate to Treatment Plant

7 Bioreactor Landfill Goal: Add Liquids Buried Waste (rapid decomposition) Cap Liner and Leachate Collection System Leachate to Treatment Plant CH 4, CO 2 Leachate Recirculation Schematic Shows Anaerobic Operation

8 Bioreactor Landfill Goal: Rapid Stabilization Buried Waste (rapid decomposition) Cap Liner and Leachate Collection System Leachate to Treatment Plant CH 4, CO 2 Leachate Recirculation Schematic Shows Anaerobic Operation

9 Bioreactor Landfill Goal: Rapid Stabilization Buried Waste (rapid decomposition) Cap Liner and Leachate Collection System Leachate to Treatment Plant CH 4, CO 2 Leachate Recirculation Schematic Shows Anaerobic Operation

10 Bioreactor Landfill Goal: Rapid Stabilization Buried Waste (rapid decomposition) Cap Liner and Leachate Collection System Leachate to Treatment Plant CH 4, CO 2 Leachate Recirculation Schematic Shows Anaerobic Operation

11 Gas Production Bioreactor Landfill Conventional Landfill

12 Application to Lined Landfills Conventional practice of this technology in the US is at lined landfills. Leachate is recirculated back to the waste. Water or other liquids may be added as well.

13 Application to Lined Landfills Methods of leachate recirculation –Spray irrigation –Surface ponding –Vertical wells –Horizontal trenches

14 Application to Lined Landfills Challenges –Getting the moisture to the right place –Waste heterogeneity –Monitoring progress and determining completion –Collecting gas –Avoiding problems caused by too much moistures –Slope stability

15 Aerobic Bioreactors Relatively new technique Air is added to the waste Aerobic stabilization in much quicker Concerns –Fire potential –Explosive gas mixtures –Air emissions –Cost

16 Bioreactor Landfill Research in Florida Research is being conducted at several sites Discussion follows on two particular sites –Alachua County Southwest Landfill –New River Regional Landfill

17 Alachua County Southwest Landfill Line landfill Leachate recirculation started in 1990 Currently closed and capped. Collected gas is converted to energy

18 Early Surface Infiltration Systems

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22 Horizontal Trenches for Leachate Recirculation

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24 Samples of Waste Were Collected and Analyzed

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26 Current Leachate Recirculation: Under the Cap

27 Gas is converted to “green” energy

28 New River Regional Landfill Lined Landfill Manages waste from several North Florida Counties (approximately 800 tons per day)

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31 Bioreactor Features Vertical Injection Wells (small diameter cluster wells) Half of the landfill currently is set up for air injection if desired Exposed Geomembrane Cap Gas collection from the EGC and the leachate collection system Moisture and temperature instrumentation Segregated leachate collection system

32 Top of Landfill Top of Sand Drainage Blanket 10 ft Vertical Injection Cluster Wells Use multiple small diameter wells.

33 Installation of Small Diameter Recirculation Wells: Open Flight Auger

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36 Grading Around Wells

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39 Instrumented Well Field

40 Vertical Injection Well Clusters Leachate Distribution Manifold

41 Vertical Injection Well Clusters 134 wells in 45 clusters

42 Vertical Injection Well Clusters Leachate Distribution Manifold Air Injection Manifold

43 NRRL Gas Extraction System Gas is collected from the horizontal trenches underneath the exposed geomembrane cap Geomembrane Cap Subsurface Collector

44 Deploying Geomembrane

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46 Gas Extraction Wells

47 Gas Extraction Manifold

48 Blower Flare Station

49 Candle-Stick Flare Two Positive Displacement Air Blowers Three Centrifugal Gas Extractors

50 Resistivity Probe For Moisture Measurements

51 Vertical Injection Well Clusters

52 Instrumentation Cluster

53 Instrumentation in Place 332 thermocouples 138 resistivity sensors 45,000 ft of thermocouple wire 20,000 ft of resistivity wire

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56 High Temperature (degree C) Low Temperature (degree C) North Surface of Bioreactor 20 feet deep 60 feet deep 40 feet deep Temperature distribution inside NRRL Bioreactor, 12/18/02

57 High Resistivity (Low Moisture) Low Resistivity (High Moisture) North Surface of Bioreactor 20 feet deep 60 feet deep 40 feet deep Resistivity distribution inside NRRL Bioreactor, 12/18/02

58 Segregated Leachate Collection at Manholes Leachate collection pipes were retrofitted with weir boxes to measure flow and leachate quality from different areas of the landfill

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61 Current Status Nearly 3 million gallons of leachate has been recirculated Extensive research is being conducted on the hydraulics of the landfill, the use of in- situ sensors, gas emissions, and other bioreactor operations issues Aerobic technology is being explored

62 Application to Unlined Landfills Not a common practice Offers a potential remediation technique Aerobic stabilization has been proposed for older unlined landfills Issues: –Hydraulic control –Gas emissions

63 For More Information Florida Center for Solid and Hazardous Waste Management John Schert:


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