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
CH4, CO2
Cap
Buried Waste (little decomposition)
Liner and Leachate Collection system
Leachate to Treatment Plant

7. Bioreactor Landfill Goal: Add Liquids
Leachate Recirculation
CH4, CO2
Cap
Buried Waste (rapid decomposition)
Liner and Leachate Collection System
Leachate to Treatment Plant
Schematic Shows Anaerobic Operation

8. Bioreactor Landfill Goal: Rapid Stabilization
Leachate Recirculation
CH4, CO2
Cap
Buried Waste (rapid decomposition)
Liner and Leachate Collection System
Leachate to Treatment Plant
Schematic Shows Anaerobic Operation

9. Bioreactor Landfill Goal: Rapid Stabilization
Leachate Recirculation
CH4, CO2
Cap
Buried Waste (rapid decomposition)
Liner and Leachate Collection System
Leachate to Treatment Plant
Schematic Shows Anaerobic Operation

10. Bioreactor Landfill Goal: Rapid Stabilization
Leachate Recirculation
CH4, CO2
Cap
Buried Waste (rapid decomposition)
Liner and Leachate Collection System
Leachate to Treatment Plant
Schematic Shows Anaerobic Operation

11. Bioreactor Landfill
Gas Production
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

19. Early Surface Infiltration Systems

20. Early Surface Infiltration Systems

21. Early Surface Infiltration Systems

22. Horizontal Trenches for Leachate Recirculation

23. Horizontal Trenches for Leachate Recirculation

24. Samples of Waste Were Collected and Analyzed

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)

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

33. Installation of Small Diameter Recirculation Wells: Open Flight Auger

36. Grading Around Wells

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

45. Deploying Geomembrane

46. Gas Extraction Wells

47. Gas Extraction Manifold

48. Blower Flare Station

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

50. Resistivity Probe For Moisture Measurements

51. Vertical Injection Well Clusters

52. Vertical Injection Well Clusters
Instrumentation Cluster

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

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

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

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

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: