Operating Landfills as Bioreactors to Decompose and Stabilize Solid Waste

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 LandfillGoal Keep Liquids Out
CH4, CO2
Cap
Buried Waste(little decomposition)
Leachate toTreatment Plant
Liner and LeachateCollection system
7
Bioreactor LandfillGoal Add Liquids
LeachateRecirculation
CH4, CO2
Cap
Buried Waste(rapid decomposition)
Leachate toTreatment Plant
Liner and LeachateCollection System
Schematic Shows Anaerobic Operation
8
Bioreactor LandfillGoal Rapid Stabilization
LeachateRecirculation
CH4, CO2
Cap
Buried Waste(rapid decomposition)
Leachate toTreatment Plant
Liner and LeachateCollection System
Schematic Shows Anaerobic Operation
9
Bioreactor LandfillGoal Rapid Stabilization
LeachateRecirculation
CH4, CO2
Cap
Buried Waste(rapid decomposition)
Leachate toTreatment Plant
Liner and LeachateCollection System
Schematic Shows Anaerobic Operation
10
Bioreactor LandfillGoal Rapid Stabilization
LeachateRecirculation
CH4, CO2
Cap
Buried Waste(rapid decomposition)
Leachate toTreatment Plant
Liner and LeachateCollection System
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
25
(No Transcript)
26
Current Leachate RecirculationUnder 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)

29
(No Transcript)
30
(No Transcript)
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
Vertical Injection Cluster Wells Use multiple
smalldiameter wells.
10 ft
Top of Sand DrainageBlanket
33
Installation of Small DiameterRecirculation
WellsOpen Flight Auger
34
(No Transcript)
35
(No Transcript)
36
Grading Around Wells
37
(No Transcript)
38
(No Transcript)
39
InstrumentedWell 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
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

54
(No Transcript)
55
(No Transcript)
56
Temperature distribution inside NRRL Bioreactor,
12/18/02
Surface of Bioreactor
High Temperature (degree C)
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)
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

59
(No Transcript)
60
(No Transcript)
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

• Email ttown_at_ufl.edu
• Florida Center for Solid and Hazardous Waste
  Management
• John Schert jschert_at_ufl.edu
• www.bioreactor.org
• www.floridacenter.org