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Lecture 18

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					                                     Solid Waste Landfills

                               • Why the concern?
Solid and Hazardous Waste        – Disease Vectors
       Management                – Odors
                                 – Fires
        Lecture 18
                               • Sanitary Landfill
       Land Disposal


             Lecture 18                        Lecture 18
            Land Disposal                     Land Disposal




                              Modern Landfills are Engineered
     Modern Concerns
                                       Structures

     • Leachate

                            • Designed to Contain Leachate and
     • Landfill Gas
                              Minimize Release of Pollutants from the
                              Landfill




             Lecture 18                        Lecture 18
            Land Disposal                     Land Disposal




                                                                        1
       Some Landfills are Lined                     Liner Materials

• Liner -- A low permeability barrier     • Compacted Soil (clay)
  system
• Lined Landfills:                        • Geomembrane (plastic)
  – Subtitle D (MSW)
  – Subtitle C (Hazardous Waste)
  – Some C&D and Industrial



                   Lecture 18                              Lecture 18
                  Land Disposal                           Land Disposal




        Types of Liner Systems                   Single Liner System

           • Single                     • One liner consisting of compacted soil
           • Composite                    or geomembrane
           • Double




                   Lecture 18                              Lecture 18
                  Land Disposal                           Land Disposal




                                                                                   2
           Composite Liner                                  Double Liner

• A single liner consisting of compacted       • A liner system with low permeability
  soil and geomembrane in intimate               barrier layers with a leak detection
  contact                                        system layer in between. The upper
                                                 and lower components are either
                                                 compacted soil, geomembrane, or
                                                 composite.


                   Lecture 18                                       Lecture 18
                  Land Disposal                                    Land Disposal




     Leachate Collection System                 Single Geomembrane Liner System

                                             Leachate
• If leachate flow is intercepted or                              Waste
  impeded by a liner, then it should be
  removed from the landfill by use of a
                                                                                    Leachate
  leachate collection system. A leachate                                            Collection
  collection system is a high-permeability                                          System
  layer designed to transmit leachate from
  the liner.                                        Geomembrane

                                                              Existing Soil
                   Lecture 18                                       Lecture 18
                  Land Disposal                                    Land Disposal




                                                                                                 3
       Single Composite Liner System                                Double Liner System
                                                                                                           Primary
 Leachate                                              Leachate                                            Leachate
                        Waste                                             Waste                            Collection
                                                                                                           System


                                         Leachate                                                 Secondary Leachate
                                         Collection                                               Collection System
                                         System

Geomembrane                                           Geomembrane
                  Geomembrane                                          Geomembrane


                   Existing Soil
                       Lecture 18                                       Existing Soil
                                                                            Lecture 18
                         Land Disposal                                     Land Disposal




        How Do You Determine Liner                     RCRA Subtitle D MSW Landfill Requirements
             Requirements?

   • Regulation
                                                                                            Maintain less than 1 ft
      – 40 CFR 258                                                                             head on liner.
      – MSW Landfills
                                                                                           30-mil (60-mil HDPE)
                                                                                              Geomembrane.
      – 40 CFR 624
                                                                                                 2-ft Soil Liner:
      – Hazardous Waste
                                                                                            Hydraulic conductivity not
                                                                                             more than 1E-7 cm/sec.


                          Lecture 18                                        Lecture 18
                         Land Disposal                                     Land Disposal




                                                                                                                         4
RCRA Subtitle C MSW Landfill Requirements
                                                                        Florida MSW Requirements

                                                                 • Composite or Double Geomembrane
                                    Maintain less than 1 ft
                                       head on liner.            • Can Demonstrate Equivalency
                                     Geomembrane.
LDS
                                     Geomembrane.

                                         3-ft Soil Liner:
                                    Hydraulic conductivity not
                                     more than 1E-7 cm/sec.


                     Lecture 18                                                      Lecture 18
                    Land Disposal                                                   Land Disposal




      Types of Geomembrane Materials                                 What Controls Head on the Liner?

              •   HDPE                                           •   Liner Slope
              •   PVC                                            •   Pipe Spacing
              •   VLDPE                                          •   LCS Hydraulic Conductivity
              •   PP                                             •   Impingement Rate




                     Lecture 18                                                      Lecture 18
                    Land Disposal                                                   Land Disposal




                                                                                                        5
       What is a Geonet?                      What is a Geotextile?




               Lecture 18                                 Lecture 18
              Land Disposal                              Land Disposal




                                     How do you Remove Leachate from
What is a Geosynthetic Clay Liner?
                                               the Landfill?

                                     • Drain as much as you can by gravity
                                       (liner system and pipes)
                                     • Pump from low points
                                       – Penetration through the liner
                                       – Pumps inside landfill




               Lecture 18                                 Lecture 18
              Land Disposal                              Land Disposal




                                                                             6
    How do you Predict Leachate
                                                              HELP
           Generation?
                                            • A Water Balance Model
• You must estimate how much leachate
  is generated to design your landfill.                   P                       ET
                                                                                       R
• HELP --
  Hydrologic Evaluation of Landfill
  Performance


                                                                                       Q
                   Lecture 18                                  Lecture 18
                  Land Disposal                               Land Disposal   L




      Notes about HELP Model                              Leachate

• Must assume an area and a depth           • Can contain many compounds
  (therefore not good for an open,
  operating landfill)
• Many ways to manipulate
• Hydraulic conductivity of waste to high



                   Lecture 18                                  Lecture 18
                  Land Disposal                               Land Disposal




                                                                                           7
 Comparison of Florida Leachates to
                                                            How is Leachate Managed?
        National Database
    Parameter Fl Leachate, BFI Leachate, Statistical   • On-Site WWTP
                 mg/L          mg/L      Difference?
   BOD             197         3740          Yes         (must discharge effluent)
   COD            1427         5280          Yes       • Haul to Off-Site POTW
   Ammonia         272          277          No
   Sulfate          81          211          Yes       • Pretreat On-Site and Haul Off-Site
   Chloride        678         1830          Yes
   pH              7.4          6.4          Yes
                                                       • Pipeline
   Manganese        77          207          Yes       • Evaporate
   Zinc            306          260          No
                                                       • Leachate Recirculation
                     Lecture 18                                          Lecture 18
                    Land Disposal                                       Land Disposal




                Landfill Gas                                   Landfill Gas Contains

• What is Landfill Gas?                                • Methane
                                                       • Carbon Dioxide
                                                       • Water Vapor
C6 H10 O5 + H2 O → 3 CH4 + 3 CO2                       • Hydrogen Sulfide
                                                       • NMOC (nonmethane organic
                                                         compounds)
                                                       • heavy metals??
                     Lecture 18                                          Lecture 18
                    Land Disposal                                       Land Disposal




                                                                                              8
      Why Bother with Landfill Gas?                  How is Gas Collected?

•   Odor                                    • Typically use vertical wells.
•   Toxics                                  • Installed after landfill has reached final
•   Greenhouse Gas                            grade.
•   Explosive Gas                           • Use an auger.


• Potential Energy Source

                    Lecture 18                                  Lecture 18
                   Land Disposal                               Land Disposal




    What is the Driving Force for Gas to
                                                               Wells
             Leave the Landfill?

• Pressure                                  • Passive Wells (wells open to
• Without any wells, gas will find way to     atmosphere)
  surface (or bottom)                       • Active Wells (wells connected to a gas
• Wells provide path of escape (create        extraction system).
  pressure gradient)



                    Lecture 18                                  Lecture 18
                   Land Disposal                               Land Disposal




                                                                                           9
                                                                                    LFG Collection From Operating Landfills

                                                                                                                                          Sub-Cap Collector
                                                                                         Horizontal
                                                                                         Collectors               o
                                                                                                                                      o

                                                                                                              o
                                                                                                                             o
                                                                                                                                           o
                                                                                                          o

                                                                                                      o




                                                                                    Leachate Collection System - LFG Collector Network
                                        Lecture 18                                                                     Lecture 18
                                       Land Disposal                                                                  Land Disposal




                                    LFG Generation Curves
                                                                                               What is Condensate?
                   25,000,000


                                                   Half-Life = 1.35 yr
Cubic meters LFG




                   20,000,000


                   15,000,000
                                                       Half-Life = 3.68 yr

                   10,000,000

                                                           Half-Life = 20 yr
                    5,000,000


                            0
                                0      10         20          30      40       50


                                        Lecture 18
                                                   Year                                                                Lecture 18
                                       Land Disposal                                                                  Land Disposal




                                                                                                                                                              10
            Gas to Energy?




                  Lecture 18                                    Lecture 18
                 Land Disposal                                 Land Disposal




            Landfill Closure                               Cap System

• When you obtain a permit for a            • Very similar to a landfill, but designed to
  landfill,you must demonstrate financial     keep water out instead of keeping
  assurance.                                  leachate in.
• Must show that you have funds to close
  the landfill and watch for 30 years of
  post closure care.


                  Lecture 18                                    Lecture 18
                 Land Disposal                                 Land Disposal




                                                                                            11
 What do you do the the landfill after
             closure?

• Watch forever?

• Golf course, park?

• Mine?



                    Lecture 18
                   Land Disposal




                                         12

				
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