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Introduction to disposal part 2 engineering barriers in landfill

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Rehab O. Abdel Rahman
Rehab O. Abdel Rahman

This document discusses the key components and design considerations for landfill liner systems and leachate and gas management. It outlines that liners should have low hydraulic conductivity, adequate shear strength, and minimal shrinkage potential. Common liner materials include clay, soil admixes, polymers, and membranes. Effective leachate and gas collection systems are also needed, along with monitoring and closure/post-closure plans.

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Dr. Rehab O. Abdel Rahman Associate Professor, AEAE alaarehab@yahoo.com
Liner selection Leachate collection system Gas collection system Monitoring Closure and post closure plan
Design Objectives Low hydraulic conductivity to minimize leakage (K 10-7 cm/sec) Adequate shear strength to maintain liner stability under landfill weight and loads from vehicular movement Minimal shrinkage potential to minimize desiccation cracking Chemical stability for reactions with the waste or leachate
Materials Soils, such as benotnite, compacted clay Admixes such as asphalte concrete, asphalte membrane, soil cement Polymer such as geotextile, geomembrane Organic and inorganic bases and hydrocarbon pollutant will eliminate some polymer and soil asphalt Limited Budget use soil or soil cement or asphalt liner, some polymer Membrane (asphalte, polymer ) are medium cost
Introduction to disposal part 2 engineering barriers in landfill
Clay advantage Low cost High cation exchange capacity Resist leachate migration Low Ks, due to Small size Compact soil fabric Good geomechnical properties, i.e. Toughness, Dilatancy, Plactiticty Disadvantage clay Dissolution may occur due to the acidity of leachate
Types of liner Single Single composite Double composite
Introduction to disposal part 2 engineering barriers in landfill
Located at the bottom of the landfill above liner 1) Drainage layer Highly permeable layer to ease lateral drainage of leachate Its thickness > 30 cm Permeability 0.001 cm/sec 2) Sloped terrace To increase the potential to lateral migration of leachate (2% slope)
3) Perforated pipes To collect and drain the leachate 10 cm D HDPE or PVC pipes with perforation of 1 cm in the upper three quarters 4) Filter layer An inverted filter used to prevent clogging of pipes due to sand ingression from drainage layer 5) Sump well Used to pump out the leachate collected at the bottom of the landfill
After collection, leachate is treated using Biological treatment (aerobic- anaerobic) Physical and chemical treatment (flocculation sedimentation-filtration- sorption)
Leachate leakage may occur from the bases or sides of landfill due to 1) Joint failure or puncture of geo-membrane liner 2) Cracks in the clay liner 3) Excessive pressure build up in the landfill How to calculate leachate flow in disposal Use darcy law Q=KiA 1) Q amount of leachate (m3/d) 2) K hydraulic conductivity (m/d) 3) i hydraulic gradient (h1-h2)/l 4) A area of landfill (m2)
Gases generated in landfill Methane Carbon dioxide Nitrogen oxygen Hydrogen Hydrogen sulfide Carbon monoxide
Potential environmental impact of landfill gases Explosion Asphyxiation, Vegetation damage Water pollution Corrosion Nuisance Methane is lighter than air Carbon dioxide is heavier than air
Factors affect gas generation Moisture content Waste type Nutrient content Specific weight Ph Temperature Particle size
to prevent migration of gas to the nearby areas it as an energy resource, Components of Gas Collection System Gas wells placed within the wastes Header system to connect the well to the gas Pumping unit Gas purification system Energy recovery Plant
Introduction to disposal part 2 engineering barriers in landfill
Double liner System-at the base and sides of the landfill to prevent migration of leachate to the surroundings Leachate Collection and Treatment Facility-to collect leachate from the base of the landfill for treatment to meet regulatory standards Gas Collection and Treatment Facility-to collect gas emanating from the landfill and to treat Final Cover-at the top of landfill to prevent infiltration of water into the landfill and to support vegetation.
Surface drainage System-to collect and divert all surface runoff from the landfill Environmental Monitoring Plan-for periodic monitoring of environmental quality of air, surface water, groundwater, vadoze zone. Closure and Post-closure Plan details of activities to be undertaken to close a landfill site once the filling operation has been completed and for monitoring and maintenance of the completed landfill.
Introduction to disposal part 2 engineering barriers in landfill

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Introduction to disposal part 2 engineering barriers in landfill

  • 1. Dr. Rehab O. Abdel Rahman Associate Professor, AEAE alaarehab@yahoo.com
  • 2. Liner selection Leachate collection system Gas collection system Monitoring Closure and post closure plan
  • 3. Design Objectives Low hydraulic conductivity to minimize leakage (K 10-7 cm/sec) Adequate shear strength to maintain liner stability under landfill weight and loads from vehicular movement Minimal shrinkage potential to minimize desiccation cracking Chemical stability for reactions with the waste or leachate
  • 4. Materials Soils, such as benotnite, compacted clay Admixes such as asphalte concrete, asphalte membrane, soil cement Polymer such as geotextile, geomembrane Organic and inorganic bases and hydrocarbon pollutant will eliminate some polymer and soil asphalt Limited Budget use soil or soil cement or asphalt liner, some polymer Membrane (asphalte, polymer ) are medium cost
  • 6. Clay advantage Low cost High cation exchange capacity Resist leachate migration Low Ks, due to Small size Compact soil fabric Good geomechnical properties, i.e. Toughness, Dilatancy, Plactiticty Disadvantage clay Dissolution may occur due to the acidity of leachate
  • 7. Types of liner Single Single composite Double composite
  • 9. Located at the bottom of the landfill above liner 1) Drainage layer Highly permeable layer to ease lateral drainage of leachate Its thickness > 30 cm Permeability 0.001 cm/sec 2) Sloped terrace To increase the potential to lateral migration of leachate (2% slope)
  • 10. 3) Perforated pipes To collect and drain the leachate 10 cm D HDPE or PVC pipes with perforation of 1 cm in the upper three quarters 4) Filter layer An inverted filter used to prevent clogging of pipes due to sand ingression from drainage layer 5) Sump well Used to pump out the leachate collected at the bottom of the landfill
  • 11. After collection, leachate is treated using Biological treatment (aerobic- anaerobic) Physical and chemical treatment (flocculation sedimentation-filtration- sorption)
  • 12. Leachate leakage may occur from the bases or sides of landfill due to 1) Joint failure or puncture of geo-membrane liner 2) Cracks in the clay liner 3) Excessive pressure build up in the landfill How to calculate leachate flow in disposal Use darcy law Q=KiA 1) Q amount of leachate (m3/d) 2) K hydraulic conductivity (m/d) 3) i hydraulic gradient (h1-h2)/l 4) A area of landfill (m2)
  • 13. Gases generated in landfill Methane Carbon dioxide Nitrogen oxygen Hydrogen Hydrogen sulfide Carbon monoxide
  • 14. Potential environmental impact of landfill gases Explosion Asphyxiation, Vegetation damage Water pollution Corrosion Nuisance Methane is lighter than air Carbon dioxide is heavier than air
  • 15. Factors affect gas generation Moisture content Waste type Nutrient content Specific weight Ph Temperature Particle size
  • 16. to prevent migration of gas to the nearby areas it as an energy resource, Components of Gas Collection System Gas wells placed within the wastes Header system to connect the well to the gas Pumping unit Gas purification system Energy recovery Plant
  • 18. Double liner System-at the base and sides of the landfill to prevent migration of leachate to the surroundings Leachate Collection and Treatment Facility-to collect leachate from the base of the landfill for treatment to meet regulatory standards Gas Collection and Treatment Facility-to collect gas emanating from the landfill and to treat Final Cover-at the top of landfill to prevent infiltration of water into the landfill and to support vegetation.
  • 19. Surface drainage System-to collect and divert all surface runoff from the landfill Environmental Monitoring Plan-for periodic monitoring of environmental quality of air, surface water, groundwater, vadoze zone. Closure and Post-closure Plan details of activities to be undertaken to close a landfill site once the filling operation has been completed and for monitoring and maintenance of the completed landfill.

Editor's Notes

  • #6: Chapter 11.3 Clay Liners and Waste Disposal, Handbook of Clay Science Edited by F. Bergaya, B.K.G. Theng and G. Lagaly Developments in Clay Science, Vol. 1 r 2006 Published by Elsevier Ltd