Lecture 1 Landfill.pptx , and parameters

complete description of landfill design

1. Lecture 1 Landfill

2. History of landfills Open dumps sanitary landfill (in past, only covered at the end of day) sanitary landfill (solid waste management unit) bioreactor landfill Secure landfill (hazardous)

3. Landfill condition Landfilling is the oldest and most widely practiced waste disposal option. Modern landfill: engineered Suitable wastes for landfill landfilling include biodegradable wastes, aqueous liquids in limited amounts, inert wastes, and certain special wastes that would not pose toxic threats. Wastes not included are volatile liquids or solvents, wastes that would introduce unacceptable contamination into the leachate, and wastes that would interfere with the biological processes in a landfill site.

4. Advantage and Disadvantage It costs less than other disposal options A wide variety of wastes are suitable for landfill It frequently offers the only final disposal route for residues arising from end-of-pipe treatment technologies and other waste management options, such as incineration Landfill gas can be collected and utilized for heat and as a low-polluting fuel for energy generation  Landfills Support Jobs and Local Business Landfills are Partially Responsible For Climate Change Methane Lights up Easily Contaminate Soil and Water  Landfills Affect Wildlife Accidents Can Happen Landfills Affect Human Health Older sites, constructed before the impacts of leachate and landfill gas were realized, are now sources of pollution with uncontrolled leakages

5. Defining the terms Landfill : physical facility Landfilling includes: Monitoring of incoming waste Placement an compaction of the waste Installation of landfill environmental monitoring and control facilities Cell: volume of material placed in a landfill during one operating period Cell = SW deposited + daily cover (6-12” of native soil or composting) Lift: complete layer of cells over the active area of the landfill. Landfill = Series of lifts Bench: is a terrace when the height of the landfill exceeds 50 to 75 ft

6. Defining the terms Final lift: includes the cover layer Cover layer includes multiple layers of soils/ geomembrane material Leachate: liquid collected at the bottom of the landfill Landfill gas: mixture of gases found in the landfill Landfill liners: used to line the bottom area and below grade sides of a landfill Landfill control facility: includes liners, landfill leachate collection and extraction system Environmental monitoring: Monitor of gas, ground water, movement of gas and leachate Landfill closure: steps must be taken to close and secure a landfill Post closure: long term monitoring of the landfill

7. Preparation of the site for landfilling Rerouting of drainage to keep runoff away Drainage of the landfill area itself must be modified Construction of access road Weighing facilities Excavation and preparation of bottom For modern landfills, construction goes on in section Stockpiled excavated material Before the landfill liner, vadose zone, and groundwater monitoring equipment are installed Leachate collection and extraction facilities are placed within or on top of the liner groundwater Horizontal gas recovery trenches install at the bottom if VOC prod is significant and VOC should be burnt

8. Placement of waste Wastes is placed in in cells beginning along the compaction face, continuing outward and upward from the face. Height and width of cell vary between 8 to 12 ft and 10-30 ft, respectively. And covered with a thin layer of cover 6 to 12 inch Working face: varies After one or more lift have been placed, horizontal gas recovery trenches can be excavated and filled with gravel and perforated plastic pipes Once the landfill is complete, a cover layer is designed to minimize infiltration and to route drainage away from the active section. Finally, vertical gas extraction wells system may be installed at the end a

9. Reactions occurring during landfills Biological reaction Aerobic reaction followed by anaerobic reaction Physical reaction Lateral diffusion of gases and emission to the environment Movement of leachate within the landfill and underlying soil Settlement of organic waste Chemical reaction

10. Landfill classification Classification Wastes I Hazardous II Designated III MSW

11. Types of landfill Landfill for commingled waste Landfill fro shredded SW: better for compaction, but need addition space Landfill for individual waste constituents (also called monofills ) For combustion ash, asbestosand other similar material Other type of landfill Landfill designed to maximize gas production Landfill as integrated treatment units Landfill in wetland areas

12. Landfill methods: Excavated Cell/trench method Suitable for where adequate depth of cover material is available Water table is not near the surface Excavated cells are square, up to 1000 ft in width and length, with side slopes of 1.5:1 to 2:1. Trenches vary from 200 to 1000 ft in length, 3 to 10 ft in depth, and 15 to 50 ft in width.

13. Area Method The area method is used when the terrain is unstable for the excavation of cells or trenches in which to place the solid wastes. High ground water condition then use area-type landfills. Site preparation include the installation of a liner and leachate control system. Cover material must be hauled in by truck or earth-moving equipment from adjacent land or from borrow pit areas. In locations with limited availability of material that can be used as cover, compost produced from yard wastes and MSW has been used as intermediate cover material. Other technique that have been used include the use of movable temporary cover materials such as soil and geo membrane. Includes techniques

14. Canyon /Depression method Canyons, ravines, dry borrow pits have been used for landfills. The techniques to place and compact solid wastes in canyon/depression landfills vary with the geometry of the site, the characteristics of the available cover material, the hydrology and geology of the site, the type of leachate and gas control facilities to be used and the access to the site. Control of surface drainage is a critical factor in the development of canyon/depression sites. Filling for each lift starts at the head end of the canyon and ends at the mouth to prevent the accumulation of water behind the landfill. Canyon/depression sites are filled in multiple lifts and the method of operation is essentially the same as the area method. If the canyon floor is flat, the initial landfilling may be carried out using the excavated/trench method.

15. Landfill sitting considerations Factors need to be evaluated Haul distance Location restriction Available land area Site access Soil condition and topography Climatologic condition (weather, wind) Surface water hydrology (runoff and drainage) Geologic and hydrogeology conditions (movement of leachate and gases) Local environmental condition (traffic, residential area, industry) Ultimate use of completed landfill Access

16. Concerns with the landfilling of SW Uncontrolled release of landfill gases Impact of landfill gases on atmosphere Uncontrolled release of leachate Breeding and harboring of disease vectors Health and environmental impact

17. Problem Estimate required landfill area for a community with a population of 31000. Assumption: Solid waste generation: 6.4lb/capita/day Compacted specific weight= 800 lb /yd3 Average depth of compacted solid waste = 20 ft

18. Management of Landfill Gas Landfill Waste Water Landfill Gas Landfill Leachate Principal gases CO2 and CH4 Minor and traces Landfill can be think as a biochemical reactor

19. Typical Constituents in MSW gas

20. Traces constituents Henry law

21. Problem Determine the concentration of CO2 in the upper layer of the groundwater in a contact with a landfill gas at one atm and 50C. Assume that the composition of the landfill gas is 50% CO2 and 50% CH4 and the gas is saturate with water vapour.

22. Generation of Landfill gas It happens in five phases

23. Trend

24. Duration of Phases Production of gas Depends on Distribution of organic compounds Availability of the nutrients Moisture content of wastes Moisture routing through the fill Degree of initial compaction Landfill gas retardation depends on Insufficient moisture

25. Volume of gas produced

26. Problem

27. Variation of Gas production with time

28. Variation of Gas production with moisture

29. Sources of trace gases

30. Sources of Trace Gases

31. Movement of landfill gas

32. Movement of principal landfill gases Both CH4 and CO2 conc upto 40% in the lateral distance if unlined This % varies with cover material and soil type

33. Upward migration of landfill gas

34. Downward migration of landfill gas CO2 increases Hardness

35. Movement of traces

36. Problem Estimate the emission of toluene. 1 1 1 trichloroethane and vinyl chloride from the surface of a landfill due to diffusion. Data: Temp: 30 C Landfill cover material: clay loam mixture Porosity of the landfill cover material: 0.20 Landfill cover thickness: 2 ft W: 0.001

37. Control of Landfill gas

38. Gas control system Active: With Perimeter facilities Perimeter gas extraction and odor control well Perimeter gas extraction trenches Active control of landfill gas with vertical and horizontal gas extraction wells Vertical gas extraction well Horizontal gas extraction well Passive control system: Pressure reliefs vents/flares in landfill cover Perimeter interceptor trenches Perimeter barrier tranches Impermeable barriers within landfill Use of sorptive barriers within landfills for trace gases

39. Pressure reliefs vents/flares in landfill cover

40. Perimeter interceptor trenches

41. Perimeter barrier trench or slurry wall

42. Impermeable barriers with in landfills

43. Sealant for Impermeable barriers with in landfills

44. Active control with perimeter facilities Perimeter gas extraction and odor control wells Electric driven blower Radii of influence Overpulling Gas sampling port and flow control vlaves Well spacing vary between 25 -50’

45. Detail of extraction well

46. Perimeter gas extraction trenches

47. Vertical extraction Well

48. Management of landfill gas By flaring Electricity generation CO2 separation from CH4

49. Management of landfill gases Flaring of landfill gases

50. Landfill gas energy recovery unit For smaller installation < 5MW

51. For smaller installation > 5MW