To reduce the environmental impact we should ISOLATE or CONTAIN the waste in an IMPERMEABLE BARRIER

Transcription

1 To reduce the environmental impact we should ISOLATE or CONTAIN the waste in an IMPERMEABLE BARRIER 1

2 COMPONENTS OF ENGINEERED LANDFILL a) A Liner System b) A Leachate Collection Facility c) A Gas Control Facility d) A Final Cover System e) A Surface Water Drainage System f) An Environmental Monitoring System g) A Closure and Post Closure Plan 2

3 PLANNING OF LANDFILLS 3

4 LANDFILLS (SECURED LANDFILLS OR ENGINEERED LANDFILLS) Landfills are solid waste disposal (or storage) facilities designed with adequate protective measures against a) Ground water pollution b) Surface water pollution c) Air pollution d) Fire hazard e) Birds menace f) Pests/rodents g) Green house gas emissions h) Dust, wind blown litter i) Bad odour j) Slope instability and erosion 4

5 OPTIONS FOR WASTE LANDFILLING Disposal on the ground surface Disposal deep below the ground surface 5

6 Advantages of Above Ground Landfills: Drainage of leachate by gravity Large thickness of unsaturated zone below landfill Poor surface drainage can be avoided Easy inspection and maintenance. Disadvantages of Above Ground Landfills: Land-use pattern altered More surface area exposed Slope stability and erosion control measures required 6

7 Advantages of Below Ground Landfills: More waste storage per unit area Excavated material used as cover material Parks, golf courses, parking lots can be developed on completed landfill Long-term slope stability and erosion control requirements not critical Disadvantages of Below Ground Landfills: Regular pumping for leachate collection needed Good surface water drainage required YOU CANNOT GO BELOW THE GROUND IN 2 CASES WHEN THE WATER TABLE IS VERY CLOSE TO THE GROUND SURFACE AND SECOND CASE WHEN THERE IS ROCK NEAR THE GROUND SURFACE. BECAUSE EXCAVATING IN ROCK IS EXORBITANTLY EXPENSIVE. 7

8 TYPES OF LANDFILLS a) Hazardous Waste Landfills b) Non-hazardous Waste Landfills (including MSW Landfills) c) Inert waste landfills/monofills (including construction and demolition waste landfills) d) Monofills for high volume waste (including ash ponds, mine tailing ponds) e) Special landfills (including highly toxic/radioactive waste) 8

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11 LANDFILLING PHILOSOPHY a) Only that waste should be placed in landfills which has no recoverable component (of material or energy) b) Landfills (dry tombs) are not designed like bio-rectors; all biodegradable wastes should be processed for recovery of materials or energy prior to landfilling. c) The design life of a landfill is typically 50 to 75 years; beyond this life the contaminant barriers may not perform satisfactorily. d) If the waste inside a landfill stabilizes within the design life and the emissions from landfill are within the limits, then the waste disposal is final disposal, if not then waste disposal is temporary storage. 11

12 PLANNING OF LANDFILLS a) Design life b) Waste Acceptance c) Site Selection d) Site Characterization e) Landfill Layout f) Landfill Section g) Landfill Capacity h) Phased Operation i) Strategy for Management of Emissions j) Design Aspects k) Closure and Post-Closure Plan 12

13 DESIGN LIFE Design life is the total life a landfill has to spent during its lifetime. Design Life of Landfill = Active Period + Closure and Post Closure Period Active Period = 10 to 25 years Closure and Post Closure Period = 30 years 13

14 WASTE ACCEPTANCE a) Authorized waste only b) No liquid or slurry type waste c) No recyclable waste; no compostable waste d) No waste from which energy or material recovery is feasible through thermal/biological process. e) Incompatible wastes in separate landfill units f) No non-hazardous or municipal waste in HW landfills and no hazardous waste in MSW landfills g) Extremely hazardous wastes should be stabilized before landfilling or disposed in specially designed waste disposal units. 14

15 SITE SELECTION Objective: To select a site with greatest protection to its environment. At low cost With public acceptance (main issue) Factors to be considered Receptor related attributes (how many people are adjacent to that site) Pathway related attributes (position of ground water table) Source (Waste) related attributes (where are the drinking wells, where is the river source) Waste management related attributes (are you having a large waste dump or a small waste dump) 15

16 SITE SELECTION Selection Process: Potential sites are identified Site selection criteria is drawn up Data is obtained Weighted site ranking methodology is adopted 16

17 LOCATION CRITERIA (for lined landfills) Lake/Pond River Floor Plain Highway Habitation Public Park Critical Habitat Wetland Coastal Regulation Zone Airport Water Supply Well Ground Water Table Level > 200 m (> 500 DW) > 100 m Protective Embankment > 500 m > 500 m > 500 m NO NO NO > 3000 m to 20 km > 500 m 2 m below base of landfill 17

18 SITE CHARACTERIZATION Objectives: To establish that the site is suited for the intended purpose To establish baseline conditions To enable assessment of impact on the environment To undertake engineering design of the landfill To draw up a pollution monitoring programme 18

19 SITE CHARACTERIZATION Information Obtained: Surface landform, surface water drainage, surface water quality Nature and properties of subsurface strata, depth to bedrock Depth to water table, fluctuations in water table, groundwater flow and quality Current land use pattern with any history of mining or quarrying Availability of top soil, clay and other materials to be used for lining and covering/restoration of landfill Background levels of gas, noise, dust, etc. Meteorological conditions: rainfall, wind, evapotranspiration Seismicity 19

20 LANDFILL LAYOUT a) The layout of a landfill in plan is governed by the shape of the area made available for landfilling b) About 80% of the total area is used for placing the waste c) The balance 20% of the area is covered by the following: I. Built-up area office, laboratory, workshop, equipment shelters, weighing scale II. Treatment facilities, for leachate and gas and pond for storm water detention III. Fencing, green belt, roads, storm water drains IV. Temporary holding areas for waste material, construction materials. V. Environmental monitoring facilities. 20

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24 LANDFILL SECTION Factors: Topography of the area Depth to groundwater table Depth to rock Availability of liner and cover material Types: Below ground landfills Above ground landfills Slope landfills Valley landfills A combination of the above 24

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29 COMPONENTS Liner System Leachate Collection Facility Daily Cells Daily Cover Lift Phase (Yearly) Intermediate Cover Bench Final Cover System Gas Collection Facility 29

30 LANDFILL CAPACITY Factors: Quantity of waste and its compacted density Volume of waste Volume occupied by liner and cover (daily, intermediate, final) Volume reduction due to settlement Density of Waste: Biodegradable waste/municipal waste may have density of 0.6 to 1.2 t/cum Inorganic waste may have density of 1.2 to 1.6 t/cum Settlement: Inorganic compacted waste: ~5% in few years Municipal biodegradable waste: ~20% in 30 years 30

31 ESTIMATION OF LANDFILL CAPACITY (Volume/Height/Area) 1. Waste generation rate = W tons per year 2. Active life of landfill = n years 3. Total waste in n years (T) = W x n tons 4. Volume of waste (V) = T/density cu.m 5. Volume for daily cover = 0.1 V 6. Volume for liner and final cover= 0.2 V to 0.3 V 31

32 ESTIMATION OF LANDFILL CAPACITY (Volume/Height/Area) 7. Total volume (Landfill capacity) = V + 0.1V V 8. Total area available = A sq.m 9. Area for infrastructure = 0.15 A to 0.25 A = 0.2 A 10. Area for landfilling = A 0.2 A = 0.8 A 11. Height (+ depth) of landfill = 1.35 V / 0.8 A This is a preliminary estimate on the assumption that plan dimensions are much larger than the height 32

33 LANDFILL DIMENSIONS Area: desirable for full life Shape in plan: As available Depth below ground surface: restricted by depth to WT and bedrock; usually upto 7-8 m for unsupported excavation Height: Typically 15 m for aesthetic reasons; can be as high as 40 m or more (eg. in valleys) 33

34 PHASED OPERATION a) The term phase describes a sub-area of the landfill. It comprises of cells in which waste is placed daily and covered with soil at the end of the day. The daily soil cover is usually 15 cm thick. b) Each phase is designed for a period of 12 months. It is filled from the base level, above the liner, to the final cover level and then capped with the final cover, leaving a temporary sloping face with intermediate soil cover. c) It is to be ensured that each phase reaches the cover level and that the final cover is in position before the onset of monsoons. 34

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37 PHASED OPERATION d) During the monsoons the following methodology may be adopted: i. Landfill may be kept capped and non-operational; all waste may be stockpiled in a temporary holding area (covered with roof) ii. Special monsoon phases may be designed in a separate area of the landfill to place the waste. Such phases would have temporary mobile covers and a leachate collection system with high capacity 37

38 MANAGEMENT OF EMISSIONS Leachate: a) Discharge to drain b) Solar evaporation pond/forced evaporation in incinerators or evaporation plants c) Offsite treatment in ETP (Emission Treatment Plant) d) Onsite treatment in ETP 38

39 MANAGEMENT OF EMISSIONS Gas: a) Allow slow advection/diffusion/dispersion b) Passive vents c) Collect and flare d) Utilize for cooking/heating e) Utilize for power generation 39

40 GEOTECHNICAL DESIGN OF COMPONENTS a) Embankment Design b) Liner Design c) Leachate Wells and Drains d) Cover Design e) Gas Wells and Drains f) Stability Analysis g) Environmental Monitoring h) Estimation of Quantities and Costs 40

41 CLOSURE AND POST-CLOSURE PLAN Objectives: Ensure that all landfill components continue to remain functional for a long period (typically 30 years) after closure Achieve the intended end-use of landfill surface (e.g. golf course, parking area, restore to original condition) Effectively remove surface water Periodically inspect and prepare maintenance schedule 41