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Chapter 6.6 Land disposal

Chapter 6.6 Land disposal. Structure of chapter. Introduction Part A: Key principles of a landfill site Part B: Handling industrial wastes in municipal landfills as an interim solution - Co-disposal Part C: Purpose-designed industrial waste landfill sites .

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Chapter 6.6 Land disposal

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  1. Chapter 6.6 Land disposal TRP Chapter 6.6 1

  2. Structure of chapter Introduction Part A: Key principles of a landfill site Part B: Handling industrial wastes in municipal landfills as an interim solution - Co-disposal Part C: Purpose-designed industrial waste landfill sites TRP Chapter 6.6 2

  3. Introduction: Current status of landfill • Many industrialising countries are still practising open dumping • Uncontrolled disposal of hazardous waste on municipal and sanitary landfills • Many sites are unlined, with little management of landfill gas or treatment of leachate • Poor operational standards of sites poses threats to public health and environment • Short term priorities: • to raise standards • eliminate uncontrolled dumping • Long term: • some land disposal will still be needed TRP Chapter 6.6 3

  4. Risks of uncontrolled landfill • Leachate leakage into groundwater or rivers • Contaminated surface waterrun-off into soil, watercourses • Uncontrolled burning • Gas migration into soil and air • Landslip of unstable wastes • Flies and vermin • Dust and odours • Poor disposal practices can cause: • harm to human health - workers, site neighbours and scavengers • damage to flora • explosions and fires TRP Chapter 6.6 4

  5. Risk mitigation • Measures to mitigate risks include: • prohibition of certain wastes • proper site selection • waste compaction and daily cover • landfill liners • gas & leachate collection/treatment • design & engineering to control waste deposition, water ingress TRP Chapter 6.6 5

  6. Uncontrolled landfill: landslip Payatas dumpsite, Philippines 2000 Source: http://www.dr-koelsch.de/html/payatas__gb_.html TRP Chapter 6.6 6

  7. Need to raise standards Chemical fire on European dump site 1993 - example of the risks of mixing hazardous wastes with MSW Source: David C Wilson TRP Chapter 6.6 7

  8. Part A: Key principles of a landfill site TRP Chapter 6.6 8

  9. Stages in improving landfills Sanitary landfill Industrial waste landfill Engineering & operational control measures in place Site supervised; controls over wastes accepted/ waste placement; periodic waste cover Semi controlled landfill Dumping kept within designated area; no control over operation Designated dump Open dump No controls TRP Chapter 6.6 9

  10. Components of a well-managed landfill operation • Well chosen, properly designed site • Bottom liner - to protect soil and groundwater • Leachate collection and treatment - to prevent contamination of groundwater • Gas management - to prevent damage to soil and escape to air • Waste placement in cells - for operational control and to reduce rainfall infiltration • Waste compaction - to limit access by vermin and to reduce risk of fires • Daily and intermediate cover • Final cover TRP Chapter 6.6 10

  11. Choosing a site In a depression - preferred On level ground On a slope TRP Chapter 6.6 11

  12. Improving municipal landfill practice: site considerations Need to take into account: • geological & hydrological characteristics • eg drinking water sources in vicinity, areas liable to flooding or erosion • proximity to urban areas • Preferred sites may include: • sites containing thick clay layer • sites above unusable groundwater TRP Chapter 6.6 12

  13. Siting a landfill: example Solid waste management for economically developing countries, ISWA, 1996 Suitable for site with: • level land surface • low groundwater table • soil layer thicker than 2 metres TRP Chapter 6.6 13

  14. Site design - liner systems • Single liner • Clay or synthetic liner • Composite or double lined • One clay liner and one synthetic liner • Two synthethetic liners Liner selection criteria: • Cost • Local geology and hydrogeology • Availability of appropriate materials • Desired degree of protection against leachate escape • Liner durability TRP Chapter 6.6 14

  15. Site design - liner materials Natural lining materials Synthetic lining materials Clay Polyethylene Bentonite liners - HDPE Pulverised Fuel Ash (PFA) - LDPE Polyvinyl chlorine (PVC) Chlorinated polyethylene TRP Chapter 6.6 15

  16. Cross-section of multiple liner system Geotextile filter Stone/ gravel layer Primary geomembrane layer Secondary leachate collection layer acts as leak detection Secondary geomembrane layer Primary and secondary leachate collection piping Compacted clay TRP Chapter 6.6 16

  17. Site design - leachate control Drainage pipes in a composite liner system Source: Landfill of hazardous wastes, Technical report No 17, UNEP TRP Chapter 6.6 17

  18. Site design - landfill gas management • Gas monitoring by: • surface and sub-surface monitoring • excavated pits • boreholes and wells Gas end uses: Fueleg in vehicles, boilers, kilns & furnaces Powereg gas turbines, diesel engines Gas componentsTypical values %Risks Methane 63.8 Explosion Carbon dioxide 33.6 Asphyxiation Nitrogen 2.4 Oxygen 0.16 Fire Hydrogen 0.05 Other trace gases Toxicity TRP Chapter 6.6 18

  19. Site preparation Fencing to control access TRP Chapter 6.6 19

  20. Site operation • Key factors: • Waste placement in cells • Waste compaction • Daily and intermediate cover • Final cover TRP Chapter 6.6 20

  21. Cellular structure Source: ISWA, Solid waste management for economically developing countries, 1996 TRP Chapter 6.6 21

  22. Waste compaction • Maximises void space • Reduces risk of fires in waste • Deters vermin TRP Chapter 6.6 22

  23. Purpose of cover • Improves site appearance • Minimises wind-blown litter • Reduces landfill odours • Inhibits colonisation by vermin & vectors • Reduces rainwater infiltration thus reducing leachate • Controls gas and leachate migration • Reduces soil erosion TRP Chapter 6.6 23

  24. Final cover • Final cover must be: • durable • flexible • weather resistant • regularly inspected & maintained Vegetation Top cover • Aims: • to stabilise site • improve its appearance • enable post-closure use Drainage layer Clay layer TRP Chapter 6.6 24

  25. Completed landfill - cross section TRP Chapter 6.6 25

  26. Part B:Handling industrial wastes in municipal landfills as an interim solution - Co-disposal TRP Chapter 6.6 26

  27. Basic requirements for co-disposal • Control the waste that comes in • require pretreatment of some wastes • exclude some wastes eg flammable liquids • test wastes • keep detailed records • Improve waste reception and handling systems • Employ skilled, trained staff TRP Chapter 6.6 27

  28. Testing and record keeping • Important to know what is being handled • A testing and record keeping regime should be introduced when upgrading an existing site or starting a new one • Enables detailed tracking of wastes from point of generation to location in completed site • Hazardous wastes should be tested: • prior to acceptance to ensure appropriate disposal and waste compatibility • again on delivery to verify composition • Waste details must be recorded and records stored safely • Records should provide: • details of sources - waste generator, transport contractor • composition, form and quantity of wastes • date of placement • exact location in site TRP Chapter 6.6 28

  29. Compatibility of hazardous wastes One of the reasons for upgrading is to reduce the potential for harm from the uncontrolled mixing of incompatible hazardous wastes TRP Chapter 6.6 29

  30. Co-disposal • Co-disposal is the disposal of selected hazardous wastes with other heterogeneous wastes such as biodegradable municipal solid waste, industrial & commercial wastes • it takes place in properly managed sanitary landfill • it is a highly skilled and technically controlled operation • it is suitable for selected solid and sludge wastes at controlled rates of application • it uses the physical, chemical and biological processes within an MSW landfill to ‘treat’ hazardous constituents • it is not the same as uncontrolled mixing of hazardous wastes and MSW TRP Chapter 6.6 30

  31. Co-disposal - considerations & status Co-disposal needs great care because: • both hazardous wastes and MSW are variable and complex • it is difficult to predict chemical & biological reactions Co-disposal: • has been discredited by uncontrolled past practice • has been widely practised in parts of Europe eg UK • is being phased out under EU Landfill Directive requirements • is worth considering as short-medium term option • is better than uncontrolled disposal TRP Chapter 6.6 31

  32. Wastes suitable for co-disposal • Bottom ash from waste incineration • Contaminated soils • Heavy metal hydroxides (pH > 8) • Slag, bitumen waste • Oil sludges, paint sludges, tannery sludges • AVOID aqueous wastes, bulk liquid wastes • AVOID mixing incompatible wastes • CHECK wastes compatible with liner material TRP Chapter 6.6 32

  33. Co-disposal - maximum concentrations Waste Concentration Acid wastes 0.1m3 acid / tonne of MSW Heavy metals waste 100g soluble chromium, copper, lead, arsenic, nickel or zinc /tonne of MSW 10g cadmium / tonne of MSW 2g soluble mercury / tonne of MSW Phenolic wastes 2kg of total phenols / tonne of MSW Cyanide wastes 1g/ tonne of MSW Total organic carbon 5kg / tonne of MSW Oil, grease and 2.5 kg waste/ tonne of MSW hydrocarbon wastes TRP Chapter 6.6 33 Source: World Bank Technical paper 93

  34. Components of a well-managed co-disposal operation • A continuing supply of municipal waste • Trained operational manager and staff • Sufficient mobile equipment for site preparation • No scavenging should be permitted • No direct burning of waste on site • Ensure only suitable waste types are deposited - need to test all wastes prior to acceptance • Check and record waste types and their origin at the site entrance • Supervised disposal at landfill face or in trenches or pits dug into MSW at least 6 months old • Regular inspections on site TRP Chapter 6.6 34

  35. Co-disposal site infrastructure 1 Separate areas of landfill should used for different hazardous waste types Roadways should be clearly signposted Trenches should be clearly marked and fenced Wheel cleaners should be provided for vehicle entrance and exit Laboratory facilities should be available on site for simple analysis Holding area is needed for lorries to be checked Storage area TRP Chapter 6.6 35

  36. Co-disposal site infrastructure 2 Area for future co-disposal in trenches Source: World Bank Technical Paper No 93 TRP Chapter 6.6 36

  37. Hazardous waste placement - practicalities • At landfill face: • suitable only for small quantities of solid waste • Trenches or pits dug into MSW: • MSW at least 6 months old • thick layer of MSW below pit • cover after deposit • for particuarly difficult wastes, seal pit after each deposit • all operations must be supervised TRP Chapter 6.6 37

  38. Co-disposal case study Asbestos waste • Aim: • Containment, preventing human contact with, or airborne release of, asbestos • Process: • All wastes must be delivered in double-wrapped, sealed bags or containers • No mechanical handling or compaction which may damage containment • Pits should be excavated in advance • Bags/containers should be placed into pit • Pit covered and sealed immediately • Location recorded to prevent future re-excavation TRP Chapter 6.6 38

  39. Part C:Purpose-designed industrial waste landfill sites TRP Chapter 6.6 39

  40. Option 1: multi-disposal • Requires secure landfill site dedicated to disposal of hazardous waste • Site must be: • Highly engineered • Have discrete cells for different waste types, separated by barriers • Designed to: • resist leakage • segregate incompatible wastes • contain waste in a safe manner • prohibit contact between landfill contents and surrounding environment • Method commonly used in USA TRP Chapter 6.6 40

  41. Wastes suitable for disposal in multi-disposal site • Drummed and bulky solids • Pretreated sludges • Metal-finishing wastes eg lead-, chromium-, copper- and nickel-bearing wastes • Contaminated soils • Incinerator ash TRP Chapter 6.6 41

  42. Multi-disposal site design Source: Hazardous wastes, sources, pathways, receptors, Richard J. Watts, 1997 TRP Chapter 6.6 42

  43. Multi-disposal site operation • Check waste compatibility • Control types of HW waste to be buried • Place chemical HW in groups of stacked containers • Separate cells from each other by fill • Record different HW types and their origin • Devise emergency plan for spills and accidents • Require the use of heavy machinery • Provide training for all personnel • Ensure health and safety of operators TRP Chapter 6.6 43

  44. Section through multi-disposal site Source ??? TRP Chapter 6.6 44

  45. Option 2:Secure landfill of stabilised wastes • Driven by regulations • Accepts only cement-stabilised wastes, possibly certain other solid wastes • Simplifies management • Enables higher level of regulatory control Standard practice in EU and increasingly in other countries TRP Chapter 6.6 45

  46. Basic principles of secure landfill of stabilised wastes • Similar to sanitary landfill: • engineered, lined, top cover • cellular design/layout • Each cell filled with stabilised waste • Examples of secure landfill for stabilised hazardous waste include: • Ratchaburi secure landfill, Thailand • Capacity 100,000 tonnes of HW • Shenzhen secure landfill, China • Capacity 23,000 cubic metres of HW TRP Chapter 6.6 46

  47. Adaptation of secure landfill of stabilised hazardous wastes • Relies on structural properties of stabilised waste • Cement-stabilised wastes built up either in discrete blocks or monolithic ‘celluar hills’ • Each batch left for a period to monitor structural strength before continuing to build the landfill TRP Chapter 6.6 47

  48. Option 3: The ‘ultimate’ landfill • Consists of: • lined concrete basin • movable roof • wastes placed by overhead crane • may accept a variety of solid wastes • each cell topped by concrete Pictures show AVR site in The Netherlands TRP Chapter 6.6 48

  49. Chapter 6.6 Summary • Need to control landfill, to mitigate risks - open dumping not acceptable • Stages in upgrading and design, and operational standards necessary • Co-disposal as an interim solution - requires good management, skilled staff • Purpose-designed landfill for hazardous wastes TRP Chapter 6.6 49

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