Chapter 6.6 Land disposal

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Chapter 6.6 Land disposal
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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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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

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Risks of uncontrolled landfill

• Leachate leakage into groundwater or rivers
• Contaminated surface water run-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

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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

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Uncontrolled landfill landslip
Payatas dumpsite, Philippines 2000 Source
http//www.dr-koelsch.de/html/payatas__gb_.html
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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
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Part A Key principles of a landfill site
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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
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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

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Choosing a site
In a depression - preferred
On level ground
On a slope
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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

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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

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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

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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

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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
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Site design - leachate control
Drainage pipes in a composite liner system
Source Landfill of hazardous wastes, Technical
report No 17, UNEP
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Site design - landfill gas management

• Gas monitoring by
• surface and sub-surface monitoring
• excavated pits
• boreholes and wells

Gas end uses Fuel eg in vehicles, boilers,
kilns furnaces Power eg gas turbines, diesel
engines
Gas components Typical 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
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Site preparation
Fencing to control access
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Site operation

• Key factors
• Waste placement in cells
• Waste compaction
• Daily and intermediate cover
• Final cover

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Cellular structure
Source ISWA, Solid waste management for
economically developing countries, 1996
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Waste compaction

• Maximises void space
• Reduces risk of fires in waste
• Deters vermin

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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

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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
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Completed landfill - cross section
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Part BHandling industrial wastes in municipal
landfills as an interim solution - Co-disposal
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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

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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

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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
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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

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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

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Wastes suitable for co-disposal

• Bottom ash from waste incineration
• Contaminated soils
• Heavy metal hydroxides (pH gt 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

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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
Source World Bank Technical paper 93
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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

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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

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Co-disposal site infrastructure 2
Area for future co-disposal in trenches
Source World Bank Technical Paper No 93
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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

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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

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Part CPurpose-designed industrial waste
landfill sites
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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

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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

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Multi-disposal site design
Source Hazardous wastes, sources, pathways,
receptors, Richard J. Watts, 1997
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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

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Source ???
Section through multi-disposal site
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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

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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

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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

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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
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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