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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

Chapter 6.6 Land disposal

TRP Chapter 6.6 1

structure of chapter
Structure of chapter


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

introduction current status of landfill
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

risks of uncontrolled landfill
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

risk mitigation
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

uncontrolled landfill landslip
Uncontrolled landfill: landslip

Payatas dumpsite, Philippines 2000


TRP Chapter 6.6 6

need to raise standards
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

stages in improving landfills
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

components of a well managed landfill operation
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

choosing a site
Choosing a site

In a depression

- preferred

On level ground

On a slope

TRP Chapter 6.6 11

improving municipal landfill practice site considerations
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

siting a landfill example
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

site design liner systems
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

site design liner materials
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

cross section of multiple liner system
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


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

site design landfill gas management
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

site preparation
Site preparation

Fencing to control access

TRP Chapter 6.6 19

site operation
Site operation
  • Key factors:
  • Waste placement in cells
  • Waste compaction
  • Daily and intermediate cover
  • Final cover

TRP Chapter 6.6 20

cellular structure
Cellular structure

Source: ISWA, Solid waste management for economically developing countries, 1996

TRP Chapter 6.6 21

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

TRP Chapter 6.6 22

purpose of cover
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

final cover
Final cover
  • Final cover must be:
  • durable
  • flexible
  • weather resistant
  • regularly inspected & maintained


Top cover

  • Aims:
  • to stabilise site
  • improve its appearance
  • enable post-closure use

Drainage layer

Clay layer

TRP Chapter 6.6 24

part b handling industrial wastes in municipal landfills as an interim solution co disposal
Part B:Handling industrial wastes in municipal landfills as an interim solution - Co-disposal

TRP Chapter 6.6 26

basic requirements for co disposal
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

testing and record keeping
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

compatibility of hazardous wastes
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

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

co disposal considerations status
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


  • 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

wastes suitable for co disposal
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

co disposal maximum concentrations
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

components of a well managed co disposal operation
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

co disposal site infrastructure 1
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

co disposal site infrastructure 2
Co-disposal site infrastructure 2

Area for future co-disposal in trenches

Source: World Bank Technical Paper No 93

TRP Chapter 6.6 36

hazardous waste placement practicalities
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

co disposal case study asbestos waste
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

option 1 multi disposal
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

wastes suitable for disposal in multi disposal site
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

multi disposal site design
Multi-disposal site design

Source: Hazardous wastes, sources, pathways, receptors, Richard J. Watts, 1997

TRP Chapter 6.6 42

multi disposal site operation
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

option 2 secure landfill of stabilised wastes
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

basic principles of secure landfill of stabilised wastes
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

adaptation of secure landfill of stabilised hazardous wastes
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

option 3 the ultimate landfill
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

chapter 6 6 summary
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