1. Chapter 6.6 Land disposal
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2. Part A: Key principles of a landfill site
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
Slide 2 Structure of chapter
This chapter has been divided into three parts.
After an introduction to the topic of land disposal, Part A deals with the key principles of a landfill including upgrading from uncontrolled dumping of waste of all kinds, which is the urgent need in many developing economies. Much of the information in this section applies equally to municipal and hazardous waste sites but since current practice is often the uncontrolled mixing of hazardous wastes in municipal waste dumps, upgrading hazardous waste landfill also requires upgrading of municipal sites.
Part B deals with the co-disposal of hazardous wastes in municipal landfills.
Part C looks at purpose-designed landfill sites including multi-disposal of hazardous wastes and secure landfill of stabilised hazardous wastes.
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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
Slide 3 Introduction: Current status of land disposal
Landfilling/land disposal of waste is the most common disposal route for all wastes, including those with hazardous properties. However, as the slide shows, in many developing economies the standards of land disposal are very poor: many landfills are unlined, and have little or no control of leachate or surface water run-off.
Despite being at the bottom of the waste management hierarchy, land disposal has a vital role to play in the sound management of hazardous wastes. It will always be needed, in every country, since waste minimisation and recycling can never entirely eliminate waste and treatment processes themselves generally create residues which need disposal.
The short term priority in developing economies is to upgrade existing practices in order to eliminate uncontrolled dumping and bring land disposal into the hierarchy of acceptable options.
Landfill must not be treated as a cheap disposal option. The siting, design, construction, operation and closure of land disposal sites require skilled professionals. If not properly sited, built and operated, such a site can pose considerable environmental and health risks, the impact of which may not only contaminate the disposal site and surrounding area, but can even affect a distant community through groundwater or other pathways.
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4. 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
Slide 4 Risks of uncontrolled landfill
Upgrading dumps to controlled landfill requires an understanding of the issues and the possible impacts of improper land disposal of waste, in order to address them.
The slide shows some of the risks which are associated with poorly managed landfill and land disposal of wastes of all kinds, not simply hazardous wastes. If the site is uncontrolled, hazardous wastes of all kinds including industrial and hospital wastes may be disposed of there, posing an additional hazard to workers, scavengers and those that live nearby.
Landslips are a serious problem for uncontrolled waste dumps (see Slide 6).
Fires burning within the uncompacted waste can result in the waste becoming unstable, as well as creating smoke and dust which are harmful to the health of workers and people living nearby. Fires have been known to burn within sites for many months.
Once management begins, and compaction of waste takes place, the anaerobic conditions can result in gas migration.
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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
Slide 5 Risk mitigation
Regulators and waste management professionals must implement measures to limit or prevent the kind of impacts shown on the previous slide.
Mitigation of such risks may include the prohibition of certain wastes from sites (including dump sites). This will be dependent on the presence of an on-site operator with skilled staff.
Other measures might include the proper design and engineering of the site. This will include the use of liners, as well as gas and leachate collection and treatment systems. Good working practices such as waste compaction to stabilise the site, and daily cover to deter vermin and flies, are also important in mitigating risks.
All of these are covered in Part A which covers the principles of MSW landfills, partly because the same principles are common to all landfills and partly because in developing economies it is inevitable that some industrial wastes will be sent to such sites at least in the short term.
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6. Uncontrolled landfill: landslip
Slide 6 Uncontrolled landfill: landslip
As slide 4 showed, there are a number of risks associated with uncontrolled waste dumps, including the risk of landslips.
This slide shows a municipal waste site in the Philippines. Payatas dumpsite is located in Quezon City in the North-East of Manila, capital of the Philippines. Around the landfill is the township of Payatas, with around 80,000inhabitants.
In the early morning of 10 July 2000 a landslip on the dump was responsible for the deaths of more than 200 people (Source: Dr Koelsch, Geo- und Umwelttechnik), including waste pickers and their families who had occupied the huts shown in the picture.
Scavengers and waste pickers are particularly vulnerable to all of the risks associated with uncontrolled landfills, as are waste workers and people living in the neighbourhood of the site.
Payatas dumpsite, Philippines 2000
Source:
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7. Need to raise standards
Slide 7 Need to raise standards
The main reasons for the continued use of open dumps in some countries are the low priority given to waste management, and the shortage of funding.
For all wastes, open dumps pose a risk to health and the environment, but this is particularly so if hazardous wastes are also accepted at such sites.
Open dumps need either to be brought up to an acceptable standard, or closed.
Chemical fire on European dump site example of the risks of mixing hazardous wastes with MSW
Source: David C Wilson
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8. Part A: Key principles of a landfill site
Slide 8 Key principles of a landfill site
Part A looks at the key landfill principles, and this revisits the requirements for municipal solid waste sites. There are a number of valuable publications dealing with this topic (see Sources of further information), but it is useful to repeat the principles here as they are common to all landfills. What’s more, it is inevitable, at least in the short term, that some industrial wastes will be handled in MSW landfills.
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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
Slide 9 Stages in upgrading sites
It may be possible to upgrade a site which is currently an open dump so that it reaches the standard of sanitary landfill (which is still not necessarily suitable for hazardous waste disposal) or industrial waste landfill. The aim is to separate the two, but this will take time.
The slide shows the main steps which must be taken to improve an existing facility, and the level of control at each stage.
It is not possible to upgrade an open dump overnight, and a staged approach should be followed. This not only allows site surveys to be undertaken and assessments to be made of pollution, but it also allows site users to become accustomed to the new regime.
Upgrading will only be possible if the dump is in an area where there is no risk of groundwater pollution. It is only likely to be worthwhile where there is enough space remaining in the site to justify the costs. Alternatively it may be preferable to identify a new site.
(See Sources of Information for additional material on upgrading landfill sites)
It is important to note that there are also stages necessary in closing a dump site. It is not enough to simply abandon the site. Measures must be taken to ensure that wastes do not continue to be deposited at the site. Some simple remediation measures should be taken eg limiting the infiltration of water by capping the site and putting a drainage system in place around the perimiter. Where the wastes are unstable, measures should be undertaken to stabilise the site.
Open dump
No controls
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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
Slide 10 Components of a well-managed landfill operation
The slide shows essential components of a properly constructed and managed landfill site. All of these are addressed in the following slides.
It is important to note that well-chosen sites and good engineering are not enough on their own. Even the best-designed site will pose environmental hazards unless sufficient priority and resources are devoted to proper management and operation of the site, including supporting services such as training of personnel.
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11. Choosing a site In a depression - preferred On level ground On a slope
Slide 11 Choosing a site
There are three main choices for the physical design land disposal sites, depending on the availability of sites, the geology and geography of the possible site and on which offers the most stable alternative.
Depression Where possible, a depression (eg a gully or abandoned quarry) is used because it offers the most stability.
Above ground Above ground land disposal sites may be built where there is a risk to the water table or where no suitable depression exists. However there is a greater risk of the landfilled material slipping.
Slope The third option is a slope. Before using a slope to construct a landfill site, careful assessment must be made of the likely stability of the land itself and the waste. Seepage of water is a major contributor to landslides in landfills, and placing a landfill close to or on a slope may alter the natural pattern of surface waters, exposing the site to greater risk. Rainfall levels and the capacity of the drainage system must always be taken into account when siting a landfill, but more so when the site is a sloping one.
In addition to these three alternatives, some land disposal uses underground storage in caves, salt mines or deep wells. Here the character and type of the rock formation is important in deciding suitability, as well as national and local regulations.
On a slope
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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
Slide 12 Improving municipal landfill practice: site considerations
Whether upgrading dump sites or identifying new sites, there are a number of factors to be taken into account. These include the geological and hydrological characteristics of the area.
These factors will influence the design of the site and the level of environmental protection which must be put in place eg the liner, the system of leachate collection and the monitoring equipment. (See also Chapter 6.8 Site selection.)
Identification should be made of any drinking water sources in the vicinity of the proposed site, and, if it is a new operaiton, the facility should be placed as far as possible away from them. Areas liable to flooding or erosion should also be avoided when choosing new sites. The most favourable site is one containing a thick layer of clay or one which is above unusable groundwater such as a saline aquifer.
Other influences on the selection of new sites and the operaiton of existing ones include the proximity to urban areas. There will be impacts on the local community from the construction, operation and closure of the site. These impacts will include transport, noise and dust as well as the visual impacts. For new sites, measures to minimise these adverse impacts should be set out at planning stage. (See also Chapter 1.3 Developing a hazardous waste policy and strategy, Chapter 2.3 Environmental impacts and health risks and Chapter 2.4 Public awareness and communication.)
A comprehensive safety and emergency plan must form part of the operational procedures, to ensure effective response to protect the community in case of accidents or leaks.
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13. Siting a landfill: example
Solid waste management for economically developing countries, ISWA, 1996
Slide 13 Siting a landfill: example
The slide shows an example of a landfill site suitable for level ground.
Suitable for site with:
level land surface
low groundwater table
soil layer thicker than 2 metres
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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
Slide 14 Site design – liner systems
Having selected a suitable site, construction must be tailored to the specific characteristics of the site and the wastes which will be disposed of within it.
The bottom liner is one of the important design features in order to contain leachate. It is designed to remain impermeable during long term storage of waste. Multiple liner systems are frequently chosen so that if the upper liner leaks, escaping materials can be detected and caught at a lower level.
The liner system – whether it is single, double or triple layer – is key to ensuring the isolation of the waste. Permeability is influenced by the soil or rock in the base of the site, and the chosen liner. The aim is to control the escape of contaminants from the site into the surrounding environment.
The liner material should be resistant to damage eg puncture from sharp objects and should maintain its permeability even where there is a chemical leak within the site. It should be durable to last the construction, operation and closure phases which may be a period of many years. The use of double liners enables the installation of a leak detection system between the layers, to monitor for liner failure. However, cost is also a determining factor.
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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
Slide 15 Site design - liner materials
Liners may be made of natural or synthetic materials. Of the former, low permeability soils (eg clay) have been used for many years and have a number of advantages including wide availability, strength, durability, leak resistance and an ability to self-seal. The disadvantages of low permeability soils include their variability.
Bituminous materials are also used for lining landfills, because of their low permeability, damage resistance and flexibility. However, installing bituminous materials is not easy, particularly on sloping sites, and they are not homogeneous.
Bentonite is used alone or mixed with sand, and the latter offers low permeability.
In part, the choice of liner materials depends on availability and cost as well as on achieving the desired level of protection which will differ according to the type of waste to be disposed of in the site. In general, the more complex the liner system, the longer it will take to install and the higher the investment cost.
For sites which may receive hazardous wastes, either in combination with municipal solid waste or alone, studies suggest that both clay and synthetic liners might significantly change their permeability when exposed to some chemicals.
In order to reduce the risk of leachate escaping, the compatibility of the waste liner with the waste is an important factor.
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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
Slide 16 Cross-section of multiple liner system
The slide shows the different layers in an advanced liner system.
Discussion: The function and value of the different parts of the liner could be discussed.
Primary and secondary leachate collection piping
Compacted clay
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17. Site design - leachate control
Drainage pipes in a composite liner system
Slide 17 Site design - leachate control
One objective of landfill site design is to minimise leachate eg by limiting water passing into the waste. Where landfills are unlined, leachate seeps into the surrounding land. Lining the site enables the leachate to be collected. However effective the measures to reduce leachate, some is likely to be produced (depending on the waste itself and the site conditions) and its management requires its collection, treatment and disposal.
The slide shows a collection system installed in a site.
A leachate collection system is installed above and between the liners. It consists of a riser pipe extending from the sump to the ground surface to enhance leachate removal. The riser pipe allows leachate to be pumped to the surface for further treatment. Proper design of the leachate collection system is necessary to ensure it is capable of handling the volumetric flow of leachate expected. This system must remain operational within the life of the site including a post-closure period of perhaps 30 years. Therefore the materials used for its construction must be highly resistant to hazardous waste constituents.
Treating the leachate requires an understanding of its chemical composition, and this will require laboratory testing. Treatment processes may be biological, chemical or physical. (See Chapter 6.2 Physico-chemical treatment and Chapter 6.3 Biological treatment)
Source: Landfill of hazardous wastes, Technical report No 17, UNEP
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18. 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 Explosion
Carbon dioxide Asphyxiation
Nitrogen
Oxygen Fire
Hydrogen
Other trace gases Toxicity
Slide 18 Site design - landfill gas management
Landfill gas management is necessary at engineered sites.
Landfill gas is potentially explosive and contains a mixture of methane (~60%) and carbon dioxide (~40%) plus a number of trace gases. It is produced by the decomposition of organic material in the waste.
Significant changes in gas quantity and composition may result from biological and biochemical decomposition of the waste over a period of years. The seepage of landfill gas into the atmosphere contributes to global warming and at the least, measures to manage the gas should vent it for flaring.
Recovery of the gas for electricity production or for direct use in engines is widely practised. For example, in Santiago, Chile the gas is used as fuel in a chemical plant while in Rio de Janiero, Brazil it is cleaned and used as vehicle fuel.
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19. Site preparation Fencing to control access TRP Chapter 6.6 19
Slide 19 Site preparation
In addition to the preparation of the landfill void space and the gas collection and leachate control systems, there are a number of additional stages in the preparation of a site. These include:
construction of access roads, or where appropriate the upgrading or improvement of existing roads or tracks to enable vehicular access during the site construction and waste deliveries to be made
installation of utilities – power for lighting, and to operate equipment; water supplies for use by personnel in washing, preparing meals, cleaning vehicles
fencing to prevent unauthorised access to the site, and to control litter. Low litter fences should be erected close to the landfilling operations and moved as the tipping face moves.
Once the site is in operation, signage should be provided to manage the vehicle movements and make clear where users should deposit waste loads.
Fencing to control access
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20. Site operation Key factors: Waste placement in cells Waste compaction
Daily and intermediate cover
Final cover
Slide 20 Site operation
The previous slides have discussed the importance of proper site design.
However well-designed, the site will not be an improvement on an open dump unless it is properly managed and operated.
The key operational aspects for sanitary landfill are shown on this slide and the next five slides. These apply to all landfill sites, and are not specific to sites receiving hazardous wastes.
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21. Cellular structure
Slide 21 Cellular structure
The slide shows the cellular structure of a sanitary landfill.
The design and operation of a site based on a series of discrete cells has several advantages. It allows a limited ‘working face’ which improves management control. It also reduces the infiltration of rainwater and thus leachate generation.
Such a cellular structure is also used on hazardous waste sites, enabling different wastes to be kept separate.
Source: ISWA, Solid waste management for economically developing countries, 1996
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22. Waste compaction Maximises void space Reduces risk of fires in waste
Deters vermin
Slide 22 Waste compaction
Waste compaction takes place because it maximises the void space, and helps to reduce the risk of fires within the waste. Together with the daily cover regime, waste compaction also deters vermin.
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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
Slide 23 Purpose of cover
The slide shows the various reasons for undertaking daily and intermediate cover of landfill sites.
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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
Slide 24 Final cover
Final cover is used to act as a durable barrier, to stabilise the site, to improve its appearance and to enable post-closure use of the site.
The material used for final cover must be flexible, resistant to natural weathering, sunlight and ozone. It must be inspected regularly and any necessary maintenance undertaken.
The slide shows a multi-disposal site which accepts various hazardous wastes (see also Part B)
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25. Completed landfill - cross section
Slide 25 Completed landfill – cross section
The slide shows a cross section through a completed engineered landfill site suitable for MSW or hazardous waste.
The final cover is sloped, typically at a minimum of 5% to promote runoff. Post-closure, run-off must continue to be diverted and monitoring systems operated, as well as inspections to ensure that soil and wind erosion do not damage the cover integrity.
Public access must continue to be restricted.
Long term monitoring of groundwater, air quality, leachate, settlement and surrounding vegetation must be made.
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26. Part B: Handling industrial wastes in municipal landfills as an interim solution - Co-disposal
Slide 26 Part B Handling industrial wastes in municipal landfills as an interim solution - Co-disposal
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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
Slide 27 Basic requirements for co-disposal
The starting point in many developing economies is that much industrial waste is currently going to the municipal landfill.
Rather than banning it before an alternative, better-controlled solution is available, it is better to control and improve the practice as an interim solution.
The objective is to reduce the environmental and public health risks associated with the industrial wastes while at the same time planning for a long term solution. In order to achieve this, the three basic requirements are:
1 To control the waste that comes in, and to require the pretreatment of some wastes while excluding others eg flammable liquids. Wastes must be tested and detailed records kept.
2 To improve the physical arrangements for receiving and managing the wastes.
3 To employ skilled, trained staff.
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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
Slide 28 Testing and record keeping
While many of the slides in Part A deal with issues which apply equally to MSW sites and hazardous sites, testing of wastes on delivery and record keeping are specific operational and management requirements for sites which accept hazardous wastes.
It is vitally important for hazardous waste facilities of all kinds to know what it is they are delaing with. Therefore an early step in upgrading at an exisiting site is to gradually introduce a regime of testing and record keeping.
Sampling and testing of hazardous waste prior to acceptance is important to ensure that waste is acceptable for site conditions and to select appropriate disposal as well as confirming compatibility beetween wastes, and with wastes and liner. (See also Chapter 5.1 Waste handling and storage for information on waste compatibility)
The hazardous waste management system should include extensive record keeping. The records should enable detailed tracking of the wastes from their point of generation to their exact location in the completed site. (See also Chapter 5.2 Waste transport for information on manifest systems)
The information should cover the quantity and form of the wastes (eg solidified in drums), the date at which it was placed in the site, and details of who supplied it. Laboratory analysis reports should form part of the record of each waste deposition. Using a grid system based on the sections or cells within the site, an exact location can be recorded.
It is essential that proper management systems are in place: landfill must not be treated as a cheap option for hazardous waste disposal.
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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
Slide 29 Compatibility of hazardous wastes
Testing and sampling will ensure that wastes are compatible with one another and with the site liner. As was shown on slide 15, compatibility between wastes and the liner is an important factor in sites which accept hazardous wastes. (See also Chapter 5.1 Waste handling and storage for additional information about waste compatibility)
Compatibility of the wastes themselves is also important if unwanted reactions are to be avoided. Such reactions might include the generation of heat, or the emission of toxic or flammable gases.
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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
Slide 30 Co-disposal
Co-disposal describes the process of disposing of small amounts of hazardous wastes together with larger quantities of other wastes, such as municipal solid waste, at carefully controlled application rates in sanitary landfill.
It relies on the physical, chemical and biological degradation of the waste material, and the attentuation of the hazardous materials by the non-hazardous components.
Co-disposal should only take place under controlled conditions in an engineered and managed landfill site.
A properly designed and managed co-disposal site should not be confused with the existing widespread practice of uncontrolled disposal of hazardous wastes at municipal waste dumps.
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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
Slide 31 Co-disposal - considerations and status
Co-disposal of different types of wastes in the landfill must be undertaken with great care because of the variability and complexity of both the hazardous wastes and the municipal wastes with which it will be placed.
It is difficult to predict all the chemical reaction products that might be produced. For example, both organic and inorganic wastes may be subject to oxidation, reduction, combination and decomposition reactions involving hazardous constituents inside the landfill.
The complexity of these reactions combined with the varying degree of biological activity within the site make it difficult accurately to predict results.
In addition, other parameters such as temperature and pH are important influences on biological or chemical reactions, and these in turn influence the rate of production, and the complexity, of leachate.
Co-disposal is, in principle, suitable for treating solid, liquid and sludge wastes, and although it was never recommended in the USA due to previous bad experience with uncontrolled sites, it has been widely practised in a large number of countries. Notable among these is the UK where co-disposal has been used for the last 30 years.
While there is an increasing trend for co-disposal to be phased out in many developed countries, for example across Europe in the terms of the EC Landfill Directive, it may still have a vauable interim role in industrialising countries.
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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
Slide 32 Wastes suitable for co-disposal
The slide shows some low-risk hazardous wastes which may be suitable for co-disposal in sanitary landfills together with municipal wastes.
The unpredictability of reactions within the landfill make it vital that co-disposal must only be undertaken with appropriate wastes.
Wastes which are not suitable for co-disposal also include wastes containing PCBs and PAH, oxidising, reactive and flammable wastes, as well as bulk quantities of aqueous and liquid wastes.
Co-disposal should only ever be undertaken by skilled personnel in controlled conditions. It is important to ensure that the wastes are compatible with the liner materials as well as with one another.
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33. Co-disposal - maximum concentrations
Waste Concentration
Acid wastes m3 acid / tonne of MSW
Heavy metals waste g soluble chromium, copper, lead,
arsenic, nickel or zinc /tonne of MSW
10g cadmium / tonne of MSW
2g soluble mercury / tonne of MSW
Phenolic wastes kg of total phenols / tonne of MSW
Cyanide wastes g/ tonne of MSW
Total organic carbon kg / tonne of MSW
Oil, grease and kg waste/ tonne of MSW
hydrocarbon wastes
Slide 33 Co-disposal - recommended maximum concentrations
These figures are based on UK research in the 1980s, and should be used only as a guide for the upper limits, and not as levels which can safely be reached. The aim should be to achieve concentrations progressively lower than these. Lower limits may apply in different geological or climatic conditions, or with less stringent on-site management and control.
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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
Slide 34 Components of a well-managed co-disposal operation
The slide shows some of the most important factors for sound co-disposal of hazardous wastes with municipal waste in an engineered and managed site.
Discussion: Trainers are encouraged to discuss each of the points on the slide
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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
Slide 35 Co-disposal site infrastructure
The slide identifies the key issues for co-disposal site construction and operation.
Discussion: each of the points should be discussed in detail.
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36. Co-disposal site infrastructure 2
Area for future co-disposal in trenches
Slide 36 Co-disposal site infrastructure
The previous slide listed the key issues for co-disposal sites, which are illustrated on this slide.
Source: World Bank Technical Paper No 93
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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
Slide 37 Hazardous waste placement - practicalities
The practical aspects of operating a co-disposal site differ from those for sanitary landfill. Small quantities of hazardous wastes (which have first been assessed for suitability) can be disposed at at the working face of the land disposal operation.
Alternatively, trenches can be dug into the MSW which has already been placed. The slide shows the factors which must be taken into account in the latter case.
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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
Slide 38 Co-disposal case study - Asbestos waste
The slide shows the procedures necessary in order for asbestos wastes to be accepted in a co-disposal operation.
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39. Part C: Purpose-designed industrial waste landfill sites
Slide 39 Part C: Purpose-designed industrial waste landfill sites
The previous sections have looked at upgrading uncontrolled dumps, and using MSW landfill sites for the interim disposal of hazardous wastes.
Part C looks at three types of purpose-designed sites for hazardous wastes. Multi-disposal, secure landfill and the ‘ultimate’ landfill.
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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
Slide 40 Option 1: multi-disposal
The term ‘secure landfill’ is used to describe a facility specifically engineered for the disposal of hazardous wastes. However, the definition is used differently in different countries, depending on the national regulations. This part of the chapter looks at the disposal of a variety of hazardous wastes in a single secure site, a method which is commonly used in the USA.
The design and construction of a secure landfill site are key factors in achieving the objective of segregating and isolating the wastes. Management and pollution control measures for secure landfill are different from those used at sanitary landfills where co-disposal is practised.
The site is divided into cells, each of which has its own liner, leachate and gas collection system and gas management. The bottom liner is one of the important design features. It must remain impermeable during long term storage of waste. Multiple liner systems are frequently chosen so that if the upper liner leaks, escaping material can be detected and caught at a lower level. (See also Part A slides re landfill liner construction and leachate collection/treatment systems)
Cells also have monitoring devices to ensure that surface and groundwater are protected from contamination.
Bulk hazardous wastes are spread out in layers and compacted by heavy equipment before covering with soil at the end of each working day.
Containers or drums of solidified hazardous wastes are placed upright in the cell using a forklift or barrel snatches. Sufficient spaces need to be reserved around the area of the containers for placement and compaction of compatible bulk hazardous wastes or soils. This is covered by a compacted layer of cover soil at the end of each working day. All leachate collected from the landfill must be treated. Care must be taken with drums as they can adversely affect the stability of the site.
TRP Chapter

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
Slide 41 Wastes suitable for disposal in multi-disposal site
Some typical hazardous wastes which are disposed of in such sites include drummed and bulk solid wastes and incinerator ash.
Liquid wastes are not normally permitted without pre-treatment.
All wastes must meet the treatment standards specified by the regulations or in the conditions set by the site’s operating permit. Typically wastes must be biologically, physically and/or chemically treated to reduce toxicity and mobility prior to disposal.
There are a number of different types of treatment which might be used to achieve this eg solidification. (See Chapter 6.4 Stabilisation and solidification)
It is important to note that there are no general rules for such disposal, and each waste type’s compatibility must be considered in relation to other wastes in the site.
Multi-disposal has also been used for chlorinated solvents, pesticides and cyanide wastes but this is not recommended.
TRP Chapter

42. Multi-disposal site design
Slide 42 Multi-disposal site design
The slide shows the layout of a site used for disposing of a variety of hazardous wastes in cells.
Source: Hazardous wastes, sources, pathways, receptors, Richard J. Watts, 1997
TRP Chapter

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
Slide 43 Multi-disposal site operation
The slide shows some of the key factors for safe operation of multi-disposal sites.
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44. Source ??? Section through multi-disposal site TRP Chapter 6.6 44
Slide 44 Section through multi-disposal site
The slide shows a site used for the disposal of hazardous wastes in groups of stacked containers.
The cells are separated from each other by fill.
Source ???
TRP Chapter

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
Slide 45 Option 2: Secure landfill of stabilised wastes
As has been stated with multi-disposal, the structure of a landfill designed to accept a variety of hazardous wastes is made up of discrete containment cells, each of which is operated and managed as a separate unit. Cells may be constructed with multiple liners, leachate collection systems and ground monitoring devices to ensure that the surface and groundwater are protected from contamination.
Incompatible waste types are placed in different cells.
The design and construction of a secure landfill are key factors in achieving the objective of segregating and isolating the wastes. Management and pollution control measures for secure landfill are similar those used in sanitary landfills.
The method of hazardous waste landfill is dictated largely by the regulations. In some countries eg France, secure landfill sites accept only hazardous wastes which have first been stabilised.
This makes the management of the landfilling operation simpler, and can also enable a high level of control to be achieved by regulators.
TRP Chapter

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
Slide 46 Basic principles of secure landfill of stabilised wastes
Secure landfill of stabilised wastes requires a site which is engineered and lined, similar to that used for sanitary landifll of MSW. The layout also uses a cellular design. However with secure landfill each cell is filled with with stabilised waste.
TRP Chapter

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
Slide 47 Adaptation of secure landfill of stabilised hazardous wastes
Examples of such adaptations include Class 1 hazardous waste landfills in France eg the Villeparisis site, and the site at Aszod in Hungary.
TRP Chapter

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
Slide 48 The ‘ultimate’ landfill
While it is not widely used, this method of landfilling hazardous wastes uses a lined concrete basin which is covered by a roof. Each cell is sealed with a concrete layer when completed.
Pictures show AVR site in The Netherlands
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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