TRP Chapter 6.6 1

Chapter 6.6 Land disposal

TRP Chapter 6.6 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

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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

TRP Chapter 6.6 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

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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

Open dump

Semi controlled landfill

Designated dump

Sanitary landfill

No controls

Dumping kept within designated area; no control over operation

Site supervised; controls over wastes accepted/ waste placement; periodic waste cover

Engineering & operational control measures in place

Industrial waste landfill

TRP Chapter 6.6 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

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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

Suitable for site with:

level land surface

low groundwater table

soil layer thicker than 2 metres

Solid waste management for economically developing countries, ISWA, 1996

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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:CostLocal geology and hydrogeologyAvailability of appropriate materialsDesired degree of protection against leachate escapeLiner 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 layerPrimary geomembrane layer

Primary and secondary leachate collection piping

Secondary geomembrane layer

Secondary leachate collection layer acts as leak detection

Compacted clay

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Drainage pipes in a composite liner system

Source: Landfill of hazardous wastes, Technical report No 17, UNEP

Site design - leachate control

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Site design - landfill gas management

Gas components Typical values % RisksMethane 63.8 ExplosionCarbon dioxide 33.6 AsphyxiationNitrogen 2.4Oxygen 0.16 Fire Hydrogen 0.05Other trace gases Toxicity

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

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Site preparation

Fencing to control access

TRP Chapter 6.6 20

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

Vegetation

Top cover

Drainage layer

Clay layer

Aims:• to stabilise site• improve its

appearance • enable post-

closure use

Final cover must be: •durable •flexible

•weather resistant•regularly inspected & maintained

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Completed landfill - cross section

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Part B:Handling 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 safelyRecords 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-disposalCo-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 > 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 wastesSource: 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 typesRoadways should be clearly signpostedTrenches should be clearly marked and fencedWheel cleaners should be provided for vehicle entrance and exitLaboratory facilities should be available on site for simple analysisHolding area is needed for lorries to be checkedStorage area

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Co-disposal site infrastructure 2

Source: World Bank Technical Paper No 93

Area for future co-disposal in trenches

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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 C:Purpose-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

containersSeparate cells from each other by fillRecord different HW types and their originDevise emergency plan for spills and accidentsRequire the use of heavy machineryProvide training for all personnelEnsure 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 regulationsAccepts only cement-stabilised wastes,

possibly certain other solid wastes

Simplifies managementEnables 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