Transcript Hazardous Wastes Introduction

Chapter 6.6
Land disposal
TRP Chapter 6.6 1
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
Semi controlled landfill
Designated dump
Open dump
Engineering & operational
control measures in place
Site supervised; controls
over wastes accepted/
waste placement; periodic
waste cover
Dumping kept within
designated area; no
control over operation
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
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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
Clay
Bentonite liners
Pulverised Fuel Ash (PFA)
Synthetic lining materials
Polyethylene
- HDPE
- 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:
Gas end uses:
•surface and sub-surface
monitoring
Fuel eg in vehicles, boilers,
kilns & furnaces
•excavated pits
•boreholes and wells
Power eg gas turbines,
diesel engines
Gas components Typical values %
Methane
63.8
Carbon dioxide
33.6
Nitrogen
2.4
Oxygen
0.16
Hydrogen
0.05
Other trace gases
Risks
Explosion
Asphyxiation
Fire
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
•weather resistant
•flexible
•regularly inspected & maintained
Vegetation
Top cover
Aims:
• to stabilise site
• improve its
appearance
• enable postclosure use
Drainage layer
Clay layer
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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 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:
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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
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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 wastes
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Source: World Bank Technical paper 93
Components of a well-managed
co-disposal operation
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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 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
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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Section through multi-disposal site
Source ???
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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
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