trp chapter 6.6 1 chapter 6.6 land disposal. trp chapter 6.6 2 structure of chapter introduction...
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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
TRP Chapter 6.6 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
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
TRP Chapter 6.6 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
TRP Chapter 6.6 6
Uncontrolled landfill: landslip
Payatas dumpsite, Philippines 2000 Source: http://www.dr-koelsch.de/html/payatas__gb_.html
TRP Chapter 6.6 7
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 8
Part A: Key principles of a landfill site
TRP Chapter 6.6 9
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
TRP Chapter 6.6 11
Choosing a site
In a depression
- preferred
On level ground
On a slope
TRP Chapter 6.6 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
TRP Chapter 6.6 13
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
TRP Chapter 6.6 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:CostLocal geology and hydrogeologyAvailability of appropriate materialsDesired degree of protection against leachate escapeLiner durability
TRP Chapter 6.6 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
TRP Chapter 6.6 16
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
TRP Chapter 6.6 17
Drainage pipes in a composite liner system
Source: Landfill of hazardous wastes, Technical report No 17, UNEP
Site design - leachate control
TRP Chapter 6.6 18
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
TRP Chapter 6.6 19
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
TRP Chapter 6.6 21
Cellular structure
Source: ISWA, Solid waste management for economically developing countries, 1996
TRP Chapter 6.6 22
Waste compaction
•Maximises void space
•Reduces risk of fires in waste
•Deters vermin
TRP Chapter 6.6 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
TRP Chapter 6.6 24
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
TRP Chapter 6.6 25
Completed landfill - cross section
TRP Chapter 6.6 26
Part B:Handling industrial wastes in
municipal landfills as an interim solution - Co-disposal
TRP Chapter 6.6 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
TRP Chapter 6.6 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 safelyRecords 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 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
TRP Chapter 6.6 30
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
TRP Chapter 6.6 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
TRP Chapter 6.6 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
TRP Chapter 6.6 33
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
TRP Chapter 6.6 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
TRP Chapter 6.6 35
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
TRP Chapter 6.6 36
Co-disposal site infrastructure 2
Source: World Bank Technical Paper No 93
Area for future co-disposal in trenches
TRP Chapter 6.6 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
TRP Chapter 6.6 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
TRP Chapter 6.6 39
Part C:Purpose-designed industrial waste
landfill sites
TRP Chapter 6.6 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
TRP Chapter 6.6 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
TRP Chapter 6.6 42
Multi-disposal site design
Source: Hazardous wastes, sources, pathways, receptors, Richard J. Watts, 1997
TRP Chapter 6.6 43
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
TRP Chapter 6.6 44
Source ???
Section through multi-disposal site
TRP Chapter 6.6 45
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
TRP Chapter 6.6 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
TRP Chapter 6.6 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
TRP Chapter 6.6 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
Pictures show AVR site in The Netherlands
TRP Chapter 6.6 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