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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LandfillLeachates in Landfills
Nathan NarendranathanM.Eng.Sc., C.P.Eng
Infratech Environmental
AustraliaEmail: nn@infra-tech.au
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How do landfills perform?Landfills perform by controlling andmanaging the movements of fluids (i.e.liquids and gasses) around, into and out ofthe contaminated waste volume.
Base barrier system functions:(1) To minimise the escape of
leachate into the foundation(2) To prevent contamination of
groundwater
Cap barrier system functions:(1) To control moisture filtration
into the waste(2) To collect gas flows from the
waste(3) To prevent odours, and
sources of disease(4) To meet erosion, aesthetic and
other functional criteria
Rainfall
Cap barrier
systemGas Flow
Leachate flowContained waste
Foundation
Base barrier
system
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LAND FILL WATER BALANCEPrecipitation
Evapotranspiration
Percolation into Waste
SurfaceRunoff
Surface
Runoff
Leachate
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Precipitation
Run off
Vertical Percolation
Topsoil
Rooting Layer
BarrierLayer
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE GENERATION
ASSESSMENT OF
QUANTITY &
QUALITY
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE QUANTITY
PRECIPITATION
GROUND WATER INFLUX
WASTE MOISTURE CONTENT
FINAL COVER DESIGN
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
WHY LEACHATE QUALITYASSESSMENT
WASTE HAZARD IDENTIFICATION
CHOOSE LAND FILL DESIGN
LEACHATE TREATMENT PLANT DESIGN
FORMULATE GROUND WATER
MONITORING PARAMETERS AND REGIME
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
APPROACHES
NORMALLY WASTE CHARECTERISATIONWILL PRECEDE
LAB TESTS BULK TEST, TCLP
FIELD TESTS LYSIMETER ETC.
PREDICTIVE MODELLING
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE QUANTITY
PRECLOSURE RATE
POST CLOSURE RATE
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
SOME FACTORS
COVER OR NOT TO COVER HOW LONG BEFORE TREATMENT IS NEEDED? 10,
20, 40 YRS.?
CLIMATIC CONDITION
OPERATION OF LANDFILL
WASTE COMPOSITION
ELAPSED TIME
AMBIENT TEMPERATURE AVAILABLE MOISTURE , OXYGEN
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Leachate
Leakage CollectionPipe
LinerCollection
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
PLAN VIEW
Cleaning Port
To Tank
AA
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
NAL
Landfill
Clay Stratum
Sandy Aquifer
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Water flow Direction
GWT
Bedrock
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE COLLECTION
Leachate Collection Pipes
Clay Liner
Compacted Subbase
Drainage Blanket
SyntheticMembraneLiner
Double lined landfill with a single collection system: scheme 1
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE COLLECTION
Double lined landfill with a single collection system: scheme 2
Clay Liner
Leachate Collection Pipes
Drainage Blanket
SyntheticMembrane
Liner
Compacted Subbase
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE COLLECTION
scheme 3 Leachate Collection Pipes
Drainage Blanket
ClayLiner
BentoniteAmendedSoil liner
Compacted Subbase
Double lined landfill with a single collection system: scheme 3
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE COLLECTION
Scheme 1
Leachate Collection Pipe
Drainage Blanket
SyntheticMembrane
Liner
Compacted Subase
Multiple lined landfill with two collection systems
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE COLLECTION
Scheme 2
Leachate Collection Pipes
Drainage Blanket
Synthetic
MembraneLiner
Clay Liner
Compacted Subbase
Multiple lined landfill with two collection systems
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE COLLECTION
Drainage Blankets
CompositeLiner
ClayEquivilantLiner
Subbase Replaced with Compacted
Bentonite Amended Soil or Clay Liner
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE COLLECTION
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
STORM WATER MANAGEMENT
STORM WATER DITCHES
CULVERTS & MANHOLES
STORM WATER BASINS
SEDIMENTATION TANK
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
DRAINAGE FOR LEACHATE
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
LEACHATE PONDS
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Leachate Drainage Layer
Must have adequate capacity to handle the maximum flowproduced during landfill operations.
Can use granular materials, with hydraulic conductivity1*10^(-3) m/sec, or a geocomposite drain.
Design of drainage layer needs to consider clogging when
(1) High pH liquids(2) More than 2,500 g/ml of TDS or BOD
Network of perforated collection pipes (usually HDPE) carryleachate out of drainage layer.
Do not place geotextile filter directly around pipes(clogging)
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Geocomposite Drainage Layers
Geonet drainage layer between two layers of non-wovengeotextile filters.
Design is based around equivalency with granular drainage
layer, with lab testing to ensure adequate flow rates under
weight of waste.
Lab testing needs to simulate the intrusion of the geotextile
filter into the geonet core, and the compressive creep of the
geonet.
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Geonets
Bi-planar geonets commonly used in small landfills. Tri-planar geonets withstand a greater compressive stress
(important for large depths of waste).
Transmissivity under 1000 kPa can be half the
transmissivity under 100 kPa.
Use relatively high factor of safety (build up from partial
factors)
W k h N T h l i f C ff i L dfillM KL 7J l 2004
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Geotextile Filters
Pore opening size needs to be small enough to prevent fineparticles entering the geonet drainage core, whilst large
enough to allow adequate flow under compressive stress
and potential clogging.
Use a relatively high factor of safety (build up from partial
factors).
W k h N T h l i f C t ff ti L dfillM t KL 7J l 2004
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Leachate Collection and Removal
System comprises leachate filter and drainage layer,perforated collection pipes, sumps, riser pipes, pumps and
leachate storage ponds or tanks.
Sub-base must be sloping (minimum 2%).
Pipes should be spaced and sized for the required flow andmust be strong enough for the weight of the overburden of
waste (design examples given in Qian et al, 2002).
Unusually large rainstorm events can sometimes bedifficult to cope with.
WorkshoponNew Technologies forCost effectiveLandfillManagement KL 7July 2004
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Workshop on New Technologies for Cost-effective Landfill Management, KL. 7 July 2004
Geotextile Durability
ASTM test for long term immersion in leachate underelevated temperature.
Tests carried out with Hong Kong leachate indicated that
HDPE and polypropylene geotextiles had a good long term
resistance to our leachate, but polyester geotextiles had alower resistance.