130_5-leachate from sanitary landfills
TRANSCRIPT
Leachate from sanitary landfills – origin, characteristics, treatment
Assoc. Prof. Irina Kostova, Ph.D.
University of Architecture, Civil Engineering
and Geodesy
“Iskar’s Summer School” – Borovetz, 26-29 July 2006
Landfills
A landfill is defined as a system that is designed and constructed to dispose of discarded waste by burial in
land to minimize the release of contaminants to the environment.
The landfill processWhen biodegradable waste, such as paper, card and
waste food, is disposed of to the oxygen-free (anaerobic)
conditions of a landfill, breakdown by bacteria produces gas and soluble chemicals. The soluble chemicals
combine with liquids in the waste (e.g. rainwater) to form landfill leachate.
Landfill management incorporates:
•Planning;
•Design;
•Operation;
•Environmental monitoring;
•Closure;•Post closure control of landfill.
Types of landfills (according Bulgarian regulations):
I class – landfills for industrial wastes;
II class – landfill for municipal wastes;III class – landfill for hazardous wastes.
Landfills
Landfills
Advantages
• Low-cost
investments;
• Low-cost operational
needs;
• End-off utilization.
Disadvantages
• Need of large areas;
• Negative environment
impact: dust, noise,
smell, litter, insects
and animals, gas
emigration,
groundwater
pollution.
Assessment of existing landfills depending on the risks to the environment and human health
Generation of wastes 2001-2004(According to the National Statistical Institute)
industrial
municipal
hazardous
Municipal solid wastes
average – 480 kg/cap. a
Basic elements of landfills
•Siting considerations;
•Landfilling techniques;
•Cover design;
•Bottom isolation;
•Leachate treatment facilities;
•Landfill gas utilization;
•On-site operation facilities;
•Monitoring facilities.
Landfill construction
Landfill site
Clay isolation
Liner isolation
Landfill daily operation
Landfill compactor
Birds and other animals
Polluted crack
Plastic bags in trees
Landfill cloisure
Suit in flood-site
Suit in mountain terrain-site
What does it mean “leachate”? - Liquid that has seeped through solid waste in a landfill and has extracted soluble dissolved or suspended materials in the process.
It is composed of water, and organic and inorganic chemicals from the decomposition of waste.
The bacteria will degrade the waste to a state which will be relatively harmless if escape to the environment occurs. However, this can take many tens and perhaps hundreds of years.
Leachates are a potential hazardous waste from landfill sites. If not dealt with properly they can cause pollution to groundwater, health problems and effect the environment. It is important that leachates are treated and contained to prevent these occurrences.
Leachate
Precipitation
Evapotranspiration
Surface runoff
Leachate
Percolation into waste
Evapotranspiration
Leachate generation
Landfill body
Gas VentVegetative Soil
Drainage Material
Darin Pipe
Groundwater Monitoring
well
Compacted Clay
Top Liner (FML)
Bottom
Composite Liner
Upper Component
(FML)
Lower Component
(Compacted Soil)
Leachate Collection
System Sump
(Monitoring Compliance
Point)
Drain Pipes
Native Soil Foundation
Leachate Detection,
Collection, and Removal
System (LDCSR)
(i.e. Leak Detection)
Leachate Collection
And Removal System
Waste
Soil
Leachate formation
landfill
Waste material biodegradation
Waste material dissolution
Contaminated leachate
Infiltration from precipitation
LandfillLandfill
Groundwater
table Precipitation
Subsurface
water
Impervious Strata
Impervious Strata
Deep aquifer
Groundwatertable
Hydrological considerations in
landfill site
Mechanisms of leachate flow
Landfill
subgrade
Ground water
inflow
Saturated waste
Waste layer
Leachate mound
Percolation
Perched water
Leachate percloation(vadose zone)
Contaminant
transport
Recompacted barrier layer
Lateral drainage layer (optional)
Vegetation
Surface water runoff(slope)
Vegetative layer (topsoil)
Precipitation EvapotranspirationLandfill
cover
Infiltration
Surfaceleachatebreakout
Leachate
collection line
Clay
liner
Leachate flow line
Compacted solid waste
Drainage layer(2ft. or more)
Leachate
Surface water infiltration
Precipitation
RunoffRunoff
Soil liner for a sanitary landfill
Solid WasteDrainage
layer
Low
Permeable
liner
Collection
pipe
French
drain
Collection tile
Pipeline layout for leachate collection
holding tank holding tank
cleanout access
Factors affecting the composition of
landfill leachate
Type of wastes. Is it biodegradable or non-biodegradable? Is it soluble or insoluble? Organic or inorganic? Liquid or solid? Toxic or nontoxic?
Landfill conditions. The pH, temperature, degree of ongoing decomposition, moisture content, climate, and landfill age.
Characteristics of entering water. The pH, temperature, and amount.
The direction of groundwater flow. Groundwater moves slowly and continuously through the open spaces in soil and rock. If a landfill contaminates groundwater, a plume of contamination will occur. Wells in that plume will be contaminated, but other wells, even those close to the landfill, may be unaffected if they are not in the plume.
The amount of leachate produced is directly linked to the amount of precipitation around the landfill.
Leachate characteristics
Concentration (mg/L)
100 -11 000 1 000-57 000 100 – 3 500 4 - 120
Transition
phase
Years 0-5
Acid-formation
phase
Years 5-10
Methane
fermentation
phase
Years 10-20
Final
maturation
phase
>20 years
Leachate
constituent
BOD5
COD
TOC
NH4-N
NO3-N
Total diss.
solids
500 -22 000 1 500-71 000 150 – 10 000 30 - 900
100 -3 000 500 - 28 000 50 – 2 200 70 - 260
0 -190 30-3 000 6 – 430 6 - 430
0,1 - 500 0,1 - 20 0,1 – 1, 5 0,5 – 0,6
2 500 -14 000 4 000-55 000 1 100 – 6 400 1 460 – 4 640
• The anticipated flow rate that will require treatment. This mainly depends on the water inflow into the landfill.
• Composition of leachate at source which is carried out in an equipped laboratory.
• Discharge composition required by the authorities.
Factors affecting the choice of
leachate treatment
Leachate treatment options
Treatment choice
On-site treatmentDischarge or transport to off-site treatment plant
Recirculation through the landfill body
Complete treatment
Partial treatment
Discharge in surface waters
Discharge or transport to off-site treatment plant
Leachate treatment processes
Biological processes
Application Comments
Aerobic system Removal of
organics
Refractory or slowly degrading
compounds are not removed. Process
cannot tolerate influent toxics. Biological
sludge is produced. Needs separate
clarifier.
Aerated stabilization
ponds (lagoons)Removal of
organics
Requires large land area.
Fixed-film processes
(trickling filters,
biological contractors)
Removal of
organics
Temperature-sensitive in cold weather.
Cover may be needed.
Biological processes
Application Comments
Anaerobic systems
(anaerobic contractors
and lagoons)
Removal of
organics
Low operating costs and sludge
production. Requires heating. Long
detection times for high removal levels.
Typically cannot tolerate influent toxics or
high concentrations of some inorganics.
Nitrification and
denitrification
Removal of
nitrogen
Nitrification/denitrification can be
accomplished along with removal of
organics.
Leachate treatment processes
Leachate treatment processes
Physical – Chemical processes
Application Comments
Sedimentation Removal of
suspended
solids
Can remove only heavier material by
gravity. Usually used in conjunction with
other treatment processes.
Dissolved air
flotation
Dissolved contaminates are not removed.
Additional treatment is required.
Filtration Removal of
suspended
matter
Is combined with other technologies.
Useful as a polishing process.
Removal of
suspended
solids, oil and
grease
Physical – Chemical processes
Application Comments
Ultra filtration Removal of
bacteria and
high-molecular-
weight organics
Possibility of fouling. Limited applicability
to leachate.
Steam stripping Effective removals of volatile organics.
Expensive process.
Absorption Removal of
organics
Costs depend on the leachate quality.
Removal of
volatile organics
or ammonia
Leachate treatment processes
Leachate treatment processes
Physical – Chemical processes
Application Comments
Ion-exchange Removal of
dissolved organic
and inorganic
Ions of alkaline earth metals are difficult
to remove.
Neutralization Frequently used in conjunction with other
treatment.
Chemical
precipitation
Removal of
some metals,
specially Cd,
Cr, Cu, Pb, Ni
A wet sludge is produced that may
require disposal as a hazardous waste.
pH
adjustment
Physical – Chemical processes
Application Comments
Oxidation Removal of
organics.
Detoxification of
some
inorganics.
Incomplete oxidation can produce
compounds that may be more
undesirable than the parent compounds.
Complete oxidation is usually impossible.
Works well on dilute waste streams. High
oxidant demand by leachate.
Evaporation Where leachate
discharge is not
permitted
Process sludge may be hazardous.
Leachate treatment processes
Stream A
Equalization
Lime/
caustic Polymer Clarifier
Mixed
Media
filtration
Rapid
mix
Flocculation
Sludge
holding
tank
Sludge
Pressure
filter
Stream B
Equalization
Dewatered
sludge
Dirty filter
backwash
storage
Carbon
transfer
vessel
Carbon
adsorbtion
contact
vessels
Clean
backwash
and effluent
storage
Trucked
Technological scheme for chemical
treatment of the leachate
Monitoring system
direction of groundwater flow
landfill
Monitoring well
(upstream)
depth 6 m
Monitoring well
Monitoring well
(downstream)
depth 24 mMonitoring well
(downstream)
depth 12 m
Monitoring well
(downstream)
depth 30 m