Transcript Leachate Management

Landfill Processes
Objectives
Describe the physical, chemical, and
biological processes occurring in a
landfill
Describe leachate quality (Table 4-3)
Describe leachate quantity
Discuss leachate management
Degradable particulate organic material
(Proteins Carbohydrates
and
Lipids)
Hydrolysis
Inert Soluble
Amino Acids & Sugars
Fermentation of
Amino acids &
Sugars
Long chain fatty
acids
Valerate, Butyrate,
& Propionate
Anaerobic
Oxidation of
LCFA
Anaerobic
Oxidation of
Acids
Anaerobic Pathway
Acetate
Acetotrophic
methanogenesis
Hydrogen
Methane
Hydrogenotrophic
methanogenesis
Stabilization Phases – Phase I:
Initial Adjustment
Initial waste placement
Preliminary moisture accumulation
Initial subsidence
Closure of landfill area
Stabilization Phases – Phase
II: Transition
Field capacity exceeded
Leachate formed
Electron acceptor shifts from oxygen to
nitrates to sulfates
Trend toward reducing conditions
Volatile acids appear
Stabilization Phases – Phase
III:Acid Formation
Volatile fatty acids predominate in
leachate
pH declines
Substrate conversion occurs
Stabilization Phases – Phase
IV:Methane Fermentation
Methane and carbon dioxide production
pH at minimum
Nutrient consumption
Precipitation of metals
Leachate BOD/COD declines
Stabilization Phases – Phase
V:Final Maturation
Biological dormancy
Nutrients limiting
Gas production ceases
Oxygen slowly reappears
Humic substances produced
Importance of Leachate Quality
and Quantity Determination
Design leachate collection systems
Design leachate treatment facilities
Determine acceptability of offsite
treatment
Estimate offsite migration potential
Factors Affecting Leachate
Quality and Quantity
 Particle size
 Compaction
 Waste composition
 Site Hydrology
 Cover Design
 Waste age
 Landfill
design/operation
 Sampling
procedures
 Interaction of
leachate with
environment
BOD/COD Ratio
Relative biodegradability of leachate
Present for as long as 100 years
Tends to decline following onset of
methane formation
Relative Biodegradability of
Leachate
Biodegradability
Low
BOD/COD
COD/TOC
< 0.5
<2
Medium
0.5 – 0.75
2–3
High
> 0.75
>3
Nitrogen/Phosphorus
Indication of nutrient availability
Phosphorus may be limiting nutrient
Ammonia important buffer
Nitrogen present for long periods of
time
May control length of post closure care
period
pH
 Influence chemical and biological processes
of precipitation, redox, sorption,
methanogenesis
 Controlled by volatile acids during acid phase
 After methanogenesis begins, controlled by
carbonates and ammonia
 Major factor in controlling metal solubility
Heavy Metals
May act as inhibitors of biological
stabilization process
Water quality concerns
No discernable chronological pattern
Leachate concentration controlled by
sulfide, carbonate, chloride, and
phosphate
Leachate Quantity Estimation
Percent of Precipitation
Water Balance Technique (Figure 4-4)
HELP
Quasi 2-D deterministic computer-based
water budget model
Performs daily sequential analyses to
generate daily, monthly and annual
estimates of water routing
Purpose
To permit evaluators and landfill
designers wit a tool to rapidly evaluate
and compare the performance of
alternative landfill designs
Limitations
 Model does not account for surface water run
on from outside landfill area
 Model does not account for cracks in soil
 Model does not account for vegetative
species other than grass
 Model considers a wetting front
 Does not model aging of liner
 Requires extensive use of default parameters
Leachate Management Design
Steps
Layout management scheme
Select leachate removal technique
Size pump
Select storage
Select treatment and disposal
Leachate Storage
Underground storage tanks
Lagoons
Above ground tanks
three day’s storage at peak annual flow
Storage
Leachate Treatment/Disposal
On site
– biological
– chemical
– evaporative
– physical
Off-site treatment
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Last updated July 16, 2015 by Dr. Reinhart