Leachate Management

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Leachate Management Powered By Docstoc
					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                    Long chain fatty
                                                                acids


             Fermentation of
                                     Valerate, Butyrate,
                                                                    Anaerobic
             Amino acids &             & Propionate                Oxidation of
                 Sugars                                              LCFA
                                        Anaerobic

Anaerobic Pathway
                                       Oxidation of
                                          Acids



                           Acetate                     Hydrogen

                 Acetotrophic                                  Hydrogenotrophic
                methanogenesis                                  methanogenesis
                                         Methane
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        Waste age
 Compaction           Landfill
 Waste composition     design/operation
 Site Hydrology       Sampling
 Cover Design          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
    Bio-        BOD/COD      COD/TOC
degradability
    Low           < 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 September 8, 2011 by Dr. Reinhart

				
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