Physical, Chemical, and Biological Properties of MSW

Objective:

• Understand the properties commonly associated with MSW.

Goals:

• Describe the physical, chemical, and biological  properties associated with MSW.
• Perform calculations using waste  properties.

Assignments:

• Read: Textbook: Worrell & Vesilind, Solid Waste Engineering, 2^nd edition, Chapter 2 (pp. 44-56)
• Review:  MSW Properties MS-Word file available on the CANVAS Course Shell
• Review: US EPA's Volume-to-Weight Conversion Factors for Solid Waste (PDF file)
  
• Review: Example Problem (PDF file)
• CANVAS Quiz: Physical, Chemical, and Biological Properties of MSW

PHYSICAL PROPERTIES

Bulk Density

• Values:
  • 300-700 lb/yd³ as delivered, typically 500 lb/yd³
• Function of location, season, storage time, equipment used, processing (compaction, shredding, etc.)
• Used in volume calculations

How can this information be used?

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GEOTECHNICAL PROPERTIES

SOIL PHASE DIAGRAM.

Vsample=Vsolids+Vliquid+Vgas Wsample=Wsolids+Wliquid   (Wgas~0.00) V=volume, W=weight or mass

Moisture Content (MC)

• Weight or volume based
  • Weight: wt. of water/sample wt.
    • MC_wet= water/(water+solids)
    • MC_dry= water/solids
  • Volume: vol. of water/sample volume
• Values:
  • For peak methanogenesis: 50-60% (by weight)
  • As placed: 0.036-0.205 cm/cm
  • Field capacity: 0.3-0.4 cm/cm
  • Completely saturated: 0.5-0.6 cm/cm
    • Note: This range corresponds to accepted values for the porosity of MSW
• Review: Example 2-2, Note: 100 lb assumption
  • Think: The moisture content calculated in this problem was the wet moisture content (MC_wet ).  What would the dry moisture content (MC_dry ) be?
• Related Concepts:
  • Saturation (Volume of water/Volume of voids)
  • Porosity (Volume of voids/Volume of sample)
  • Void ratio (Volume of voids/Volume of solids)
  • Note: Void space can be occupied by air and/or water

Field capacity (FC)

Moisture held by capillary forces.

• Amount of water a sample can hold under free drainage conditions
• Can be expressed as a MC or % saturation
• Theoretically, no leachate produced until FC exceeded
• Used to predict leachate production and potential leachate storage
• Values:
  • 40% saturation
  • 0.3-0.4 cm/cm

Hydraulic Conductivity, K

• Sometimes refered to as permeability
• Units: Length/Time (in/hr, cm/s, m/d, etc.)
• Darcy’s Law, Q=KiA or V=Ki
• Range for MSW: 10^-3 to 10^-6 cm/s
  • Comparison values (cm/s): gravel~10^-1, sand~10^-2, clay~10^-6
• Uses:
  • Prediction of leachate production
  • Evaluation of equivalent liner systems
  • Estimation of liner leakages

CHEMICAL COMPOSITION

• Used primarily for combustion and waste to energy (WTE) calculations but can also be used to estimate biological and chemical behaviors
• Waste consists of combustible (i.e. paper) and non-combustible materials (i.e. glass)

Proximate Analysis

1. Loss of moisture (temp held at 105 C)
2. Volatile Combustible Matter (VCM) (temp increased to 950 C, closed crucible)
3. Fixed Carbon (residue from VCM)
4. Ash (temp = 950C, open crucible)

Fusing Point of Ash

• Clinker (agglomerations of carbon and metals) formation temperature, 2000 to 2200 F

Ultimate Analysis

• Molecular composition (C, H, N, O, P, etc.)

Energy Content

• Determined through lab calculations using calorimeters
• Individual waste component energy contents
• Review: Example 2-3

BIOLOGICAL PROPERTIES

Biodegradability

• Organic fraction often equated with the volatile solids (VS) content of the waste
  • However, not all organic materials are easily degradable
• Biodegradable fraction -
• Degradation produces odors
  • Hydrogen sulfide, H₂S (rotten eggs)
  • Methyl mercaptans
  • Aminobutyric acid
  • Methane is odorless.
• Attracts flies, vermin, rodents (vector