Particle size and size distribution

PHYSICAL, CHEMICAL, AND BIOLOGICAL PROPERTIES OF MUNICIPAL SOLID WASTE

Unit 4

Task 1. In pairs answer the following questions:

1. Why do you think it is important to know physical, chemical, and biological properties of MSW?

2. What physical, chemical, and biological properties of MSW do you know?

Task 2. Pay attention to the correct pronunciation of the following words.

con­tent
measurement
moisture
percentage
residue
vehicle

Task 3. Learn new words and phrases.

commingled wastes
compacted
hydraulic conductivity
leachate
permeability
poros­ity
property
to assess
toretain
trammel screen

Task 4. Translate the following words and phrases.

agglomeration	putrescible	fusion	crucible	loose
combustion	ignition	clinker	tomanage	ester

Task 5. Make up your own sentences using words and phrases from the tasks 2, 3, 4.

Task 6. Skim the text and tell what the general idea of the text is.

PHYSICAL, CHEMICAL, AND BIOLOGICAL PROPERTIES OF MUNICIPAL SOLID WASTE

The purpose of this chapter is to introduce the reader to the physical, chemical, and biological properties of municipal solid wastes and to the transformations that can affect the form and composition of MSW. These properties must be known to develop and design integrated solid waste management systems.

PHYSICAL PROPERTIES

Important physical characteristics of MSW include specific weight, moisture con­tent, particle size and size distribution, field capacity, and compacted waste poros­ity.

Note, that the fundamentals of analysis presented in this chapter are applicable to all types of solid wastes.

Specific Weight

Specific weight is defined as the weight of a material per unit volume (e.g., lb/ft³, lb/yd³). Because the specific weight of MSW is often reported as loose, as found in containers, uncompacted, compacted, and the like, the basis used for the reported values should always be noted. Specific weight data are often needed to assess the total mass and volume of waste that must be managed. Unfortunately, there is little or no uniformity in the way solid waste specific weights have been reported in the literature. Frequently, no distinction has been made between uncompacted or compacted specific weights.

Because the specific weights of solid wastes vary markedly with geographic location, season of the year, and length of time in storage, great care should be used in selecting typical values. Municipal solid wastes as delivered in compaction vehicles have been found to vary from 300 to 700 Ib/yd³; a typical value is about 500 Ib/yd³.

Moisture Content

The moisture content of solid wastes usually is expressed in one of two ways. In the wet-weight method of measurement, the moisture in a sample is expressed as a percentage of the wet weight of the material; in the dry-weight method, it is expressed as a percentage of the dry weight of the material. The wet-weight method is used most commonly in the field of solid waste management.

Particle size and size distribution

The size and size distribution of the component materials in solid wastes are an important consideration in the recovery of materials, especially with mechanical means such as trammel screens and magnetic separator

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