Solid waste management

• Physical, chemical and biological properties

of MSW (CO2-PO3)

CO2-PO4

Course outcomes Program outcome

PO3: Ability to identify, formulate and

solve engineering problems

PO4: Ability to use a system approach to

design and evaluate operational

performance

1. Have an overall understanding of

management and legislative aspects

related to municipal solid waste

services

2. Apply knowledge of science and

engineering in the design and

management of collection, transfer

and disposal of solid waste

3. Understand and discuss issues

related to solid wastes services such

as waste minimization and the

impact of this sector on society and

economy

4. Have an appreciation of issues

related to industrial and hazardous

wastes

Content of lecture

• Physical properties of MSW

• Chemical properties of MSW

• Biological properties of MSW

• Physical, chemical and biological

transformation of solid waste

Physical properties of MSW

• Specific weight @ Density

• Moisture content

• Particle size and distribution

• Field capacity

• Compacted waste porosity

All of these parameters

need to be measured

before disposal of MSW

at landfill

Recall previous lecture

Specific weight @ Density

Description

• Specific weight is defined as the weight of a material per unit volume (e.g. kg/m3 , lb/ft3 )

• Usually it refers to uncompact waste.

• It varies with geographic location, season of the year, and length of time in storage.

Significant

1. Specific weight provided information for predicting :-

• storage volume, after compaction in a collection truck and (collection of waste)

• after compaction within a landfill cell (landfill design)

Figure 1 : Type of waste with its range of weight Figure 2 : Type of compaction tools with is range

of density

Exercise

Component Density (kg/m3) Amount in sampled waste

(% by Wt)

Food waste 290 22

Mixed plastics 60 12

Glass 200 8

Ferrous and alumunium 200 12

Textiles 60 5

Dust, dirt 500 28

What is the average density of this solid waste mixture?

Answer : 254 kg/m3

During a sampling event at a tipping floor of a MRF, MSW is found to contain the

following components:

Moisture

Significant

1. It is useful for estimating heat content, landfill sizing, and transports requirements

2. It can be expressed either as a % of the wet weight or as a % of the dry weight of the material.

3. The wet-weight method is more commonly used and is expressed as follows :

M = (w-d)/w X 100

W = initial weight of sample as delivered (kg)

d = weight of sample after drying at 105oC (kg)

Definition : The moisture in a sample is expressed as percentage of the wet weight of

the MSW material

Example : Moisture content

Using the data for a MSW sample provided above, determine the average moisture content

of the sample. Base your calculations on a 100kg sample size

Solution Component Moisture content

(%)

Wt(%) Moist

weight

Dry weight

Paper waste 7 25 25 (1-0.07)(25)

Yard waste 55 18 18 (1-0.55)(18)

Food waste 65 20 20 (1-0.65)(20)

Plastic 2 5 5 (1-0.02)(5)

Wood 20 8 8 (1-0.20)(8)

Glass 3 7 7 (1-0.03)(7)

Metals 3 9 9 (1-0.03)(9)

Textile 12 8 8 (1-0.08)(8)

Total 100 72.21

Dry weight = [(moist weight)(100- % moisture]/100

Dry weight = [(100-72)/100](100%) = 28%

Particle size distribution

Field capacity (FC)

• Definition : Amount of moisture retained by mixed solids against the force gravity. Field

capacity varies with the degree of pressure applied to the waste and the state of decomposition

of the waste.

• This parameter is very critical because (1) aerobic microbial activity is optimized at/or

slightly below the field capacity (2) to predict leachate formation in landfills, compost piles,

or storage piles.

FC =0.6 – 0.55 (W/[4500 + W])

FC = % of dry weight of waste, W = overburden weight calculated at midheight of the

waste in lift (kg)

Significant of Field capacity parameter Significant of Field capacity parameter

Field capacity

Hydraulic conductivity (K) of compacted waste

• K loose sample of MSW = 15 x 10-5 m/s

• K dense baled waste MSW = 7 x 10-6 m/s

• K for shredded waste MSW = 10-4 to 10-6 m/s

Discussion How to apply knowledge of physical, chemical and biological characteristics of MSW in

Figure 1 ?

Figure 1