Question

Write a paraphrase of this:

Properties of Waste:

The characteristics of waste must be known in order to facilitate the development of waste management systems.

Ø Physical Properties

Specific Weight (Density)

· It is mass per unit volume (kg/m3)

· It is very important factor in the design of a solid waste management system like, storage, transportation and disposal, the density of solid waste varies greatly, this due to the geographical location, season and storage duration.

· And it often refers to uncompressed waste.

Moisture Content

is defined as the ratio of the weight of water (wet weight - dry weight) to the total wet weight of the waste. The maximum amount of moisture is recorded in food residues and the waste of the courtyard. Moisture content helps in generation leachate in solid waste, thus an increase in its weight and the cost of collection and transportation.

analysis Procedure:

Take a sample of the solid waste in a container and then weigh it.

Next, place the sample in the oven in a 105 ° C temperature for 24 hours.

Then take the sample out of the oven and weigh it.

Calculate the moisture content using the formula shown below:

% of Moisture = (Wet weight- Dry weight)/ (Wet weight) x 100

Particle Size and Distribution

It is necessary to know the volume and distribution of waste, this is to recover materials, especially when using trommel screens and magnetic separators.

For example, large-sized iron elements cannot be separated by a magnetic belt or drum system.

The size of waste components can be found using the following equations:

Sc = L

Sc = (L+w)/2

Sc = (L+w+h)/3

Where

Sc = size of component, mm

L = length, mm

W = width, mm

h = height, mm

Field Capacity

It is the total amount of moisture that can be kept in the waste sample subject to gravity withdrawal.

Field capacity is very important in identification the formation of leachate in landfills.

Permeability of Compacted Waste

Ø This property is important because it controls the movement of liquids and gases in the landfill, it is depends on Pore size distribution, Surface area and Porosity.

Ø Chemical Properties

Proximate analysis of flammable components of MSW includes several test:

· Moisture (drying at 105 oC for 1 h).

· Volatile flammable materials (It ignites when there is no oxygen at 950 degrees Celsius).

· Fixed carbon (combustible residue left after Step 2)

· Ash (weight of residue after the burn in an open crucible)

Fusing point of ash: The temperature at which ash is generated from burning waste will form a solid (clinker) Which will be formed by fusion and agglomeration.

fusing temperatures: 1100 - 1200 Co

Ultimate analysis (major elements)

· Includes the determination of percentage of C (carbon), H (hydrogen), O (oxygen), N (nitrogen), S (sulfur) and ash.

· Halogen selection is often included in the Ultimate analysis.

· The result are used to determine the chemical composition of organic matter in MSW they are also used to identify the appropriate mix of waste materials to achieve appropriate C/N ratios for biological conversion processes.

Energy content:

Energy content can be determined by:

By using a full scale boiler as a Calorimeter.

By using a laboratory bomb calorimeter.

By calculation.

Most of the data on the energy content of the organic components of MSW are based on the results of bomb calorimeter tests.

Answer 1

                                              In our day to day life, lot of waste is being generated out of which some can be reduced,reused,recycled in order to protect the environment. But there is also some waste which is dumped into the seas, landfills,burnt openly,fermented and used for biological digestion and so on.

                                             Keeping in view of the health aspects of people,pollution of the surroundings,proper usage of available lands etc. it is necessary to determine the physical and chemical properties of the waste before taking any steps as mentioned in the first paragraph.

First of all What is waste?

Waste - unwanted or unusable materials.

Properties of waste:

The properties of waste are to be found in order to facilitate the development of waste management systems.

PHYSICAL PROPERTIES:

Any property that is observed or measured without change in the composition of the material is known as physical property.

1.Specific Weight (Density):

• Defined as mass per unit volume and has the units of Kg/m3 in SI units.
• Density of waste is useful for storage, transportation and disposal in the solid waste management process.
• The density of waste we generally use in the MSW is at the source of generation of waste.i.e Mass of the waste at the source is found per unit volume and also it refers to uncompressed waste. i.e the waste is not compressed.
• Storage duration,geographical location,season may affect the density values.

2. Moisture content:

• Defined as the ratio of weight of water present in the waste to the total weight of the waste.
• weight of water = wet weight of the waste - dry weight( weight obtained after keeping in an oven at 105o C for 24 hours.).
• Moisture content (%) = (wet weight - dry weight ) *100 / wet weight
• The magnitude of moisture generates leachate in solid waste.(Leachate - any liquid of varied composition that drains out from a landfill.It imparts negative health effects among humans).
• Presence of moisture improves the weight of the solid waste and also the cost of collection and transportation.

3.Particle size and distribution:

• The first step in the soild waste management is the SCREENING Process. i.e all the larger particles of specific size can be removed in the earlier stages. This can be done only when the particle size distribution of the waste is known.
• The following formulae are used:

Sc= L

Sc= (L+w)/2

Sc = (L+w+h)/3

where Sc = size of the component (mm)

          L,w,h represents Length (mm), width (mm), height(mm) respectively.

4.Field Capacity:

• Field Capacity is the amount of water left in the soil after the excess water is drained out of gravity. Hence it's a very important property for identification of leachate formation in landfills.

5.Permeability of Compacted waste:

• Permeability is the ability to allow the flow of liquids or gases.
• The magnitude of premeability depends on the pore size, surface area and porosity.
• One of the important properties as it controls the flow of liquids or gases in landfill.

CHEMICAL PROPERTIES:

Any property that results in the change of composition of a material is known as the chemical property.

These properties are essential for energy conservation.

1.Proximity analysis:

Proximity analysis is performed for the determination of waster content, volatile matter, ash content,fixed carbon from the solid waste.

1.Water ( determined from the weight loss when the solid waste is dried at 105o C for 1 hour)

2. Volatile flammable materials (flammable and combustible liquids vapourise and combine with air.generally ignites when there is no oxygen at 950o C.)

3.Ash ( residue weight after the burn in an open crucible.)

4.Fixed Carbon ( 100-(% moisture content + %volatile materials +% ash) )

2.Fusing point of ash:

• Defined as the temperature at which ash is generated and forms into a solid clinker ( a result of fusion and agglomeration)
• General range : 1100 - 1200 degree celcius.

3.Ultimate analysis:

• This analysis helps in determining the chemical compostion of waste like carbon,oxygen,hydrogen,nitrogen along with moisture and ash.i.e the amount of organic matter present in the municipal solid waste.
• Halogens( 7th group of periodic table) are often included in this analysis.
• Ultimate analysis results are helpful to identify the appropriate C/N ratios for biological conversion processes.

4.Energy Content:

We know that energy is neither created nor destroyed. It is converted from one form to other.Here, in this context how much of energy is available in the solid waste is determined to convert into useful forms like electricity generation from garbage.

Energy content is determined by the following ways,

• by using full scale boiler as a calorimeter
• by using a laboratory bomb calorimeter
• by calculations ( on dry basis and ash free basis).

Out of these,most of the data for energy content is based on bomb calorimeter values.