Topic 2 : Extermination and destruction
Problems arising from used materials at present are an important reason that all parties should pay attention to and work together to solve problems because they are problems that occur in communities at all levels and are becoming more serious daily. It is due to economic growth. The population increased, and people's consumption behavior began to change. In the past, people used to use food baskets when going to the market to wrapping food with banana leaves, which are biodegradable materials. Nowadays, products with packaging such as plastic, foam, glass, paper, metal, and aluminum are increasingly being used, causing the number of materials being used to increase as well.
2.1 Material degradation time
Each biodegradable material has a different rate of degradation. Some materials have a meager rate of degradation and can naturally decompose. Nevertheless, some materials, such as glass, are not biodegradable. The rate of degradation of each type of waste is different as follows:
2.2 Disposal of used materials
There are many ways to dispose of used materials that have been used continuously from the past to the present, such as bringing them to the dump on the ground, disposed into the sea, burned outdoors, burned in an incinerator, and buried in a sanitary manner, Etc. Some of these materials are improperly disposed of, causing environmental toxicity and affecting health. Therefore, the appropriate model must be studied before selecting a method for disposing of each type of material.
Methods for proper disposal of used materials should have the following
characteristics.
(1) Do not make the used material disposal area a food source, a breeding ground for animals and disease-carrying insects such as flies, mosquitoes, and cockroaches.
(2) Do not cause contamination to water sources and ground.
(3) Do not pollute the environment.
(4) Must not be a cause for nuisance due to smell, smoke, visibility and dust
Figure 4.11 shows the time of decomposition of each type of waste.
Land dumping, dumping at sea, and outdoor burning are considered invalid waste disposal methods because they cause pollution to the environment.
Sanitary methods of disposal of materials are incineration and landfill.
Figure 4.12 Collection of Used Materials
2.2.1 Incineration
Incineration can destroy almost any material, and many types depend on the material's nature. If it is a type of material that is easily flammable, a type of furnace that does not require the help of fuel can be used. While the material has more than 50 percent moisture content, the kiln must be a type that uses fuel oil to assist in combustion. Firing in a kiln takes up little space. The remnants of the burning ashes can be used to fill land or for other purposes.
The disposal of used materials by incineration can be divided into 2 groups:
1. Combustible used materials include paper, cloth or textiles, vegetables, fruits, food scraps, plastic, grass and wood.
2. Non-combustible materials such as iron or other metals, glass, stone, tiles, shells, Etc.
Disposal of Used Material Using an Incinerator
Due to the differences and characteristics of the composition of each material, used materials are destroyed by incineration in a kiln that has been approximately designed and constructed with a burning temperature of 850 - 1,200 °C for maximum destruction.
Therefore, the form of the kiln is also different. For example, if the community has used easily flammable materials, the kiln may use a type that does not require other fuels to assist in combustion. However, if the composition of the material has less than 30% combustible content (by weight) or more than 50% moisture content, the kiln used must be a type that requires fuel to assist combustion.
In addition, all kilns must have a temperature control process. Smoke, flue, dust and ash may be mixed with the smoke and blown out through the flue. An efficient incinerator must minimize the number of used materials, and the explosion remains must be stable, non-degradable, and can be utilized safely.
Advantages of disposing of waste materials using incinerators
1. Take up less land compared to the landfill method.
2. Able to destroy almost all types of solid waste.
3. The incinerator can be built in an area not far from the waste source, saving transportation costs.
4. Not affected by climate change.
5. The residue from burning (ashes) can be used to fill the land or make construction materials.
Disadvantages of disposing of used material using an incinerator
1. The cost of investment in construction and maintenance costs are quite high.
2. There may be air pollution problems.
Figure 4.13 Incineration System
2.2.2 Landfill
Disposing of used materials by landfill is pouring used materials into a prepared area and having various systems to prevent the release of various pollutants to the outside. The next step is using a machine to spread and compact to collapse. Lastly, use soil to cover and compact again until the area is entire to prevent problems with odors, insects, animal carriers, rainwater and other nuisances.
There are three methods of landfilling used materials:
1. The flat landfill method is a landfill method that starts from the original soil level without excavating the soil to compact the material along the horizontal first. Then compacted over the next layer higher and higher to the specified level. To bury used materials by this method is necessary to build an embankment along the area's boundary that acts as a wall or edge to support compaction and prevent wastewater from decomposing materials so as not to seep outside. Space characteristics required to use this method are plain or placed with the groundwater level slightly below the surface (not more than 1 meter), which cannot burrow the soil for disposal by trenching method because it may cause contamination of wastewater from used materials into the groundwater easily. This removal method is necessary to procure soil from other places to make the embankment, resulting in higher operating costs.
Figure 4.14
The Flat Landfill Method
2. The trench landfill method is a landfill method that starts at a level lower than the original soil level by excavating the soil to the specified level and then compressing it into a thin layer overlapping until it reaches the specified level. The general depth of trenching is determined with a groundwater level of not less than 1 meter, taking into account the water level in the rainy season to prevent groundwater contamination. This kind of landfill does not need to make an embankment because the wall of the excavated trench can be used as a wall to support the material to be compacted. Therefore, there is no need to transport soil from the outside, and the excavated soil can be used as a backfill.
Figure 4.15
The Trench Landfill Method
3. Valley landfill method is a method of burying large land plots which may occur naturally or may be caused by excavations such as valleys, creeks, wells, mines, Etc. Burying methods and condensing materials in each pond may vary depending on the landscape of that area. For example, if the area of the pond is relatively flat, it may be used to dig a trench or a flat landfill, depending on the case.
Figure 4.16
Valley Landfill Method
Advantages of the landfill method
1. It is a system that is not complicated.
2. The system has good flexibility. If there is a problem, the problem can be solved on time. There is no problem with used materials left over.
3. There are no remains that need further disposal.
4. There is the ability to dispose of all types and sizes of materials, except hazardous waste and infectious waste.
5. When the landfill is complete, the original area can be renovated to make a park and sports field.
6. Gas generated from landfills can be developed to be used as fuel to generate electricity.
Disadvantages of the landfill method
1. Need a large landfill area, causing problems in providing space.
2. Far away from the community resulting in high transportation costs.
3. A large amount of soil is required.
4. During the rainy season, there may be problems and obstacles in the landfill operation.
5. It may cause problems of flies and foul smell problems if landfilling does not follow sanitary principles.
In summary, problems arising from using materials today are a significant cause of the increasing amount of used materials. Due to economic growth, population growth, production processes and consumer demands in today's society. There are several methods for disposing of used materials. However, the method of disposing of sanitary waste material accepted as the correct disposal method is incineration and landfill.