Most of us have heard about landfills but few ever think of them as anything more that holes in the ground that get filled with trash bags. Nonetheless, landfills are a little more complex than how most of us perceive of it. A landfill is a waste disposal system where waste is buried, but the waste first goes through some processing before it is buried. Landfills are some of the most common means of waste disposal and have become increasingly popular due to the hazardous effects of burning waste, which used to be the primary technique of dealing with waste disposal for many developed and developing countries.
The uniqueness of landfills is how it allows for the burying of waste, in that, it does not cause an eyesore such as is the case with dumpsites and is completely isolated from getting into contact with groundwater or the air. Landfills also provide the added advantage of providing potential sources for energy which means that they make use of the waste in ways that no other trash storage method does.
Construction of the landfill
Landfills work by going through a thorough process of evaluation first in order to determine where to put them and its lifetime operation. The criteria are as follows;
1. Area of land
The section of land for setting up the landfill needs to be large as not only is the actual landfill supposed to be sizable to pack enough waste, but also requires a lot of space for supporting structures that will be discussed further on. Environmental impact study also has to be done on the land before construction begins.
2. Composition of the bottom of the pit
The bottom of the pit needs to be as watertight as possible. This means that the bottom of the pit should be compacted tightly or the bedrock should not have cracks in it to prevent water from the pit leaking into ground water.
3. Surface flow of water
The flow of water from rain should also be studied in a bid to develop strategies to prevent runoff water from the landfill from making its way to rivers as well as the ground table. This means, landfills cannot be constructed near rivers and lakes and they require drainage systems to manage their surface water run-off.
4. Environmental impact assessment
This is to evaluate the damage that the project will have on the surrounding region as well as drawing up plans for contingencies that will help solve problems that the landfill might cause. The systems set up here are supposed to ensure the environment does not suffer too greatly while cushioning against any forms of accidents.
5. Historical and archaeological value of the site
Historical and archaeological valuation of the site has to be done to ensure the landfill site does not disturb land that is significant in any way either historically for the local people or on the basis of archaeological importance that would be lost.
How Landfill Works?
Once these requirements are established, the landfill creation process can begins and this shows exactly how the landfill works. Landfills may differ in operations, structure and how they are designed, but the following are the typical structures involved.
1. Bottom Liner system
The Bottom Liner System is the section ensuring that the trash and leachate does not drain into the ground water or sip out of the landfill and make its way to other water sources or pollute the soil. The liner is usually a durable and puncture resistant material such as polyvinylchloride about a tenth of an inch (approximately 3 millimetres) thick.
2. The Cells
This is where the actual trash gets placed. As space is a precious commodity for landfills, there is a need to be very careful with how it is packed. Cells are created to allow for the allocation of specific space resources while guaranteeing optimal usage of the given land for the landfill. The packing process is especially rigorous, requiring that each cell be filled then compacted using heavy machinery to ensure maximum use of space. The resulting trash is usually packed till it becomes airtight.
Examples of cell dimensions have them placed at 15 by 15 by 4 meters. At the top of each cell, they are packed with about 6 inches of compacted soil to ensure the cell remains airtight, preventing insect and other pest penetration into the landfill.
3. Storm Water Drainage System
This is the system maintaining the dryness of the landfill by preventing water from seeping into the system. It directs surface runoff away from the landfill as well as ensuring water does not find way into rivers untreated.
4. Leachate Collection System
This system collects leachate that eventually seeps from the landfill. While trash put into the landfill is usually checked for liquids and rejected if it’s too wet, the system still generates enough liquid referred to as leachate. This liquid contains large concentrations of hazardous materials that have dissolved in it from the landfill trash over time.
It is therefore very dangerous to have it pool anywhere unmanaged or drain off into water sources. As such, the system collects the leachate and drains it out of the landfill into a collection region where it is processed just like sewage and released safely back into the natural water ways.
5. Methane Collection System
Due to the airtight nature of the packing process, only anaerobic bacteria can survive in the landfill. These are the bacteria that do not need oxygen to survive. The bacteria break down the materials found within the landfill and produce mostly two by-products, methane and carbon dioxide.
Methane is highly flammable; therefore, letting it collect within the landfill is a dangerous option given that it might be densely packed and eventually becomes explosive. For this reason, the methane collection systems either collects the gas and use and/or sell it as a fuel source or burn it on site to reduce its concentration inside the landfill.
6. Covering or Cap
The covering cap is the last bit of material placed daily on the landfill to cover the cells. It is usually a polythene material covered in a thick layer of soil that later has trees and shrubs grown on it once the landfill is completely filled to prevent erosion. The covering is done to prevent exposure of the waste to the air, pests, and to aid on the management of bad smell.
Effects of Landfill on the Environment
Landfills can have very adverse effects on the environment, especially when improperly constructed. The major concerns include:
Leachate is the water contained in the trash that usually seeps out over time. While management during construction ensures the trash ending up in landfills is relatively dry, some liquid is inherent within the trash and thus drains out over time. This leachate has in it dissolved organic and non-organic material and minerals. It is also usually acidic. This can cause horrendous changes in the pH levels of the soil around the landfill as well as change its chemical composition.
2. Methane as a greenhouse gas
Methane gas, as previously discussed, is extremely volatile and could easily cause problems. However, its biggest contribution to the environmental problem is that, it is a greenhouse gas. In this view, methane gas could contribute to the global warming. The situation is even made worse by the possible human errors that could contribute to problems such as accidental release of the gas due to negligence.
3. Other gases similarly cause air pollution and health problems to humans
Some other gases also tend to be produced in the landfills especially when ammonia and bleach mix. These gases can cause health problems and reduce the quality of life because of the bad smell. Besides, it can be particularly dangerous because of the tendency of converting landfills into recreational parks at the end of their lifecycle.
4. Potential fire hazard
Another huge concern is the potential fire hazard that landfills pose. Poor construction of landfills could leave enough room in the structure for air to make its way in. The produced methane gas could then easily mix with the air and ignite to start a fire. The trash within the landfill could then burn, heating to very high temperature as it burns due to its construction, the same way an oven burns, with all the compacted material above and below it. Such an occurrence could make the fires very hard to put out. Furthermore, the fire could cause the leachate to spread when attempts are made to put out the fire.
5. Soil erosion and dust
During the construction of landfills, a lot of soil is disturbed that leads to increased dust in the air. Also, the dust could rise after the completion of the project if shrubs and plants are not planted appropriately on top of the cap. Moreover, soil erosion could occur during the whole process of moving dirt as well as over time as the cap on the landfill slowly gets attacked by surface water run-off and wind.