What is a Landfill?

The landfill is a site used for the disposal of waste materials. The landfill is a solid waste facility that is often known as a dumping ground. The image below shows a landfill site in Hawaii. Landfilling is the most ancient and common method used for the disposal of waste. For the landfill, a deep trench is constructed in an isolated place away from the city. The trench for landfills is designed properly after analyzing the total population and the waste generation per capita. The waste is dumped into the trench and after every layer of waste, a layer of soil is spread on the top of it.

The image shows a landfill operation in Hawaii
CC BY-SA 3.0 | Image Credits: https://commons.wikimedia.org | Eric Guinther

Parts of a Landfill

A landfill structure consists of a bottom liner system, cells, stormwater drainage system, leachate collection system, methane collection system, and a cap. The bottom liner system separates the trash from the groundwater. The cells are used to store the trash in the landfill. The stormwater drainage system collects the rainwater falling on the landfill and drains it out. The leachate collection system collects the percolated water inside the landfill and the landfill leachates. The Methane collection system collects the methane gas formed inside the landfill due to the anaerobic breakdown of trash. Many landfills carry out the gas-to-energy conversion. The gases produced inside the landfills are burnt to make heat and electricity, sometimes they are purified to feed into the natural gas pipeline. The cap is provided to cover the landfill and protect it from rats, birds, or any other organism from entering the landfill.

Operation of a Landfill

The Municipal Solid Waste, Industrial waste, hazardous waste, and all other types of wastes are first collected and transported to the landfill site with the help of trucks and tippers. At the entrance of the landfill, the recyclable waste such as paper, aluminum cans, bottles, and so on is first sorted out for recycling so that the number of landfills can be reduced. The hazardous and chemical-based trash is also sorted at another station by the landfill operators. Some of the trash is then recycled and some are incinerated. The rest of the trash is then dumped into the landfills.

Types of Landfills

The landfills are classified as-

  • Municipal Solid Waste landfills
  • Industrial waste landfills
  • Hazardous waste landfills

Municipal Solid Waste landfills

Municipal Solid Waste is the daily trash discharge by the people. On average, in the USA, the amount of solid waste generation is 1.0 to 3.2 kg/per capita/day. The daily municipal solid waste includes all the household trash, garbage, ash, dust, sand, and silt. Broadly classifying, Municipal solid waste includes biodegradable waste such as kitchen waste, waste used for recycling such as paper, cardboard, glass, aluminum cans, metal substances, bottles, construction, and demolition waste, and so on, electronics waste, composite waste, and so on. Municipal Solid Waste can create nuisance and spread diseases in the surrounding. Hence, proper waste management is necessary. The waste is collected by the municipal corporation or any other local governing authority and then transported to the waste disposal site, primarily landfills.

Before solid waste landfilling, the waste is sorted by various stations and the waste to be disposed of is then dumped into the landfill. After the dumping process, the landfill is compacted with the help of large machines. Once the landfill cell is filled, it is then sealed and covered with a huge amount of dirt. In the United States, all the procedure of landfill is supervised by the Environmental Protection Agency (EPA). The design of the landfill is done in such a way that the landfill should not cause any nuisance to the surroundings and must not contaminate the surrounding. The landfills for Municipal solid waste are created in places away from the floodplains and faults.

Industrial Waste landfills

Industrial waste is the waste generated during any industrial activities. It includes the materials related to the factories, mills, manufacturing operations, and mining operations, which broadly includes scrap metals, dirt, gravels, chemicals, and so on in liquid, semi-solid or solid form. The waste generated comprises both hazardous and non-hazardous types, out of which, the hazardous waste is separated and non-hazardous is collected as industrial waste. Industrial waste in any form is hazardous to the nearby water bodies, and hence proper waste management is necessary. The industrial waste is collected as per the rules and regulations and the disposal is done in a separate landfill on the dumping site.

Hazardous Waste landfills

Hazardous wastes are the wastes that can create a threat to the people or the environment. Hazardous waste includes materials that are ignitable, reactive, corrosive, and toxic. In the United States, the supervision of hazardous waste is done as per the Resource Conservation and Recovery Act. The US government provides various tools like TOXMAP to map hazardous waste. Hazardous waste can be fatal to people and extremely dangerous to the environment. Hence, the proper waste management of hazardous waste is much necessary. The hazardous waste is first stabilized and solidified before entering the landfill and various treatments are done on it. A barrier is installed along the foundation of the landfill as extra protection to prevent hazardous waste from intervening in the ground and groundwater.

Sanitary landfilling

Sanitary landfilling is the method of disposing refuse in a landfill without creating nuisance to the public and surrounding, in a properly engineered manner. In sanitary landfill, the refuse is confined to the smallest practical area and volume and the landfilled waste is covered with a huge amount of soil after the landfilling process is completed. In sanitary landfilling, the landfill waste is filled in layers, each layer not exceeding the height of 2 meters. Each layer is then covered with 15 cm to 20 cm thick soil. The waste gets settled and stabilized in a time duration of 6 months to 2 years. The waste disposal using sanitary landfilling is done using three methods- The trench method, Area method, and Ramp method.

Context and Application

This topic is taught in graduate and postgraduate courses like:

  • Bachelors of Technology (Civil Engineering)
  • Masters of Technology (Environmental Engineering )

Practice Problems

1. Which system in the landfill separates the groundwater from the trash in the landfill?

  1. Top liner system
  2. Middle liner system
  3. Bottom liner system
  4. Adjacent liner system

Answer- c

Explanation- The bottom liner system seperates the groundwater from the trash in landfill.

2. Which of the following waste cannot be used for recycling?

  1. Glass bottle waste
  2. Paper waste
  3. Cardboard waste
  4. Kitchen waste

Answer- d

Explanation- We cannot use kitchen waste for recycling.

3. Which of the following nature of materials is not categorized under hazardous waste?

a) Toxic

b) Ignitable

c) Decomposable

d) Reactive

Answer- c

Explanation- Decomposable nature of materials is not hazardous waste.

4. What is the maximum height of each layer in sanitary landfilling?

  1. 2 meters
  2. 3 meters
  3. 4 meters
  4. 5 meters

Answer- a

Explanation- The maximum height of each layer in a sanitary landfilling is 2 meters.

5. Who supervises the landfilling operations in the United States?

  1. Environmental Protection Agency
  2. Department of Environmental Quality
  3. Department of Health Services
  4. Department of Public Health and Environment

Answer- a

Explanation- The Environmental Protection Agency supervises the landfilling operations in the United States.

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