Overview of Landfill Leachate Containment Methods

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Overview of Landfill Leachate Containment Methods

Posted On : Sep-19-2013 | seen (1092) times | Article Word Count : 544 |

Landfill leachate containment is a key component of landfill management. Leachate is created when rain, or moisture content in trash, absorbs contaminants from the solid waste it passes through.

Landfill leachate containment is a key component of landfill management. Leachate is created when rain, or moisture content in trash, absorbs contaminants from the solid waste it passes through. Engineers employ a complicated system of liners, pumps, piping, and capping to reduce the risk of leachate leaking.

Tools for containment

An essential part of leachate control is the bottom liner of each compartment in the landfill, which prevents harmful substances from seeping into surrounding soil and groundwater. The liners may be natural, artificial, or a combination, and are often topped by a drainage blanket of coarse gravel. An example of a natural liner is clay, which has low permeability. Sodium bentonite is a commonly used artificial liner, because it can withstand corrosive chemicals found in leachate. Other artificial liners include puncture-resistant synthetic plastic, such as polyethylene, and geotextile mats. Some double liners, such as clay and synthetic, have leak detection systems, but they generally only indicate a leak in the primary liner.

To reduce leachates, landfills are kept as dry as possible by testing and regulating the moisture content of trash and diverting rainwater. Plastic drainage pipes and storm liners capture and channel rainwater from the landfill to concrete or gravel-lined drainage ditches which lead to collection ponds.

Leachates that accumulate in the landfill are pumped or drained through perforated pipes, placed throughout the landfill, into leachate pipes that connect to collection ponds. Both pipes and containment materials, for leachate, must be made of special materials, such as HDPE, to endure the acidity of leachate and prevent leakage.

Once in the containment pond, soil particles are allowed to settle and the liquid is tested for acceptable levels of chemicals, such as magnesium, iron, sulfate, and chloride. Waste water can then be recirculated into the landfill, to speed decomposition and help trap methane gas, or treated and discharged into a sanitary sewer system or surface water. This is the "sanitary landfill" approach, and requires continual maintenance if used as a long-term strategy.

Each landfill cell is covered daily with soil, tarps, or spray coverings of paper or cement/paper emulsions, which take up much less space than soil, to keep out pests and air. The final cover of a landfill is designed to keep water out, thereby reducing leachate. A polyethylene cap may be used, covered with compacted soil, and planted with certain vegetation to prevent erosion.

Types of containment

There are a couple other containment strategies that may be utilized. The "dry tomb" approach seeks to stop all water from entering after the landfill is sealed. This results in waste essentially being mummified. However, the encapsulation eventually breaks down so it is not a good long-term strategy.

In controlled containment release, the quality and/or amount of leachate is kept at an environmentally acceptable level, and controlled quantities of leachate are discharged after environmental consequences have been determined. Sloped, geologically stable caps, with a drainage system and vegetation for evapotranspiration, may be installed for long-term containment.

Each landfill is different, so the requirements for landfill leachate containment should be flexible and based on practical needs, but the goal of keeping leachate contained, so as not to endanger the environment or public health, remains the same.

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<h1>Overview of Landfill Leachate Containment Methods</h1> Author: <a href='http://www.articleseen.com/profile_Mr William Hauselberg.aspx'>Mr William Hauselberg</a> Landfill leachate containment is a key component of landfill management. Leachate is created when rain, or moisture content in trash, absorbs contaminants from the solid waste it passes through. Engineers employ a complicated system of liners, pumps, piping, and capping to reduce the risk of leachate leaking.

Tools for containment

An essential part of leachate control is the bottom liner of each compartment in the landfill, which prevents harmful substances from seeping into surrounding soil and groundwater. The liners may be natural, artificial, or a combination, and are often topped by a drainage blanket of coarse gravel. An example of a natural liner is clay, which has low permeability. Sodium bentonite is a commonly used artificial liner, because it can withstand corrosive chemicals found in leachate. Other artificial liners include puncture-resistant synthetic plastic, such as polyethylene, and geotextile mats. Some double liners, such as clay and synthetic, have leak detection systems, but they generally only indicate a leak in the primary liner.

To reduce leachates, landfills are kept as dry as possible by testing and regulating the moisture content of trash and diverting rainwater. Plastic drainage pipes and storm liners capture and channel rainwater from the landfill to concrete or gravel-lined drainage ditches which lead to collection ponds.

Leachates that accumulate in the landfill are pumped or drained through perforated pipes, placed throughout the landfill, into leachate pipes that connect to collection ponds. Both pipes and containment materials, for leachate, must be made of special materials, such as HDPE, to endure the acidity of leachate and prevent leakage.

Once in the containment pond, soil particles are allowed to settle and the liquid is tested for acceptable levels of chemicals, such as magnesium, iron, sulfate, and chloride. Waste water can then be recirculated into the landfill, to speed decomposition and help trap methane gas, or treated and discharged into a sanitary sewer system or surface water. This is the "sanitary landfill" approach, and requires continual maintenance if used as a long-term strategy.

Each landfill cell is covered daily with soil, tarps, or spray coverings of paper or cement/paper emulsions, which take up much less space than soil, to keep out pests and air. The final cover of a landfill is designed to keep water out, thereby reducing leachate. A polyethylene cap may be used, covered with compacted soil, and planted with certain vegetation to prevent erosion.

Types of containment

There are a couple other containment strategies that may be utilized. The "dry tomb" approach seeks to stop all water from entering after the landfill is sealed. This results in waste essentially being mummified. However, the encapsulation eventually breaks down so it is not a good long-term strategy.

In controlled containment release, the quality and/or amount of leachate is kept at an environmentally acceptable level, and controlled quantities of leachate are discharged after environmental consequences have been determined. Sloped, geologically stable caps, with a drainage system and vegetation for evapotranspiration, may be installed for long-term containment.

Each landfill is different, so the requirements for landfill leachate containment should be flexible and based on practical needs, but the goal of keeping leachate contained, so as not to endanger the environment or public health, remains the same.
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