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WHAT IS A LEACHATE COLLECTION SYSTEM? Leachate is water that gets badly contaminated by contacting wastes. It seeps to the bottom of a landfill and is collected by a system of pipes. The bottom of the landfill is sloped; pipes laid along the bottom capture contaminated water and other fluid (leachate) as they accumulate. The pumped leachate is treated at a wastewater treatment plant (and the solids removed from the leachate during this step are returned to the landfill, or are sent to some other landfill). If leachate collection pipes clog up and leachate remains in the landfill, fluids can build up in the bathtub. The resulting liquid pressure becomes the main force driving waste out the bottom of the landfill when the bottom liner fails. |
WHAT ARE SOME OF THE PROBLEMS WITH LEACHATE COLLECTION SYSTEMS? Leachate collection systems can clog up in less than a decade. They fail in several known ways: 1. they clog up from silt or mud; 2. they can clog up because of growth of microorganisms in the pipes; 3. they can clog up because of a chemical reaction leading to the precipitation of minerals in the pipes; or 4. the pipes become weakened by chemical attack (acids, solvents, oxidizing agents, or corrosion) and may then be crushed by the tons of garbage piled on them. |
The main problem: The leachate collection and removal system (LCRS) is commonly the only lateral drainage system provided in a MSW landfill and serves as the primary means for leachate collection and removal. The LCRS will experience a reduction in its capacity due to compressive creep, caused by the massive weight of the garbage, and biological and chemical clogging caused by the leachate. The leachate collection system must be capable of providing adequate flow capacity for the life of the landfill. We have clearly demonstrated another important design flaw. |
Leachate is most commonly found in association with landfills where result of rain percolating through the waste and reacting with the products of decomposition, chemicals and other materials in the waste produce the leachate. If the landfill has no leachate collection system, or the system in place becomes clogged or unusable, the leachate can enter groundwater, and this can pose environmental or health problems as a result. Typically, landfill leachate is anoxic, acidic, rich in organic acid groups, sulfate ions and with high concentrations of common metal ions especially iron. Leachate has a very distinctive smell which is not easily forgotten.
The risks from waste leachate are due to its high organic contaminant concentrations and high ammoniacal nitrogen. Pathogenic micro-organisms and toxic substances that might be present in it are often cited as the most important and dangerous factors.
In older landfills, the leachate was directed to the sewers, but this caused problems. Originally one of these was the contamination by toxic metals that passed through the sewage treatment plant and eventually entered the environment.
Another problem was that if the landfill contained large amounts of organic material then methane was produced, some of which dissolved in the leachate. The most important requirement is the prevention of discharge of dissolved methane from untreated leachate when it is discharged into public sewers.
Finally, leachate can contain high concentrations of ammonia which can pose a health hazard to grazing animals, vegetation, and anything else that relies on the water table... humans for example.
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Leachate Collection
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Some Stories and Data Provided By: EJNET.ORG