WHAT IS A LANDFILL?
A well built landfill is a correctly crafted and engineered sunken area of ground into which wastes are put. The aim is to avoid any water-related connections from occurring between the wastes and the surrounding environment, in particular the groundwater. In short, a landfill is a basin in the ground with a lining
WHAT IS THE COMPOSITION OF A LANDFILL?
There are four critical elements in a secure landfill: a bottom liner, a leachate collection system, a cover, and the natural hydrogeologic setting. The natural setting can be selected to minimise the possibility of wastes escaping to groundwater beneath a landfill. The three other elements must be engineered. Each of these elements is critical to success.
GEOLOGY & LOCATION:
You want the geology to do two different things for you. To prevent the wastes from escaping, you want rocks as tight (waterproof) as possible. Yet if leakage occurs, you want the geology to be as simple as possible so you can easily predict where the wastes will go. Then you can put down wells and capture the escaped wastes by pumping. Fractured bedrock is highly undesirable beneath a landfill because the wastes cannot be located if they escape. Mines and quarries should be avoided because they frequently contact the groundwater.
WHAT IS A BOTTOM LINER?
This would be a soil base- It may be one or more layers of clay or a synthetic flexible membrane (or a combination of these). If the bottom liner fails, wastes will migrate directly into the environment. There are three types of liners: clay, plastic, and composite.
WHAT IS A LEACHATE COLLECTION SYSTEM?
Leachate is the liquid formed when waste breaks down in the landfill and water filters through that waste. This liquid is highly toxic and can pollute the land, ground water and waterways. 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.
