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Landfills represent the most extensively-used method to dispose of solid waste. Employed around the world, landfills produce pollution when rain or melted snow percolates through the landfill’s natural and inorganic waste. Not only do all currently open landfills produce this pollution, but even landfills that were closed long ago continue to produce leachate. It can be expected that each volume of landfill will produce anywhere from 50 to 100 gallons of leachate.
There have been many advances in waste management technology which have allowed for the effective management of landfill leachate. There has been much research and experience to prove the ability of below-landfill saturated and unsaturated attenuation zones to hold leachate from sanitary landfills.
What are Attenuation Zones?
The attenuation zone is actually a buffer that is located around the landfill. The attenuation zone’s job is to protect the landfill from contaminating the groundwater with the leachate it produces. The attenuation zone does not have a low permeability lining. As such, the leachate seeps out into permeable ground, where it is treated by the biological action of the soil. This reduces the leachate’s potential to pollute.
Location is Key
Attenuation zones are best located in areas of optimal geology, soil permeability and soil type, as these conditions will allow for the cost-free treatment of leachate. However, they are not the only determining factors. The input of hydro-geological scientists, hydrologists and engineers is required to increase the effectiveness of natural attenuation zones. If the ground located around a new and unlined landfill is suitable and the flow and level of groundwater suitable, attenuation zones can be designed into it.
What Makes Landfills Different as a Contamination Source
Landfills stand apart from other sources of groundwater contamination because of the biological, chemical and physical responses that occur once waste has become buried. All of these processes serve to increase the waste’s toxic concentration.
Typically, landfill leachate contains ammoniac nitrogen in high concentrations, as well as high recalcitrant mixtures which may contain methylene chloride and carbon tetrachloride. Non-degradable heavy metals and complex polymers can also be present in landfill leachate. When the nitrogen in living cells is converted to ammoniac nitrogen, it forms a toxic liquid that is not only harmful to most aquatic species, but also one that is long-lived.
One option to rectifying the problem of pollution plume development is to purchase property located near to the landfill for the building of an attenuation zone. Doing this ensures that no boreholes or wells are drilled that could possibly encourage the delivery of this contaminated and dangerous water.
Regular Monitoring is Crucial
Once a landfill and its attenuation zone are in place; a crucial item is the regular monitoring of water quality within the attenuation zone. This will allow for ground pollution levels around the landfill to be measured. Regular monitoring ensures that leachate saturation in the soil doesn’t migrate to areas where boreholes or wells may be located. It also allows for the monitoring of the amount of impurities which enter the areas surrounding the landfill.
The Best time to Build Attenuation Zones
Any preparations with regard to the containment of leachate and mitigation locations should be made before the building of any landfill. To ensure that proper attenuation zones are built, several factors must be considered. These are the geology and topography of the area, as well as the potential for and level of ground leaks that can be expected to reach the groundwater from the landfill. Equally important is to identify the amount and location of groundwater to protect in order to prevent contamination of nearby drinking water sources.