Landfill Leachate and landfill gas are the main landfill hazards which waste disposal to land imposes the environment. We will discuss both in this article. Landfill leachate is the name given to water that has passed through solid waste and contains organic and mineral contaminants. Therefore this effluent must be treated before discharge to the environment. Landfill leachate is a major concern for landfill sites located in close proximity to agricultural land, waterways and the public domain. The leachate and runoff from the site is directed to, and stored in, on-site leachate ponds. Landfill leachate is a notoriously complex substance to deal with, primarily because of its ever-changing composition. In recent years, biological treatment in Sequencing Batch Reactors (SBRs), and engineered wetland systems have proven that they can play a valuable role in leachate treatment.
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Landfill leachate is harmful for the environment if it escapes from landfills, and can even be highly toxic due to its high strength of contamination.
Generally, PAC addition after biological treatment and settlement can be used for leachate treatment, and can sometimes have a pronounced effect on organic carbon removal (BOD and COD). PAC alone is not adequate as the ammoniacal nitrogen in leachate is not removed by PAC addition.
In hot arid climates, the removal of just the organic content from a highly polluted drainage (such as landfill leachate) may not be sufficient for treatment where discharge is made to land or into a watercourse. This is because of the high concentrations of salts and other inorganic pollutants from the leachate into the natural water cycle, even at low concentrations, may lead to bio-accumulation. That is there may not be enough winter rainfall to flush the summer salt build-up away before the next spring. Such a situation would amount to a growing potential of environmental pollution in the resultant ecosystems which receive the discharge of treated leachate.
In many wetter areas however, biological leachate treatment will be perfectly adequate, and is a much lower cost option and generally uses far less energy than the more sophisticated systems used where saline build-up is a concern.
However, extracting leachate from landfills will be essential to control leachate levels and many have experienced difficulties in doing that. The fact is that landfill leachate is pretty tough to pump.". Electric centrifugal pumps continue to manage the liquids at many landfills, and do very well to keep the methane production at peak volume to realize the site's projected energy goals.
However, they do present certain concerns with regard to their design ATEX compliance and the possibility of landfill gas explosions
, and therefore most large landfill operators have moved to pneumatic leachate extraction pumping systems. These can also be very readily fitted within retro-drilled borehole wells, as combined leachate extraction and gas extraction wells.
The main landfill design standards are discussed at length and detail see also the top landfill leachate web site.
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