The Characteristics and Impacts of Landfill Leachate

Characteristics and Impacts of Landfill Leachate: Is an important publication for all landfill design professionals, encompassing a wide range of landfill leachate types and issues across varied landfill situations. Read more below:.

“An important publication for landfill designers”

Image shows the characteristics-and-Impacts of Landfill Leachate book cover.Disposing of solid waste to sanitary landfills is without doubt the lowest cost method of managing waste.
However, landfills pose a very real pollution threat to both ground and surface water resources.

Nevertheless,, top quality design and specification of landfill liners (when combined with the very best in sanitary landfill management practices), will reduce the impact of water contamination by landfills.

Unfortunately, as this book shows, unless landfill sites are lined and capped, their impact on the groundwater is very often substantial.

Chemical analysis of groundwater beneath and near two landfills from New Zealand and Lesotho (in Southern Africa) has been characterised.

This publication shows that typically there are higher concentrations of chemicals such as Chlorides, TDS and COD than average, below the landfill or in streams nearby, than in groundwater elsewhere. This is also shown near a landfill where a leachate polluted groundwater migration plume has developed.

This can occur in the vicinity of even the best operated landfills, when they are not carefully lined, to a high quality specification.

The water was also found to contain higher amounts of heavy metals. These are just some of the characteristics and impacts of landfill leachate.

How does this cause problems?

The authors explain how high concentrations of chemical constituents, such as those found in leachate contaminated water are liable to cause health complications in humans if consumed. Examples are given.

Image shows the Karawatha Forest Toxic Sewer: A visual impact of landfill leachate
The visual impact of landfill leachate is plain to see when it enters local watercourses. – CC BY-ND by sharmainedebordeaux1

The authors conclude that in order to minimise possible hazards due to landfill leachate, all future landfills do need to be lined at the base and sides.

Developers must show how this can be achieved, without causing leachate escape, by a combination of:

  • clay,
  • geosynthetic clay, and
  • high-density polyethylene liners.

Who is this Book for?

This publication would not be applicable to students and professionals within nations, such as throughout Europe, and nations that have already followed EU practices in landfill engineering, where sites have been required by environmental regulations, for many years already to be lined.

However, for those in nations where landfills remain and are planned that are unlined, the authors’ explanations of the polluting effects which occur when landfill sites are not lined and capped are given.

This leads on to highlighting the characteristics and impacts of landfill leachate . So, this will be useful reference material for all those that need to know the potential effects of leachate in the local environment around landfills.

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More About the Characteristics and Impacts of Landfill Leachate

Impacts of Leachate Release and Migration

A release of leachate to the groundwater may present several risks to human health and the environment. The release of hazardous and nonhazardous components of leachate may render an aquifer unusable for drinking-water purposes and other uses. Leachate impacts to groundwater may also present a danger to the environment and to aquatic species if the leachate-contaminated groundwater plume discharges to wetlands or streams.

Image shows the visual impact of foam and rust from leachate in a ditch. A very visible impact of landfill leachate.
Landfill leachate at a place called Maendy, UK, the orange froth is a vile mixture of solvents, phenols and other nasties from a dump created back in the day before such things had any regulation. – CC BY-NC-ND by richie rocket

Once leachate is formed and is released to the groundwater environment, it will migrate downward through the unsaturated zone until it eventually reaches the saturated zone . Leachate then will follow the hydraulic gradient of the groundwater system.

Monitoring wells at landfills allow scientists to determine whether contaminants in leachate are escaping into the local groundwater system. The wells are placed downgradient of the landfill at appropriate depths and at various intervals to intercept any contaminants and monitor their movement.

A number of forces may act on or react with the migrating leachate, resulting in changes of chemistry and a general reduction of strength from the original release. These forces are physical (filtration, sorption, advection, and dispersion), chemical (oxidation-reduction, precipitation-dissolution, adsorption-desorption, hydrolysis, and ion exchange), and biological (microbial degradation). The extent of these reactions depends on the materials underlying the landfill, the hydraulics of the groundwater system, and the chemistry of the leachate.

Although many of these reactions have the capability to reduce the potential impact to groundwater, some (such as microbial degradation) can actually increase the toxicity by producing by-products that are more hazardous than the original contaminant. This can be seen, for example, in the creation of vinyl chloride from the degradation of trichloroethene. via

The main direct impact on society of un-controlled leachate release and migration, is often that the water within the leachate contamination plume/ local surface watercourses cannot be used as drinking water, unless purified by water treatment first.

Leachate Characterization

There are three very important leachate indicator parameters which are used as indicators to identify leachate contamination in any water sample analysed in a water quality laboratory.

When people refer to high strength leachate they are normally referring to the landfill leachate from a sanitary landfill which has percolated slowly through the waste. That is leachate and has been extracted by the leachate collection and pumping system.

Image shows characteristically rusty looking leachate.
CC BY-NC-ND by jschoen2000

Landfill leachate composition for United Kingdom Landfills was first published in the Waste Management Papers published by the UK Department of Environment. Waste Management Paper 26 contains the most recent table of Landfill Leachate Composition before the WMP series was superseded by later documents, notably the DoE’s Leachate Report of 1995. via

The physical appearance of leachate when it emerges from a typical landfill site is a strongly odoured black-, yellow- or orange-coloured cloudy liquid. The smell is acidic and offensive and may be very pervasive because of hydrogen-, nitrogen- and sulfur-rich organic species such as mercaptans.

Leachate is characterized by elevated organic and inorganic contamination. Parameters measured which show significant contamination in leachate samples are pH, Sulphate, Nitrate, Nitrites, Heavy metals (Pb, Zn, Ni, Cr, CO, Fe, Mn, Cu).

Leachates of the methanogenic phase, are usually on the alkaline side of neutral when the pH value is recorded. The concentration of physio-chemical and organic contaminant parameters are found above the W.H.O standards required for drinking water, in leachate.

However, the highest of the contaminants in methanogenic stage leachate which is characteristic leachate are the COD (often in the range 500 mg/l to 10,000 mg/l), and the Ammoniacal Nitrogen concentrations (often in the range 500 mg/l to 3,500 mg/l).

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