Decompostion Phase of Landfill Leachate

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I'm looking for information on what laboratory tests could be performed on landfill leachate or gas to determine what phase of degradation the waste is currently at (phase of decomposition). 

I have come across information on testing the leachate for BOD/COD ratio and the gas for methane / CO2 ratios.

I would be grateful if someone could recommend an analytical test or preferably some papers/literature on the hydrochemistry of leachate through the lifetime of a landfill site.

The waste is a made up of construction/demolition, household food, wood etc. The landfill was capped with impermeable layer approximately 12 years ago. (I am currently assessing the risk to groundwater and surface water at the site which is underlined with a discontinuous layer of peat).

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10 Answers

  1. Dear Patrick Brehery,

    To assess air pollution by decomposition products (gaseous) you can use the express method (aspirators with indicator tubes). About 20 years ago there was also a system for determining gases by express method (aspirators with indicator tubes and a probe) directly in the ground (if I'm not mistaken, at a depth up to 2 meters).
    To assess the risk of contamination of groundwater and surface water, you can join to group at Linkedin "Landfill Groundwater Monitoring" (www.linkedin.com).To assess air pollution by decomposition products (gaseous) you can use the express method (aspirators with indicator tubes). About 20 years ago there was also a system for determining gases by express method (aspirators with indicator tubes and a probe) directly in the ground (if I'm not mistaken, at a depth up to 2 meters).
    To assess the risk of contamination of groundwater and surface water, you can join to group at Linkedin "Landfill Groundwater Monitoring" (www.linkedin.com).

  2. Patrick, please contact me at johnabaker1@aol.com and will let you know of the work I did with Geosyntec while I was at WM on this very subject--how to terminate/reduce post closure care of landfills!

  4. Landfill decomposition modelling is a complex area, their are many EPA guidelines available in many Western Countries on tests from which the depth and horizon profile of the pad can be ascertained.  But the assays are just that until a competent consultant who provides the such industry with technical services for strategic management and resolution of complex environmental issues is able to interpret and advise.

    I suggest avoiding a standard, one-size-fits-all" solution as each model will require in varying degrees development of site-specific, focused, and often innovative approaches to the environmental compliance management,,,,,,,,,

  5. The actual constituents in the groundwater leachate and in the landfill gas emitting from any landfill will be a direct result of the materials originally buried there. Unless you took samples of both early in the degradation phase it will be very difficult to estimate to what degree the original constituents have degraded.  The US EPA has a lot of information available on their website for landfills. You might want to search there for data. I believe the primary methods utilized for characterizing the contaminants are GC and GC/MS to get most of the volatile and semi-volatile compounds.

    Good Luck. 

  6.  The 3 items of importance mentioned were methane, ground water, and surface water.  1. by using the RNA microbial species called Archaea there will be no methane. All organic compounds will be reduced into their elemental/nutritional state. Toxic substances will all be chelated into their non toxic state.  2. The microbes will continue to seek out "food" until it is all biodegraded.  3. When surface waters seep into the former dumpsite their will be Zero possibility of contaminating ground water used for drinking.

  7. Methan / CO2 ratio is a fast and simple analysis of the activity in the landfill

    Be a ware that oxygen concentration should be low in any case

    From my experience a 15 years old MSW ladfill has a 35% methane, still active anaerobicly

     The poloution in the leachate , acording to local regulation, is a more relevant information, rather than the decomposition state, and it may take long to have all activity in the ladfill to end

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  8. Samples must be taken and then run them through mass spectrophotometry and atomic absorption test batteries from which the analysis therein should give a pretty clear result of what you are dealing with. Next, there are data base comparison charts in the U.S. EPA Information Library which can give you the exact findings you are looking for.

  9. Oxidation is one of the two major forms of chemical reaction in a landfill. Obviously, the extent of the oxidation reactions is rather limited, in as much as the reactions depend upon the presence of oxygen trapped in the landfill when the landfill is made. Ferrous metals are the components likely to be affected.

    The second major form of chemical reaction includes the reactions that are due to the presence of organic acids and carbondioxide (CO2) synthesized in the biological processes and dissolved in water (H2O). Reactions involving organic acids and dissolved CO2 are typical acid-metal reactions . Products of these reactions are largely the metallic ions and salts in the liquid contents of the fill. The acids lead to the solubilization and, hence, mobilisation of materials that otherwise would not be sources of pollution . The dissolution of CO2 in water deteriorates the quality of the water, especially in the presence of calcium and magnesium.

    The importance of biological reactions in a landfill is due to the following two results of the reactions:

    1. The organic fraction is rendered biologically stable and, as such, no longer constitutes a potential source of nuisances.
    2.  The conversion of a sizeable portion of the carbonaceous and proteinaceous materials into gas substantially reduces the mass and volume of the organic fraction.

    Since there is variation in the composition of leachate due to the factors like waste composition, waste age, landfilling technology, leachate sample collection techniques may also influence the measured leachate quality . For example, colloids have a high affinity for heavy metals thus the concentration of heavy metals measured in a leachate sample may depend strongly on the amount of colloidal matter present in the sample and the handling of the sample. No standard protocols for sampling, filtration, and storage of leachate samples exist. The content of colloidal matter in a sample depends to a large extent on the sampling technique used [20] where samples are obtained from groundwater monitoring wells. A high pumping rate will increase the colloid content of the sample significantly , and the heavy metal concentration may also be increased. Thus leachate samples should be filtered in the field before analysis of heavy metals, especially when the sampling is done quickly. Alternatively, samples could be withdrawn under very low pumping rates and after sufficient removal of the well. Leachate samples should be maintained under anaerobic condition until they are preserved because metal solubility varies according with their oxidation stage

  10. Pat, what would help is required is the characterization of the original disposal waste to determine the original moisture content and carbon content. Dependent where you are in the world the waste will degrade at steady rate, this may be influenced by the water content in the peat and the natural drainage. The leachate is likely to be produced solely from the degrading organic matter. This requires water to initiate the process, usually rainwater (as the site is sealed with an impermeable layer this may slow down the process. Typically if you are in wet temperate climate the rate of organic degradation will be about 15% per year, if the conditions are dryer (Dry temperate conditions then this could reduce to less than 5% a year. Regards Paul

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