Landfill leachate composition

Jones-Lee, A. and Lee, G.F. (1993) Groundwater pollution by MSW landfill Leachate composition, detection and water quality significance. In Proceedings Sardinia 93, Fourth International Landfill Symposium, S. Margherita di Pula, Cagliari, Italy, 11-15 October,... 

Robinson, H. D. Gronow, J. R. 1993. A review of landfill leachate composition in the UK. In Sardinia 93. Proceedings of the Fourth International Landfill Symposium. CISA, Environmental Sanitary Engineering Centre, Cagliari, Italy, 821-832. 

Levels of analyzed compounds were comparable with those reported in previous studies with the exception of cadmium, ammonia, 2(3H)benzothiazolone, and bisphenol A, which were higher than the published data regarding long-term composition of MSW landfill leachate from some European MSW landfills while... 

Johnson, C. A., Kaeppeh, M., Brandenberger, S., Ulrich, A. Baumann, W. 1999. Hydrological and geochemical factors affecting leachate composition in municipal solid waste incinerator bottom ash. Part II. The geochemistry of leachate from Landfill Lostorf, Switzerland. Journal of Contaminant Hydrology, 40, 239- 259. 

Hydrological and geochemical factors controlling leachate composition in incinerator ash landfills... 

Ludvigsen, L., Albrechtsen, H. J., Ringelberg, D. B., Ekelund, F. Christensen, T. H. (1999). Distribution and composition of microbial populations in landfill leachate contaminated aquifer (Grindsted, Denmark). Microbial Ecology, 37, 197-207. 

Leachate composition varies significantly among landfills, depending on waste composition, waste age, and landfill technology. The waste can be divided into three main groups household waste, demolition waste, and chemical and hazardous waste. 

Table 1 Composition of landfill leachate. Values in mg unless otherwise stated.

Inside a landfill leachate plume the environment is characterized by the presence of reduced species and high concentrations of dissolved organic matter. This environment is partly due to the composition of the leachate from the landfill and partly due to microbial processes in the plume. Since this environment is very different from that of uncontaminated, oligotrophic, often aerobic aquifers surrounding the plume, the composition of the microbial population of the plume is dramatically different from the indigenous microbial population of the uncontaminated aquifer. 

The values are unstable and vary from 100 to 600 mg dm"3. The chemical composition of the landfill leachate is a good indicator for the waste composition and age, the operating and climatic conditions. 

More recently lEC has also been employed for the analysis of landfill leachates.Sample pretreatment steps may include centrifugation, filtration, removal of interfering organic compounds, and carbonate removal. An advantage is that these lEC methods analyze for a wider spectrum of organic acids than the GC methods, hence giving a more complete picture of the organic acid composition in landfill leachates. 

Because of the heterogeneous nature of landfill, the bacterial population and therefore gas ratios, gas production rates and leachate composition can diange from one region to the next, and can affect the landfill pollution potential. Other factors of major significance include moisture content, pH and temperature. The available surface area and the nature of the surface of refuse particles will also be important determinands of microbial activity, and will thus affect the nature of the hazard posed by landfill gas and leachate. 

The waste composition will affect both the bulk gases and the trace components, while the amount and composition of landfill leachate will be affected by both the absorbent and adsorbent capacity of the waste, and the waste composition. The leachate will be comprised of both the readily soluble components of the undegraded waste and the soluble products of waste degradation. 

The main physico-chemical processes that occur in landfill are presumed to be precipitation, adsorption, ion-exchange and volatilisation, althou very few studies of the physico-chemical processes in landfilled waste have been undertaken. Volatilisation will affect landfill gas composition, but otherwise these processes will have a major impact on the leachate composition and the associated hazard. Leachate composition and reactions will also be affected by the waste characteristics including the redox potential, adsorption characteristics, temperature and biological mechanisms. 

The composition of landfill leachate may be expected to vary with time, and from site to site, as a consequence of variable water infiltration rates and amounts, differing ages of sites, differing waste composition and local environmental conditions. The processes of leachate generation within the site have already been discussed, and the change in leachate composition as the waste moves from the acetogenic phase to the methanogenic phase have been described briefly. 

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