Leachate composition

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... 

Fig. 5. Conceptual model of hydrological and geochemical processes controlling leachate composition.

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. 

Kjeldsen P., Grundtvig A., Winther P., and Andersen J. S. (1998a) Characterization of an old municipal landhll (Grindsted, Denmark) as a groundwater pollution source landhll history and leachate composition. Waste Manage. Res. 16, 3-13. 

Tab. 3. Average Leachate Compositions from Static Leaching Experiments with Appalachian Coal Preparation Wastes...

The third leaching trend observed involved a delayed release curve in which a short (1—5-min.) period of time elapsed before the maximum concentration in the leachate was observed. The eastern Kentucky fly ash (EKY-FA) sample exhibited this trend. This leaching behavior appeared to us to be related to the morphology of this ash. Large-diameter hollow ceno-pheres dominate this sample. These particles have a smaller total surface area available for reaction with the leaching solution. Reaction times are therefore delayed or slowed down. Fig. 2 shows these three leaching trends. Leachate composition vs. whole ash composition... 

Fig. 4, Whole ash composition (solid line) vs. mean maximum leachate composition (dashed line) for selected elements in four coal ashes.

Owing to the volatility of Mn, Pb, Zn and Cu, it is assumed that these elements are released in the gaseous state during combustion and condense onto the fly ash spheres as cooling occurs (Davison et al., 1974 Kaakinen et al., 1975 Linton et al., 1976 Smith et al., 1979). Therefore, these elements make initial contact with the leaching solution. The chemical complexing of these elements and the method of adsorption and attenuation are important factors to consider when estimating leachate composition from ash composition. From the data, it is concluded that Fe is located primarily in the ash... 

Phase 1 is characterized by very high concentrations of easily soluble components such as chloride and sulfate the slag is not yet carbonatized portlandite and gypsum may influence leachate composition to some extent. 

Hazard identification (indicator chemical selection) - This may include determination of leachate composition... 

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 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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