| Abstract | This thesis is concerned with . mechanisms of contaminant
attenuation in laboratory experiments on soil-landfill leachate
contact. Six soils from three different places were filled in
seven columns (1m deep and 9. 8cm diameter). Sieve analysis and
pipette testing revealed that the soil types ranged from sand to
clay. A medium- strength leachate from municipal solid wastes in
a dumping site <COD 3086 mg/L) was allowed to pass through the
soils and contaminant reduction during passage was measured.
Column influents and effluents were monitored with respect
to total organic carbon <TOC>, chemical oxygen demand <COD>,
total phosphorus C TP>, ammonia nitrogen C NHJ), suspended solids
<SS>, color, pH, alkalinity, cations <C a, Mg, Na, K, Fe and Mn>
and heavy metals <Cd, Cu, Ni, Pb, ยท Zn and Cr). Removal capacities
for the soil types were developed based on the soil column
experiments. The column effluents were continuously analyzed for
these elements and data were correlated with soil physical and
chemical properties. Although the relative mobilities of these
elements are quite variable, data are presented showing that it
should be possible to qualitatively predict the migration of an
element on the basis of soil properties.
Adsorption processes including ion exchange were the most
activity of the mechanisms considered. They influenced the
removal of most cations presents as well as organic matter <TOC
and COD>. The average TOC removal efficiencies for column 1 to
column 7 were 46%, 66%, 26%, 48%, 68%, 60%, and 92% respectively.
The release of Ca 2 + and Mg 2 + during contact identified the
existence of ion exchange. The four cations <Ca, Mg, Na and Mn>
showed the leaching phenomenon for all columns except column 3
within the experiments. The average removal efficiencies of
potassium (iron> for column 1 to column 7 were 14% <49%), 30%
(69%>, 9% (31%>, 45% (leaching), 82% (83%), 56% <66%), and 97%
( 81 %> respectively,
Filtration functioned to remove small amounts of suspended
solids in the leachate and any precipitates formed. The removal
efficiency of SS was nearly to 97. 5% for all columns. Under
lower pH, exchange-adsorption was the dominant removal mechanism
for the metal cations, and as the pH increased, precipitation
became a more significant removal mechanism. The average removal
efficiencies of the six heavy metals for the columns were 1 4%
(Cd>, from leaching to 87% <Cu>, 46 % <Ni>, 37% CPb), from
leaching to 71 %, and 75% (Cr) respectively. |
