| 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 , chemical oxygen demand ,
total phosphorus C TP>, ammonia nitrogen C NHJ), suspended solids
, color, pH, alkalinity, cations
and heavy metals . 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
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% , 46 % , 37% CPb), from
leaching to 71 %, and 75% (Cr) respectively. |