| Summary: | 碩士 === 崑山科技大學 === 環境工程研究所 === 103 === The sources which resulted in soil pollution includes underground storage tanks, pipeline leaking, traffic accidents and illegally dumps, etc. The most influential event polluting Taiwan soil is the underground storage tanks. We kept hearing the pipeline leaking on gas stations and the spills of refinery oil. Other than the excavation of contaminated soil and the use of chemical oxidants, soil flushing will be the prevailing method for soil remediation.
This research was started from the bottle equilibrium experiment to understand the effect of different micelle concentrations of the three surfactants (SDS, Tween 80 and Triton X-100) on diesel-contaminated soils. Followed by one-dimensional soil column experiments to imitate the actual transmission situation of Light Non-Aqueous Phase Liquid (LNAPL) in soils, and then continuing with the sand box designed on the concept of two dimensions to understand the diesel transportation under the facilitation of the surfactants.
The research finds a consistent result in bottle equilibrium and column experiments in both high and low diesel-contaminated soils. Comparing to the low concentrations of diesel-contaminated soil (5,000 mg/kg), the high concentration of diesel-contaminated soil (10,000 mg/kg) demonstrates a better water flushing efficiency. The bottle equilibrium experiments shows that the removal efficiencies of both 10 CMC and 5 CMC are above 53%, and there is no significant difference between the removal efficiencies at the high concentration of diesel-contaminated soil.
Surfactant solutions of Tween 80 and Triton X-100 are used to flush the diesel-contaminated soil packed in a column. The result shows that there is no significant difference for Tween 80 to wash the low and the high concentration of diesel-contaminated soils. It was also found that as the Triton X-100 concentration increased so did the flushing efficiency. However, the cumulative amount leaching out of the high concentration diesel-contaminated soil was not two times higher than that of the low concentration. The column experiments can be used to understand the time effect of soil flushing, the result showed that the different compounds produced even at the same flushing time in difference kinds of surfactants and the concentrations. There is an obvious chromatographic phenomenon due to the surfactant flushing.
In the sand box experiments, we use different concentrations of Triton X-100 to leach the low concentration of diesel-contaminated soil. The result shows that diesel compounds flow along with the surfactant solution. The TPH concentrations sampled at high sampling points are higher than that sampled at low sampling points. It’s because of the diesel floating, the phenomenon of chromatography in sand box are apparent than that in column experiments.
In summary, this research demonstrates that the diesel-contaminated soil at bottle experiment with high removal rate cannot to used to expected the same high removal efficiency in the column and sand box experiment, so as in the real field. The flushing direction influences the removal of LNAPL in soil column experiment. Sand box experiments can fully understand the retardation effect of different compounds in diesel complex; the flushing time and space distribution are significantly different.
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