Browsing by Author "Mare, Pieter Willem"
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- ItemEx-situ soil washing of diesel contaminated soil using impinging stream reactors and selective soft self attrition(Stellenbosch : Stellenbosch University, 1999-12) Mare, Pieter Willem; Lorenzen, L.; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.ENGLISH SUMMARY: When considering oil spills, the focus has usually been on the pollution of water and the corresponding impact on the animals and habitat concerned. There is, however, another important aspect that has largely been neglected - soil contamination. The remediation of diesel contaminated soil, making use of soil washing techniques consisting of two technologies i.e., Impinging Stream Reactors and Selective Soft Self Attrition was studied in this project. The primary aim of these processes will be as a pre-treatment step for bioremediation in a complete treatment system, capable of reducing total remediation times considerably. The Impinging Stream Reactor (ISR) process uses a high pressure water jet to remove the diesel from the soil particles. The Selective Soft Self Attrition (SSSA) process uses a novel stirrer to stir a high density slurry (consisting of contaminated soil and water) resulting in interparticle scrubbing that removes the contaminant. Both processes were optimised with respect to all operating variables. The most important variable in soil remediation is the particle size distribution to be treated. Four samples of silica sand differing only in particle size fraction were used to represent the range from fine silty soils (42% -10 μm) to coarse sandy soils (+500μm). The Impinging Stream process was able to reduce diesel contamination levels in sandy soils by 96% (this corresponds to 2000 ppm, the most sensitive sites requiring levels below 200 ppm) but was not effective in treating silty soils. The Selective Soft Self Attrition process was able to reduce diesel contamination on sandy soils by 96% (to 2000 ppm) and silty soils by 94% (to 3000 ppm). Adding coarser sand as grinding agent to silty soils, reduces this value a further 2% (to below 2000 ppm). Analyses of the sand (after washing) were done by extracting the diesel with Methylene Chloride in a Soxhlet Extraction Unit, after which the solvent was evaporated and the residual diesel determined gravimetrically. Altering the evaporation part by slowing it down considerably, resulted in improved accuracy and repeatability. Gas chromatographic analyses of the diesel extracted from the sand was also done and showed that the components in diesel lighter than C 15 are being predominantly removed during these processes.