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Effects of low-temperature thermal desorption (LTTD) treatment on the ecological properties of soil contaminated by petroleum hydrocarbons were assessed. For this purpose, various ecological properties related to soil health and physicochemical properties of the oil-contaminated soil before and after LTTD treatment were investigated. Total petroleum hydrocarbon concentration, electrical conductivity, organic matter, and total nitrogen decreased while water-holding capacity and available P 2 O 5 increased. The soil color was also changed but textural class was not changed after LTTD. The microbial number and dehydrogenase activity increased following LTTD, but there was no significant difference in the β-glucosidase and acid phosphatase activities. Seed germination succeeded after LTTD, but the germination rate was still lower than that in noncontaminated soil as the growth of plants and earthworms was. The results showed that overall soil health related to biological productivity and environmental functions was improved after LTTD and suggested that LTTD could be a better alternative to other harsh remediation methods. However, ecological indicators still show differences to the adjacent non-contaminated level. Therefore, to ensure safe soil reuse, the change in eco-physiochemical properties as well as contaminant removal efficiency during the remediation process should be considered.

Phytoremediation is a remediation technique that involves plant uptake, transformation, accumulation, and/or volatilization of soil- and aqueous-phase contaminants or by the stimulation of microbial cometabolic activity in the rhizosphere of the plant. Even when the principal mechanism is by stimulation of bacteria, any resultant plant contamination cannot be overlooked. For the purpose of modeling, a two-compartment plant model has been developed. The model divides the plant into the shoot compartment (which can be harvested) and the root compartment (into which contaminants can accumulate). Numerical experiments were conducted to investigate model behavior and to determine important parameters affecting plant contamination. Johnsongrass [Sorghum halepense (L.) Pers.] was used to evaluate the model behavior. The contaminants TNT (2,4,6,-trinitrotoluene) and chrysene were selected on the basis of their contrasting aqueous-phase solubilities. The results indicate that plant contamination and soil remediation by plants depend on soil properties such as soil organic carbon content, the physicochemical properties of the contaminants such as the octanol-water partition coefficient, and plant properties. The most important factor affecting plant contamination is bioavailability. As bioavailability increased, the concentrations in root and shoot compartments were predicted to increase. Microbial activities and plant contamination are closely related, which suggests that plants and microorganisms can have complementary roles in phytoremediation.

The performance of a lab-scale model biofilter system was investigated to treat CH 4 gas emitted from modern sanitary landfills using landfill cover soil as the filter bed medium. From the batch experiment to measure the influence of moisture content and temperature of the filter medium on CH 4 removal capacity of a biofilter system, the optimum moisture content and temperature were found to be 10-15% by weight and 25-35°C, respectively. From the model biofilter experiment to measure the influence of inlet CH 4 concentration and landfill gas inflow rate on CH 4 removal capacity of a biofilter system, it was found that the removal percentage of CH 4 increased as the inlet CH 4 concentration decreased. Up to a landfill gas inflow rate of 1,000 mL min −1 (empty bed retention time=7.7 min), the CH 4 removal efficiency of the biofilter was able to reach 100%. Up to CH 4 loading rate of 278.5 g CH 4 m −3 h −1 , the ratio of elimination capacity to CH 4 loading rate was 1 while they were 0.68 and 0.34 at CH 4 loading rate of 417.8 and 557.1 g CH 4 m −3 h −1 , respectively. The CH 4 removal by biofilter was also confirmed by measuring the change of temperature and moisture content of the filter medium in the model biofilter. The results demonstrated that the installation of a properly managed biofilter system should be effective to reduce atmospheric CH 4 emissions from modern sanitary landfills at the low CH 4 generation stage.

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