Minhee Lee

Heavy metal removal in groundwater originating from acid mine drainage using dead Bacillus drentensis sp. immobilized in polysulfone polymer.

Batch, column, and pilot scale feasibility experiments for a bio-sorption process using a bio-carrier (beads) with dead Bacillus drentensis sp. in polysulfone polymer were performed to remove heavy metals in groundwater originating from an acid mine drainage (AMD). For batch experiments, various amounts of bio-carrier each containing a different amount of dead biomass were added in artificial solution, of which the initial heavy metal concentration and pH were about 10 mg/L and 3, respectively. The heavy metal removal efficiencies of the bio-carrier under various conditions were calculated and more than 92% of initial Pb and Cu were found to have been removed from the solution when using 2 g of bio-carriers containing 5% biomass. For a continuous experiment with a column packed with bio-carriers (1 m in length and 0.02 m in diameter), more than 98% of Pb removal efficiency was maintained for 36 pore volumes and 1.553 g of Pb per g of bio-carrier was removed. For the pilot scale feasibility test, a total of 80 tons of groundwater (lower than pH of 4) were successfully treated for 40 working days and the removal efficiencies of Cu, Cd, Zn, and Fe were maintained above 93%, demonstrating that one kg of bio-carrier can clean up at least 1098 L of groundwater in the field.

Physical property changes of sandstones in Korea derived from the supercritical CO2-sandstone‒groundwater geochemical reaction under CO2 sequestration condition

Laboratory experiments and calculation of the dissolution constant were performed to investigate the physical property changes of sandstones in Korea resulting from the geochemical reaction of CO2 under sequestration conditions. To simulate the sub-surface storage condition (100 bar and 50 °C), the high pressurized stainless cell and chamber were used and the supercritical CO2 fluid was injected into the cell (or the chamber) by the syringe pump and the pressure regulator. Sandstone slabs and cores were used for the experiments of the supercritical CO2-sandstone‒groundwater reaction. Results of SEM/EDS and SPM analyses showed that the surface roughness of the slab increased and the precipitation of calcite, halite, and Ca-rich silicate minerals on the sandstone slab occurred during 60 days reaction, suggesting the geochemical weathering process, as a result of CO2 injection, directly leads to property changes of sandstones in a short time. The average porosity of sandstone cores as increased 8.8% with the corresponding decreases in the dry density, P and S wave velocity, dynamic Young’s modulus, and the uniaxial compression strength, indicating that the trend of property changes for the sandstone was well fitted to the first-order reaction curve. The average first-order dissolution constant (K1) of sandstones, calculated by using the loss of sandstone mass during the reaction time was 0.0000846 day−1. The K1 values will be useful for estimating the dissolution process of sandstones originated from the supercritical CO2-sandstone‒groundwater reaction while the CO2 was injected into the sub-surface.

Removal of copper and cadmium in acid mine drainage using Ca-alginate beads as biosorbent

Biosorption experiments were performed to investigate the ability of Ca-alginate beads as biosorbent for the removal of Cu and Cd in acid mine drainage (AMD). From the results of batch experiments, the removal efficiencies of both Cu and Cd for Ca-alginate beads were found to increase to 95% within 3 hours in the temperature range of 15–40 °C, indicating that it is possible to treat AMD using Ca-alginate beads within a short time period under various field conditions. For the column experiments, 381.8 g of Ca-alginate beads was packed in a Pyrex column (2.5 cm in diameter and 100 cm in height) and 119.7 liters (900 pore volumes) of AMD from the Ilgwang mine in Korea was successfully treated. The Cu and Cd removal efficiencies were maintained at levels higher than the Korean remediation goal (86% for Cu and 58% for Cd) and it was possible to treat more than 300 mL of AMD using only 1 g of Ca-alginate beads. Although AMD with a pH below 3 was injected into the column, the pH of the effluents was maintained above 3 for 1,140 pore volumes of flushing due to the buffer action of the beads. In SEM/EDS analysis of the Ca-alginate beads after the experiment, void spaces of the beads were found to be filled with precipitates of heavy metals, showing that Ca-alginate beads can be successfully used as a biosorbent for the removal of Cu and Cd in AMD.

Evaluation of Rhizofiltration for Uranium Removal with Calculation of the Removal Capacity of Raphanus sativus L.

The uranium removal capacity of radish sprouts (Raphanus sativus L.) in groundwater was calculated on the basis of the amount of uranium accumulated in the radish sprouts rather than the concentration in solution, of which process was very limited in previous studies. Continuous rhizofiltration clean-up system was designed to investigate the feasibility of radish sprouts, applying for uranium contaminated groundwater (U concentration: 110 μg/L) taken at Bugogdong, Busan. Six acrylic boxes (10 cm × 30 cm × 10 cm) were connected in a direct series for the continuous rhizofiltration system and 200 g of radish sprouts cultivars was placed in each box. The groundwater was flushed through the system for 48 hours at the constant rate of 5 mL/min. The rhizofiltration system was operated in the phytotron, of which conditions were at 25℃ temperature, 70% of relative humidity, 4,000 Lux illumination (16 hours/day) and 600 mg/L of CO2 concentration. While 14.4 L of contaminated groundwater was treated, the uranium removal efficiency of the radish sprouts (1,200 g in wet weight) was 77.2% and their removal capacities ranged at 152.1 μg/g-239.7 μg/g (the average: 210.8 μg/g), suggesting that the radish sprouts belong to the group of hyper-accumulation species. After the experiment, the sum of U amounts accumulated in radish sprouts and remained in groundwater was 1,472.2 μg and the uranium recovery ratio of this rhizofiltration experiment was 92.9%. From the results, it was investigated that the radish sprouts can remove large amounts of uranium from contaminated groundwater in a short time (few days) because the fast growth rate and the high U accumulation adsorption capacity.

The Priority Management Ranking by using the Classification of Vulnerable Areas for the Soil Contamination in Busan Metropolitan City

The purpose of this study is to highlight the National Classification System related to cleanup the soil contaminated sites and to provide some guidance to address the priority management rank system before the remediation for Busan metropolitan city. Based on the previous soil investigation data, the quantitative classification of vulnerable areas for soil pollution was performed to successfully manage the contaminated sites in Busan. Ten evaluation factors indicating the high soil pollution possibility were used for the priority management ranking system and 10 point was assigned for each factor which was evenly divided by 10 class intervals. For 16 Gu/Guns in Busan, the score of each evaluation factor was assigned according to the ratio of the area (or the number) between in each Gu (or Gun) and in Busan. Ten scores for each Gu (or Gun) was summed up to prioritize the vulnerable Gu or Guns for soil pollution in Busan. Results will be available to determine the most urgent area to cleanup in each Gu (or Gun) and also to assist the municipal government to design a successful and cost-effective site management strategy in Busan.

Surfactant-enhanced Soil Washing using Tween and Tergitol Series Surfactants for Kuwait Soil Heavily Contaminated with Crude Oil

ABSTRACT Batch experiments were performed to investigate the feasibility of a surfactant-enhanced soil washing process for soilsheavily contaminated with crude oil in Kuwait. TPH concentration of the contaminated soil was 223,754 mg/kg, sampledfrom the bottom of a vaporized oil extraction pond in the Burgan reservoir field. Commercialized eight nonionicsurfactants (Tween and Tergitol series) were used to measure the aqueous solubility for the crude oil. Among them, twoTergitol surfactants were used to evaluate the TPH removal efficiency of the surfactant-enhanced soil washing for heavilycontaminated Kuwait soil. The solubility of the crude oil in surfactant solution was in the order Tergitol 15-S-7 > Tergitol15-S-9 > Tergitol 15-S-12 > Tween-80 > Tween-20 > Tween-60, which showed that the crude oil solubilities of the Tergitolseries were higher than those of the Tween series. The TPH removal efficiencies of 2% and 5% Tergitol 15-S-9 solutionwere 59% and 65%, respectively. Because the residual TPH concentration in the washed soil was still higher than theclean-up level (10,000 mg/kg), the soil washing process was repeated five times. After the fifthwashing, the residual TPHconcentration in the soil went down to 7,680 mg/kg and its removal efficiency was 97%.Key words: Crude oil, Soil washing, Surfactant, Tergitol, Tween

Application of the Nonionic Surfactant-enhanced Soil Washing to the Kuwait Soil Seriously Contaminated with the Crude Oil

Batch experiments were performed to determine the feasibility of the surfactant-enhanced soil washing process at various washing conditions for the Kuwait soil seriously contaminated with the crude oil. The soil was sampled at a dried oil pond in Kuwait and its average TPH concentration was 223,754 mg/kg, which was too high to apply the conventional remediation process. Nine commercialized non-ionic surfactants were used for the batch experiment to measure the surfactant solubility for the crude oil because it was reported that they have worked for the soil remediation. Among them, three surfactants having high crude oil solubility were used for the soil washing experiment. From the result of batch experiment, 5% TritonX-100 washing solution showed the highest TPH removal efficiency (67%) for the crude oil contaminated soil. However, because the residual TPH concentration in the washed soil was still higher than the clean-up level in Kuwait (10,000 mg/kg), the repeated soil washing was performed. After five washings with 2% surfactant solution, the cumulative TPH removal efficiency was higher than 96% and the residual TPH concentration in the soil went down below the clean-up level. To measure the desorption capacity of TritonX-100 remained in the soil after the soil washing, the silica beads and the soil were washed five times with 2% TritonX-100 surfactant solution and then they were washed again with distilled water to detach the surfactant adsorbed on beads or soil. After five washings with surfactant solution, 7.8% and 19.6% of the surfactant was adsorbed on beads and soil, respectively. When additionally washed with distilled water, most of the residual surfactant were detached from beads and only 4.3% of surfactant was remained in soil. From the results, it was investigated that the surfactant-enhanced soil washing process with TritonX-100, Tergitol S-15-7, and Tergitol S-15-9 has a great capability for the remediation of the Kuwait soil seriously contaminated by crude oil (more than 220,000 mg/kg).