• Environmental Engineering Research
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• v.15 no.3
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• pp.149-156
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• 2010

The objective of this study was to investigate microbial removal using layered double hydroxides (LDHs) and iron (hydr)oxides (IHs) immobilized onto granular media. Column experiments were performed using calcium alginate beads (CA beads), LDHs entrapped in CA beads (LDH beads), quartz sand (QS), iron hydroxide-coated sand (IHCS) and hematite-coated sand (HCS). Microbial breakthrough curves were obtained by monitoring the effluent, with the percentage of microbial removal and collector efficiency then quantified from these curves. The results showed that the LDH beads were ineffective for the removal of the negatively-charged microbes (27.7% at 1 mM solution), even though the positively-charged LDHs were contained on the beads. The above could be related to the immobilization method, where LDH powders were immobilized inside CA beads with nano-sized pores (about 10 nm); therefore, micro-sized microbes (E. coli = 1.21 ${\mu}m$) could not diffuse through the pores to come into contact with the LDHs in the beads, but adhere only to the exterior surface of the beads via polymeric interaction. IHCS was the most effective in the microbial removal (86.0% at 1 mM solution), which could be attributed to the iron hydroxide coated onto the exterior surface of QS had a positive surface charge and, therefore, effectively attracted the negatively-charged microbes via electrostatic interactions. Meanwhile, HCS was far less effective (35.6% at 1 mM solution) than IHCS because the hematite coated onto the external surface of QS is a crystallized iron oxide with a negative surface charge. This study has helped to improve our knowledge on the potential application of functional granular media for microbial removal.

• Journal of Soil and Groundwater Environment
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• v.18 no.3
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• pp.109-118
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• 2013

Characteristics of the transport of zero-valent iron nanoparticles (nZVI) in an aquifer were investigated to evaluate an application of nZVI-based reactive zone technology. Main flow direction of groundwater was north. Preferential flow paths of the groundwater identified by natural gradient tracer test were shown northeast and northwest. The highest groundwater velocity was $4.86{\times}10^{-5}$ m/s toward northwest. When the breakthrough curves obtained from the gravity injection of nZVI were compared with the tracer curves, the transport of nZVI was retarded and retardation factors were 1.17 and 1.34 at monitoring wells located on the northeast and northwest, respectively. The ratios of the amount of nZVI delivered to the amount of tracer delivered at the two wells mentioned above were 24 and 28 times greater than that of the well on the main flow direction, respectively. Attachment efficiency based on a filtration theory was $4.08{\times}10^{-2}$ along the northwest direction that was the main migration route of nZVI. Our results, compared to attachment efficiencies obtained in other studies, demonstrate that the mobility of nZVI was higher than that of results reported in previous studies, regardless of large iron particle sizes of the current study. Based on distribution of nZVI estimated by the attachment efficiency, it was found that nZVI present within 1.05 m from injection well could remove 99% of TCE within 6 months.

• Environmental Engineering Research
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• v.14 no.1
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• pp.41-47
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• 2009

Column experiments were performed in this study to investigate humic acid adhesion to iron oxide-coated sand (ICS) under different experimental conditions including influent humic acid concentration, flow rate, solution pH, and ionic strength/composition. Breakthrough curves of humic acid were obtained by monitoring effluents, and then column capacity for humic acid adsorption ($C_cap$), total adsorption percent (R), and mass of humic acid adsorbed per unit mass of filter media ($q_a$) were quantified from these curves. Results showed that humic acid adhesion was about seven times higher in ICS than in quartz sand at given experimental conditions. This indicates that humic acid removal can be enhanced through the surface charge modification of quartz sand with iron oxide coating. The adhesion of humic acid in ICS was influenced by influent humic acid concentration. $C_cap$ and $q_a$ increased while R decreased with increasing influent humic acid concentration in ICS column. However, the influence of flow rate was not eminent in our experimental conditions. The humic acid adhesion was enhanced with increasing salt concentration of solution. $C_cap$, $q_a$ and R increased in ICS column with increasing salt concentration. On the adhesion of humic acid, the impact of CaCl2 was greater than that of NaCl. Also, the humic acid adhesion to ICS decreased with increasing solution pH. $C_cap$, $q_a$ and R decreased with increasing solution pH. This study demonstrates that humic acid concentration, salt concentration/composition, and solution pH should be controlled carefully in order to improve the ICS column performance for humic acid removal from water.

• Environmental Engineering Research
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• v.13 no.3
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• pp.141-146
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• 2008

Transport of Escherichia coli ATCC 11105 through porous media was investigated in this study using two sets of column experiments to quantify the attachment-related parameters (sticking efficiency, attachment rate coefficient and filter factor). The first set of experiments was performed in quartz sand under different ionic strength conditions (1, 20, 100, 200 mM) while the second experiments were carried out in quartz sand mixed with metal oxyhydroxide-coated sand (0, 5, 10, 25%). The breakthrough curves of bacteria were obtained by monitoring effluent, and then bacterial mass recovery and attachment-related parameters were quantified from these curves. The first experiments showed that the mass recoveries were in the range of 13.3 to 64.7%, decreasing with increasing ionic strength. In the second experiments, the mass recoveries were in the range of 15.0 to 43.4%, decreasing with increasing coated sand content. The analysis indicated that the sticking efficiency, attachment rate coefficient and filter factor increased with increasing ionic strength and coated sand content. The value of filter factor in the first experiments ranged from 1.45 e-2 to 6.72 e-2 1/cm while in the second experiments it ranged from 2.78 e-2 to 6.32 e-2 1/cm. Our filter factor values are one order of magnitude lower than those from other studies. This discrepancy can be attributed to the size of sand used in the experiment. The analysis demonstrated that the travel distance of bacteria estimated using the filter factor can be varied greatly depending on the solution chemistry and charge heterogeneity of porous media.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.1
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• pp.63-70
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• 2006

Biosorption characteristics were investigated at various temperature and pH conditions in order to establish lead(II) removal using Zoogloea ramigera 115SLR. Biosorption equilibrium isotherms and kinetics were obtained from batch experiments. The Freundlich and Langmuir model could be described the biosorption equilibrium of lead(II) on Z. ramigera 115SLR, Ca-alginate bead and immobilized Z. ramigera 115SLR. The maximum biosorption capacity of Z. ramigera 115SLR increased from 325 to 617mg $pb^{2+}/g$ biomass as temperature increased from 288.15 K to 308.15K from the Langmuir model. Fixed-bed column breakthrough curves for lead(II) removal were also obtained. For regeneration of the biosorbent, complete lead(II) desorption was achieved using 5mM HCl in fixed-bed column. This study shows the possibilities that well-treated immobilized Z. ramigera 115SLR with the mechanical intensity like TEOS (Tetraethyl orthosilicate) treatment and the optimum acid solution for desorption can be used for the effective treatment for lead(II) containing wastewater.

• Environmental Engineering Research
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• v.7 no.1
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• pp.33-37
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• 2002

The two kinds of pellet-type red-mud adsorbents (bead-type, crushed-type) were from red mud, which is generated as a by-product during the production of aluminum hydroxide from bauxite ore. The adsorption experiments of Pb^{2+} ion in the aqueous solution by these red-mud adsorbents were studied with a continuous adsorption ccolumn. As a result, the crushed-type adsorbent shows better performance in adsorption of Pb^{2+} than the bead-type adsorbent between the two types of the pellet-type adsorbents. The continusous adsorption experiment shows that the pellet-type adsorbents made from red mud have good performance for removal of Pd^{2+}. The breakthrough curves of the red-mud adsorbents were compared with that of activated carbon.

• Journal of Soil and Groundwater Environment
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• v.10 no.3
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• pp.24-31
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• 2005

This study presents a contaminant transport model suitable for a 2-dimensional heterogeneous aquifer with multiple contaminant sources. It uses a streamline simulation, which transforms a multi-dimensional problem into multiple 1dimensional problems. It runs flow simulation, streamline tracking, and calculation of contaminant concentrations by turns. The model is verificated with a Visual MODFLOW by comparing contaminant concentration distributions and breakthrough curves at an observation well. Due to its fast simulation, it can be applied to time consuming simulations such as in a fine-grided aquifer, an inverse modeling and other applications.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.263-270
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• 2016

Recent Engineered nanoparticles were increasingly exposed to environmental system with the wide application and production of nanomaterials, concerns are increasing about their environmental risk to soil and groundwater system. In order to assess the transport behavior of silver nanoparticles (AgNPs), a saturated packed column experiments were examined. Inductively coupled plasma-mass spectrometry and a DLS detector was used for concentration and size measurement of AgNPs. The column experiment results showed that solution chemistry had a considerable temporal deposition of AgNPs on the porous media of solid glass beads. In column experiment, comparable mobility improvement of AgNPs were observed by changing solution chemistry conditions from salts (in both NaCl and $CaCl_2$ solutions) to DI conditions, but in much lower ionic strength (IS) with $CaCl_2$. Additionally, the fitted parameters with two-site kinetic attachment model form the experimental breakthrough curves (BTCs) were associated that the retention rates of the AgNPs aggregates were enhanced with increasing IS under both NaCl and $CaCl_2$ solutions.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.268-268
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• 2012

Adsorption and desorption of toluene from bare and $TiO_2$-coated silica with a mean pore size of 15 nm was studied using breakthrough curves and temperature programmed desorption. Thicknesses of $TiO_2$ films prepared by atomic layer deposition on silica were < 2 nm, and ~ 5 nm, respectively. For toluene adsorption, both dry and humid conditions were used. $TiO_2$-thin film significantly improved toluene adsorption capacity of silica under dry condition, whereas desorption of toluene from the surface as a consequence of displacement by water vapor was more pronounced for $TiO_2$-coated samples with respect to the result of bare ones. In the TPD experiments, silica with a thinner $TiO_2$ film (thickness < 2 nm) showed the highest reactivity for toluene oxidation to $CO_2$ in the absence and presence of water. We show that the toluene adsorption and oxidation reactivity of silica can be controlled by varying thickness of $TiO_2$ thin films.

• Clean Technology
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• v.12 no.4
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• pp.217-223
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• 2006

The operating variables of a desorption step were experimentally investigated tor the cycle of the process made up of benzene adsorption, steam desorption, and drying step. The effect of adsorbent regeneration depending on existence and nonexistence of drying step was studied by breakthrough curves obtained in the adsorption step of the second cycle. The duration of drying step was determined by the experimental results. In case that the amount of nitrogen gas was fixed, the regeneration efficiency increased with the amount of steam. However, the effect of steam decreased as the amount of nitrogen increased. Therefore, it would be possible to predict the optimum amount of steam comparing the amount of nitrogen gas with amount of steam in economic view.