• Journal of Korean Society of Water and Wastewater
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• v.19 no.1
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• pp.98-105
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• 2005

The effects of chlorination on the elimination of three estrogenic chemicals such as $17{\beta}$-estradiol (E2), nonylphenol (NP) and bis-phenol A (BPA) were investigated using yeast two-hybrid assay (YTA), estrogen receptor competition assay (ER-CA), and high-performance liquid chromatography/mass spectrometer (LC/MS). Results of YTA, ECA and the analysis of LC/MS indicated that the estrogenic activity of above mentioned three endocrine disruptors were significantly reduced as the result of chlorination. The decrease in estrogenic activity paralleled with decrease in estrogenic chemicals under the influence of free chlorine. One common characteristic of estrogenic chemicals is the presence of a phenolic ring. Considering that a phenolic ring is likely to undergo some sort of transformation in aqueous chlorination solution, the above mentioned results may be applied to the rest of the other estrogenic chemicals in natural waters.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.3
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• pp.211-218
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• 2015

The reaction rates of ZIRLO cladding hulls with cross-section openings were investigated using a thermo-gravimetric analysis system in order to identify whether selective recovery of Zr from oxidized cladding hulls is possible. The experimental results showed that an oxidized ZIRLO cladding hull was not reactive with chlorine gas at 400℃. However, providing fresh cross-sections on one or both ends of the ZIRLO hulls enabled a chlorination reaction. This reaction was completed after 8 hours; a 14% increase on the 7 hours seen with a bare ZIRLO cladding hull. The Sharp-Hancock plot analysis results revealed that the contracting volume model is the best for describing the reaction between the cross-section opened ZIRLO hulls and chlorine gas under the condition of this work. It was concluded that the chlorination process can be employed for oxidized ZIRLO cladding hulls by providing cross-section openings.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.825-829
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• 2012

In this study, we investigated NO oxidation characteristic that depends on available chlorine concentration and temperature of seawater which is treated by un-divided electrolysis. Reactant gas passed through bubbling reactors which is filled with electrolyzed water and then NO concentration change was analyzed. In the closed-loop electrolysis system, concentration of available chlorine increased with electrolysis time. The higher oxidation rate of NO to $NO_2$ was obtained with the higher concentration of available chlorine. Oxidation of NO was fast when temperature of electrolyzed water was high, in the case of same concentration of available chlorine.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.1
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• pp.69-75
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• 2013

The recovery of Zr from Zircaloy-4 (Zry-4) cladding hulls was demonstrated to investigate the effect of the oxidation process on the reaction rate of the chlorination reaction. In chlorination reaction experiments performed for 6 h, where reaction products were collected every 2 h, it was observed that a significant decrease in the reaction rate was caused by the oxidation process ($500^{\circ}C$, 10 h under an air atmosphere) within the reaction period of 0 - 2 h. The amount of reaction residue increased from 0.95 to 1.65wt% of initial weights in the fresh and Zry-500-10 (Zry-4 hulls oxidized at $500^{\circ}C$ for 10 h under an air atmosphere) hulls, respectively. The purity of the recovered Zr was identical at 99.61wt% for the fresh Zry-4 and Zry-500-10 hulls. Quantitative analysis of the chlorination reaction rate was performed by varying the reaction time from 0.5 to 1.0, 2.0, and 4.0 h. The fitting results showed that the relationship between weight loss and reaction time can be interpreted by a linear line with a slope of 23.35wt%/h for the fresh Zry-4 case, while two linear lines were necessary to fit the results of Zry-500-10. In addition, the slope values were 17.12 and 27.16wt%/h for (0 - 20) and (20 - 100)wt% loss regions, respectively.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.697-705
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• 2011

The aim of this study was to examine ozonation disinfection efficiency for Escherichia coli DH5alpha removal, containing the multi-resistance plasmid pB10 as well as chlorination disinfection efficiency. In addition, plasmid pB10 removal rates were estimated by ozonation and chlorination. The removal efficiency of pB10 via ozonation was about 2 to 4 times higher than chlorination. High removal efficiency of pB10 is likely due to OH radical produced during ozonation. These results suggest that integration of advanced oxidation process such as ozonation (or photocatalytic oxidation) with conventional disinfection such as chlorination may be needed for effective control of antibiotic resistant bacteria and genetic materials.

• Journal of the Korean GEO-environmental Society
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• v.13 no.4
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• pp.5-11
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• 2012

Acid mine drainage (AMD) is one of the most severe environmental problem that results from the oxidation of pyrite $(FeS_2)$ and various other metal sulfides. In this study, the influence of microorganism was tested on the process where AMD was released and the method to inhibit AMD generated by microorganisms at abandoned mine area. The activity and growth rate of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, common microorganisms affecting AMD occurrence, were measured. Chlorine dioxide $(ClO_2)$, NaCl, or surfactant (ASOR-770) was used as an inhibitor for working on activity and growth of microorganism. Among the three inhibitors, 10ppm of chlorine dioxide was the most effective inhibitor for AMD control due to the reduced the activity and growth of microorganisms by 20%.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.4
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• pp.273-279
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• 2017

Optimal processes to remove chromaticity at E water treatment plant(WTP) mainly caused by algae of E lake in Jeju island were investigated based on lab-tests of chlorine and ozone oxidation. 42.9% of chromaticity of filtered water was removed by chlorine oxidation under pH 7.0~8.0, dose of 1.0 mg/L with contact time of 30~60 min. On the other hand, chromaticity removal was 71.4% when post-ozone dose of 0.9~1.9 mg/L and pH 9.0, while it was increased to 86.7% under post-ozone dose of 3.1~7.3 mg/L and pH 9.0. However, there was no significant chromaticity removal efficiency increase when ozone doses were higher than 5.0 mg/L regardless of feeding point(i.e., pre-ozonation and post-ozonation) and pHs(i.e., 7.0 and 9.0.) under the experimental conditions. Based on the results, chlorine oxidation using existing chlorination facilities at the WTP is recommended for lower chromaticity while ozone oxidation is recommended for higher chromaticity by installing new ozone feeding facilities.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.219-226
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• 2010

In order to evaluate a removal characteristic of chloramphenicol, salicylic acid and ketoprofen according to dose of oxidants, $Cl_2$, $O_3$ and $O_3/H_2O_2$ are used as oxidants in this study. In case of that $Cl_2$ is used for oxidizing harmaceuticals, chloramphenicol, salicylic acid and ketoprofen is not removed entirely at $Cl_2$ dose rang of 0.5~5.0 mg/L for 60 min. However, removal tendency of salicylic acid is so obviously at $Cl_2$ dose higher than 1.0 mg/L. In addition, as $Cl_2$ dose and contact time increase, the removal rate of salicylic acid is enhanced. When $O_3$ is used as oxidant, chloramphenicol and ketoprofen is not eliminated at $O_3$ dose range of 0.2~2.0 mg/L. On the contrary, 30~70% of salicylic acid is removed at $O_3$ dose of 1.0~5.0 mg/L. Only 30% removal of salicylic acid is achieved at contact time of 5 min, however, the removal rate is enhanced remarkably at contact time over 10 min. In experiments using $O_3/H_2O_2$ as an oxidant, we can find that $O_3/H_2O_2$ is much more effective than $O_3$ only for removal of 3 pharmaceuticals, and the efficiency is raised according to increase of $H_2O_2$ dose. On reaction rate constant and half-life of 3 pharmaceuticals depending on $Cl_2$, $O_3$ and $O_3/H_2O_2$ dose, experiments using $O_3/H_2O_2$ show that oxidation of pharmaceuticals is less effective as the $H_2O_2/O_3$ ratio increases to above pproximately 1.0 related to reaction rate constant. An oxidation of salicylic acid by $Cl_2$ and $O_3$ particularly has a comparatively high reaction rate constant comparing $O_3/H_2O_2$, and thus salicylic acid is easily eliminated in oxidation processes.

• Korean journal of applied entomology
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• v.55 no.1
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• pp.27-33
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• 2016

Chlorine dioxide has been used as a disinfectant against microbial pathogens. Recently, its insecticidal activity has been known against stored insect pests by oxidative stress. However, any molecular target of the oxidative stress induced by chlorine dioxide has been not known in insects. This study assessed an enzyme activity of acetylcholinesterase (AChE) as a molecular target of chlorine dioxide in the Indianmeal moth, Plodia interpunctella. AChE activities were varied among developmental stages of P. interpunctella. Injection of chlorine dioxide with lethality-causing doses significantly increased AChE activity of the fifth instar larvae of P. interpunctella. Exposure of the larvae to chlorine dioxide fumigant also significantly increased AChE activity. The fifth instar larvae of P. interpunctella exhibited a negative phototaxis. However, chlorine dioxide treatment significantly interrupted the innate behavior. These results suggest that AChE is one of molecular targets of oxidative stress due to chlorine dioxide in P. interpunctella.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.3
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• pp.296-308
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• 2010

The peroxone process overcomes many of the limitations associated with conventional and advanced water treatment systems using chlorine disinfection and ozone oxidation processes. Ozone and hydrogen peroxide generate highly reactive hydroxyl free radical which oxidize various organic compounds and has highly removal efficiency. The key issue to operate peroxone process is developing the method to achieve high process effectiveness when scavengers that inhibit generation of OH radicals or consume OH radicals are co-existing in the process. Also many studies, to minimize inorganic oxidative by-products such as bromate and to reduce disinfection by-products after chlorination behind peroxone process, are needed. And we should consider the excess residual hydrogen peroxide in the water. On-line instruments and control strategies need to be developed to ensure effective and robust operation under conditions of varying load. If problems above mentioned are solved, peroxone process will be applied diversely for water treatment.