• Environmental Mutagens and Carcinogens
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• v.21 no.2
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• pp.118-121
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• 2001

The predictive screening of various molecular descriptors for predicting carcinogenic, mutagenic, teratogenic and alkylation activity of chlorinated disinfection byproducts (DBPs) has been investigated for the application of quantitative structure-activity relationships (QSAR). The toxicity index for 29 compounds were computed by the PASS program and active values were employed in this study. Studies show that different descriptors account for the model equation of each genotoxic endpoint and that thermodynamic descriptors significantly played a major role on prediction of endpoints of chlorinated aliphatic compounds.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.363-369
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• 2010

This study was conducted to investigate the effects of different sanitizers and contact times on storage quality and microbial growth in fresh-cut broccoli. Fresh broccoli samples were cut into small pieces, washed each for 90 s and 180 s in normal tap water (TW), $100\;{\mu}/l$ chlorinated water (CL, pH 7), electrolyzed water (EW, pH 7.2) containing $100\;{\mu}/l$ free chlorine, or $2\;{\mu}/l$ ozonated water ($O_3$). Then, samples were packaged in 30-${\mu}m$ polyethylene bags and stored at $5^{\circ}C$ for 9 days. No significant differences were observed in gas composition and color parameters ($L^*$, $a^*$, $b^*$, and hue angle) among different sanitizers with contact times. No off-odor was detected during the storage. A longer contact time was not effective in reducing microbial population, except with $O_3$ washing. $O_3$ with 90 s was not much effective in reducing microbial population compared with Cl or EW. However, samples washed with $O_3$ for 180 s observed the lowest numbers of total aerobic and coliform plate counts. The result suggested that, a longer contact time of ozone can be used as a potential sanitizer to maintain the microbial quality and safety of fresh-cut broccoli.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.78-84
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• 2013

This study was conducted in order to evaluate the removal process for long-term contamination sources including chlorinated hydrocarbons (TCE and PCE) and explosive compounds (TNT, RDX, and HMX) in underground water using a pulsed-UV system. Crystallized cells containing the contaminants were placed 10, 20, and 40 cm away from a lamp that emits pulsed-UV rays in order to examine how the removal efficiency is influenced by the distance between the source of the light and the compounds. Chlorinated hydrocarbons were completely removed in 30 minutes with a distance of 10 cm, while PCE was completely removed even with a distance of 20 cm. In the case of explosive compounds, removal efficiencies slightly varied depending on the compounds. The majority of the compounds were perfectly removed with a contact time of 10 minutes. In particular, for RDX, the results showed that complete removal was obtained within one minute, regardless of the distance from the UV source. The amount of light energy is in inverse proportion to the distance, and thus the energy reaching the compounds severely diminishes as the distance increases. Therefore, the removal efficiency decreased with increasing distance in the system.

• Journal of Microbiology and Biotechnology
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• v.29 no.1
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• pp.91-104
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• 2019

The taxonomic and functional characteristics of bacterial communities in the pre-chlorinated rapid filters and ozonated biological activated carbon (BAC) filters were compared using Illumina MiSeq sequencing of the 16S rRNA gene and community-level physiological profiling (CLPP) based on sole-carbon-source utilization patterns. Both the rapid filters and BAC filters were dominated by Rhizobiales within ${\alpha}-proteobacteria$, but other abundant orders and genera were significantly different in both types of filter. Firmicutes were abundant only in the intermediate chlorinated rapid filter, while Acidobacteria were abundant only in the BAC filters. Bacterial communities in the rapid filter showed high utilization of carbohydrates, while those in the BAC filters showed high utilization of polymers and carboxylic acids. These different characteristics of the bacterial communities could be related to the different substrates in the influents, filling materials, and residual disinfectants. Chlorination and ozonation inactivated the existing bacteria in the influent and formed different bacterial communities, which could be resistant to the oxidants and effectively utilize different substrates produced by the oxidant, including Phreatobacter in the rapid filters and Hyphomicrobium in the BAC filters. Bradyrhizobium and Leptothrix, which could utilize compounds adsorbed on the GAC, were abundant in the BAC filters. Ozonation increased taxonomic diversity but decreased functional diversity of the bacterial communities in the BAC filters. This study provides some new insights into the effects of oxidation processes and filling materials on the bacterial community structure in the biological filters of drinking water treatment plants.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.3
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• pp.265-265
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• 1998

The phase behavior of chlorinated hydrocarbon/mixed surfactants/water microemulsion systems were investigated for dry cleaning solvent properties. With appropriate surfactant mixtures, Winsor type I-III-II microemulsions were generated which is the same as hydrocarbon systems. For perchloroethylene(PCE) with mixed Tween systems, the optimum salinity(S*) decreases and the optimum solubilization parameter(o*) increases with decreas- ing HLB. For PCE with mixed Aerosol MA and ethoxylated alcohol systems, S* and o* both increase with increasing ethylene oxide moles. For dichlorobenzene(DCB) with mixed Aerosol MA and ethoxylated or propoxylated sulfate systems, S* and o* both increase with increasing ethylene oxide moles or propylene oxide moles.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.3
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• pp.365-373
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• 1998

The phase behavior of chlorinated hydrocarbon/mixed surfactants/water microemulsion systems were investigated for dry cleaning solvent properties. With appropriate surfactant mixtures, Winsor type I-III-II microemulsions were generated which is the same as hydrocarbon systems. For perchloroethylene(PCE) with mixed Tween systems, the optimum salinity(S*) decreases and the optimum solubilization parameter(o*) increases with decreas- ing HLB. For PCE with mixed Aerosol MA and ethoxylated alcohol systems, S* and o* both increase with increasing ethylene oxide moles. For dichlorobenzene(DCB) with mixed Aerosol MA and ethoxylated or propoxylated sulfate systems, S* and o* both increase with increasing ethylene oxide moles or propylene oxide moles.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.1
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• pp.88-95
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• 1998

The Electron/Hole Pair is generated when the Activation Energy produces by Ultraviolet Ray illumination to the Semiconductor. And $OH^-$ ion produces by Water Photo-Cleavage reacts with Positive Hole. As a result, OH Radical acting as strong oxidant is generated and then Photocatalytic Oxidation Reaction occurs. The Photocatalytic Oxidation can oxidize the chlorophenol to Chloride and Carbon Dioxide easier, safer and shorter than conventional Water Treatment Process With the same degree of chlorination, the $Cl^-$ ion at para (C4) position is most easily replaced by the OH radical. And then, the blocking effect of $OH^-$ ion between the $Cl^-$ ions and $Cl^-$ ions at symmetrical location is easily replaced by the OH radical. For mono-, di-, tri-chlorophenols, there is no obvious difference in decomposition rate, decomposition efficiency and completeness of the decomposition reaction except for 2,3-dichloropheno, 2,4,5-, 2,3,4-trichlorophenol. The decomposition efficiency is higher than 75% and completeness of the decomposition reaction is higher than 70%. Therefore, continuous flow photocatalytic reactor is promising process to remove the chlorinated aromatic compounds which is more toxic than non-chlorinated aromatic compound.

• Journal of Environmental Science International
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• v.14 no.5
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• pp.513-520
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• 2005

For the destruction of toxic chlorinated organic compounds, this study proposes improved supercritical water oxidation method (multistep oxidation) using sodium nitrate as an oxidizer. This method solves the problems involved in the existing supercritical water oxidation method. Multistep oxidation means that $NaNO_3$ is oxidized to $N_2\;via\;NaNO_2$ and NO. Toxic and hard to destroy organic substances like para-dichlorobenzen(4-DCBz), polychlorinate biphenyl(PCB) ware oxidized to non toxic substances in a condition, in which rapid pressure and temperature rise is restrained as much as possible. 4-dichlorobenzene(4-DCBz) and Polychlorinate biphenyl(PCB) in condition$(450^{\circ}C,\;p_w=0.25g/cm^3,\;30min)$ Was discomposed perfectly.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.676-681
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• 2005

This study was researched for disinfection by-products (DBPs) by preozonation, prechlorination and/or postchlorination. DBPs including trihalomethanes (THMs), haloacetic acids (HAAs), halonitriles, and aldehydes were analyzed by the treatment steps of prechlorination, preozonation, sedimentation, filtration, and postchlorination comparatively. THMs were detected as $52.20{\mu}g/L$ after prechlorination and decreased during sedimentation and filtration process. The HAAs and aldehydes increased more during preozonaiton than prechlorination. However, chlorinated DBPs and aldehydes increased more by postchlorination. Chlorinated DBPs formed by preozonation increased 26% more than the chlorination process. If aldehydes were included in the total DBPs, DBPs increased up to 39% by preozonation. Preozonation could increase the removal efficiency of organic carbon during the coagulation and sedimentation processes. Ozonation might produce aldehydes that are not permitted for drinking water regulations. Also, DBPs were produced by preozonation than by chlorination. These results would bring a need for alternative disinfection studies to decrease DBPs.

• Applied Microscopy
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• v.12 no.1
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• pp.23-32
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• 1982

Caulubacter is distinctive in the morphology and replication and ubiquitous in the biosphere, especially in every type of aquatic environment. In water and waste-water treatment processes, chlorine and chlorine compounds have been used as a main disinfectant throughout the world. Therefore, Caulobacter in the waters should be affected by chlorination of the waters. The objective of this study is to determine the effects of the disinfectants on Caulobacter cells and on the developmental processes of the cells. The Caulobacter swarmer cells were disinfected by chlorine at pH 7.0 minutes of the reaction with 2.0 mg/l of infected at pH 10.0. The swarmer cells treated with 2.0 or 4.0 mg/l of chlorine for 15 minutes lost their flagella and were observed by electron microscopy to be damaged on their cell surfaces, discharging some cellular materials. When the chlorinated swarmers and untreated control samples were recultivated in fresh PYE broth medium, the control swarmers multiplicated exponentially after one-hour lag phase, whereas the chlorinated swarmers extended the lag phase to about four hours. During the extended lag phase, the cells were proved by electron microscopy to be grown and be in predivisional step, but no swarmer cell was found. When the stalked cells were chlorinated, almost all the cells were observed to have their stalks broken and some cellular materials discharged. In those samples recultivated, many cells differentiated to possess an abnormally elongated stalk with several crossbands on it. This suggests that the chlorine-shocked Caulobacter cells can develope to abnormal morphology in water environments which they can survive and regrow in.