• Research in Plant Disease
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• v.12 no.3
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• pp.272-277
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• 2006

Recycled irrigation water is a primary inoculum source of Phytophthora spp. and is capable of spreading propagules throughout nursery cultivation. Ozonation is commonly used to disinfest the recycled irrigation water; however, ozone has not been fully researched as a disinfectant for this purpose. In this study, zoospores of four species of Phytophthora were exposed for $1{\sim}9$ min to free available ozone at $0.1{\sim}0.3,\;0.5{\sim}0.7,\;0.9{\sim}1.2,\;1.4{\sim}1.7\;and\;1.9{\sim}2.2mg/l$. Zoospores, mycelial fragments, and culture plugs of P. nicotianae also were exposed to ozone concentrations ranging from 0.1 to 2.2 mg/l for periods ranging from 1 to 9 min. In addition, ozonated water was assayed monthly in 2004 and 2005 at two commercial nurseries, and quarterly in the first year at two other nurseries in Suwon, for ozone and survival of pythiaceous species using a selective medium. No zoospores of any species tested survived endpoint free ozone at 1.4 mg/l while limited mycelial fragments of P. nicotianae survived at 1.9 mg/l, and mycelial plugs treated at the same level of ozone were able to produce few sporangia. Phytophthora spp. were recovered only from nursery irrigation water with levels of free ozone at 0.3 mg/l or lower. The results of this study are essential for improving current ozonation sterilization.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.2
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• pp.113-119
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• 2011

The study purpose was to examine an effect of zero emission of excess sludge on biological reactor and treated water quality within the biological reactor in the process of biological treatment combined with excess sludge reduction system with ozone. Under an ozone injection rate 0.03 g $O_3/g$ SS, Sludge Disintegration Number (SDN) 3 and less than pH 4 as pre-treatment process, it was possible to maintain a stable biological treatment process without sludge disintegration. In the test of $OUR_{max}$, of sludge, its value was hardly under the condition of ozone injection rate 0.03 g $O_3/g$ SS. There were almost no changes of MLVSS/MLSS within biological reactor followed by a solubilization of excess sludge. Accumulation of microorganism within biological reactor was also not observed. After solubilization of excess sludge, an increase for organic matter and SS concentrations of an effluent was not observed and T-N concentration was reduced by increasing nitrification and denitrification rate within biological reactor. Most of T-P was not removed by zero emission of excess sludge and was leaked by being included in effluents.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.8
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• pp.1070-1075
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• 2006

Food materials for kimchi manufacturing were treated by ozone or gamma irradiation to reduce the number of contaminated microorganisms before the manufacturing of kimchi. Counts of total aerobic bacteria, yeast and mold were $10^6{\sim}10^7 and 10^3{\sim}10^4\;CFU/g$ in the food materials, respectively. After treatment with ozone $(3{\sim}6\;ppm), the total aerobic bacteria were reduced to 1 log cycle or more, in a dose-dependent manner. In comparison, gamma irradiation was superior to ozone treatment. Especially, irradiation of 5 kGy fully eliminated the yeast and mold attached in the food materials for kimchi manufacturing. The contents of ascorbic acid and total and reducing sugar were not affected by ozone or gamma irradiation. Taken together, it is suggested that microorganisms contaminated on materials for kimchi manufacturing could be substantially reduced by ozone (up to 6 ppm) and gamma irradiation (up to 5 kGy), without effect on the nutritional contents.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.4
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• pp.481-491
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• 2015

The aim of this study was to evaluate the chemical quenching system for residual ozone and to determine the operating condition for the quenching system. Hydrogen peroxide ($H_2O_2$) and sodium thiosulfate ($Na_2S_2O_3$) were investigated as quenching reagents for ozone removal, and the tendency of each chemical was notably different. In the case of $H_2O_2$, the degradation rate of ozone was increased as the concentration of $H_2O_2$ increase, and temperature and pH value have a significant effect on the degradation rate of ozone. On the other hand, the degradation rate of ozone was not affected by the concentration of $Na_2S_2O_3$, temperature and pH value, due to the high reactivity between the ${S_2O_3}^{2-}$ and ozone. This study evaluates the decomposition mechanism of ozone by $H_2O_2$ and $Na_2S_2O_3$ with consideration for the water quality and reaction time. Furthermore, the removal test for the quenching reagents, which can be remained after reaction with ozone, was conducted by GAC process.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.2
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• pp.145-152
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• 2018

This study is focused on manganese (Mn(II)) removal by ozonation in surface water. Instant ozone demand for the water was 0.5 mg/L in the study. When 0.5 mg/L of Mn(II) is existed in water, the optimum ozone concentration was 1.25 mg/L with reaction time 10 minutes to meet the drinking water regulation. The ozone concentration to meet the drinking water regulation was much higher than the stoichiometric concentration. The reaction of soluble manganese removal was so fast that the reaction time does not affect the removal dramatically. When Mn(II) is existed with Fe, the removal of Mn(II) was not affected by Fe ion. However As(V) is existed as co-ion the removal of Mn(II) was decreased by 10%. Adding ozone to surface water has limited effect to remove dissolved organic matter. When ozone is used as oxidant to remove Mn(II) in the water, the existing co-ion should be evaluated to determine optimum concentration.

• Journal of Environmental Science International
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• v.11 no.12
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• pp.1267-1274
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• 2002

This study was carried out to evaluate the pollutant removal efficiencies of the advanced drinking water treatment using ozonation process. For raw water, Nakdong River was used. By conducting batch test of ozonation, the following results were obtained. When ozone dosage of $5 mg/{\ell}$ was used, ozone transfer and utilization efficiencies of the ozonation were 94 to 92%, respectively. Removal efficiencies of single VOC compound or mixed VOC compounds in the raw water were 80% to 90% by the ozonation with $2 mg/{\ell}$ dosage and 10 minutes contact time. Removal efficiencies of ABS by the ozonation with $1 mg/{\ell}$, $3 mg/{\ell}$ dosage and 20 minutes contact time were 83% to 96%, respectively. Almost 67% of chlorophyll-a at the concentration of $38.4\mu\textrm{g}/{\ell}$ was removed by ozonation at ozone dosage of $1 mg/{\ell}$ for 20 min. Considering the efficiency of ozone utilization and water treatment, the most effective ozonation could be obtained with high ozone dosage and short contact time.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.6
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• pp.633-640
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• 2008

In this research, the $3.6m^3/day$ scale pilot plant consisting preozonation, coagulation, flocculation, and ceramic membrane processes was operated for long term period to evaluate the validity of ceramic membrane filtration process for treating lake water containing high concentration manganese. The higher concentration of dissolved manganese($Mn^{2+}$) was effectively oxidized to the bigger insoluble colloidal manganese ($MnO^2$) by 1~2 mg/L ozone. The colloidal manganese reacted with coagulant (poly aluminium chloride, PAC) and then formed the big floc. Ceramic membrane rejected effectively manganese floc during membrane filtration. Dissolved organic carbon(DOC) removal was dependent upon $Mn^{2+}$ concentration. While average $Mn^{2+}$ concentration was 0.43 and 0.85 mg/L in raw water, DOC removal rate in preozonation was 26.5 and 13.5%, respectively. The decrease rate of membrane permeability was faster without preozonation than with preozonation while membrane fouling decreased with NOM oxidation by ozone. In conclusion, raw water containing high concentration of manganese can be effectively treated in preozonation-coagulation-ceramic membrane filtration system.

• 연구논문집
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• s.33
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• pp.99-109
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• 2003

Recently the utilization of the ozone dissolved de-ionized water(DIW-$O_3$) in semiconductor wet cleaning process and photoresist stripping process to replace the conventional sulfuric acid and hydro peroxide mixture(SPM) method has been studied. In this paper, we propose the water-electrode type ozone generator which has the characteristics of the high concentration and purity to produce the high concentration DIW-$O_3$ for the photoresist strip process in the semiconductor fabrication. The proposed ozone generator has the dual dielectric tube structure of silent discharge type and the water is both used to electrode and cooling water. Through this study, we obtained the results of the 10.3 wt% of ozone gas concentration at the oxygen gas of 0.5 [liter/min.] and the DIW-$O_3$ concentration of 79.5 ppm.. Through the photoresist stripping test using the produced DIW-$O_3$, we confirmed that the photoresist coated on the silicon wafer was removed effectively in the 12 minutes.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.278-280
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• 2006

A hybrid discharge type ozonizer, which is superposed silent and surface discharges, has been designed and manufactured to apply for Nitrogen Oxides(NO) gas removal. The ozonizer consists of three electrodes, and is classified three types of ozonizer by changing applied voltage. Investigation was carried out variance with the flow rate of supplied oxygen gas, discharge power and the sorts of superposed discharge type ozonizer. Moreover, $NO(1200[ppm])/N_2$ gas removal investigation was also conducted to apply for environment improvement field. Two kinds of NO gas removal investigations were conducted. It distinguishes the investigations into NO gas reaction method. According to these studies, maximum removal rate of 100[%] in NO gas was obtained, and 8334[ppm] and 3249[mg/h] of maximum ozone concentration and generation were also obtained respectively.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1371-1380
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• 2007

Study on the instability of waste plastic's thermal pyrolysis oil was carried out for the purpose of improving its quality. The reaction of pyrolysis oil with ozone changed double bonds into aldehydes and ketone, estimated that HDPE pyrolysis oil contained $\sim45$ wt% 1-alkene type olefins, and PP pyrolysis oil did $\sim73$ wt% olefins, which consisted of $\sim47$ wt% secondary and $\sim20$ wt% primary alkenes. The dark brown color and odor of pyrolysis oil were improved by eliminating double bonds, indicated that they were directly related to unsaturated hydrocarbons. Container test showed that metal can affected oil quality worse than the brown glass bottle. Antioxidant added into pyrolysis oil was consumed up to 90% within $2\sim3$ days and the wt. composition of unsaturated hydrocarbons in pyrolysis oil was not changed within 50 days, inferring that instability of pyrolysis oil due to unsaturated bonds can be stabilized by antioxidants. Adsorption test on silica gel, activated carbon and alumina to remove precipitates in oil produced a good result, but not enough to remove moisture. However, cheap anhydrous sodium carbonate showed the best removal efficiency of moisture as well as precipitates in oil. Therefore the pyrolysis oil quality improvement was accomplished by applying anhydrous $Na_2CO_3$ into the production plant.