• Journal of Korean Society of Environmental Engineers
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• v.29 no.5
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• pp.533-539
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• 2007

Cell culture infectivity assay using HCT-8 cell was combined with most-probable-number technique to evaluate the inactivation of Cryptosporidium parvum by various disinfectants, including chlorine, ozone, and UV light. The assay was demonstrated to be as sensitive as animal infectivity assay, which has been considered the "gold standard" for assessing Cryptosporidium oocyst infectivity, and a valuable tool to evaluate inactivation of C. parvum by disinfectants. Bench-scale inactivation study showed that at the condition of $5^{\circ}C$ and pH 7.0, CT value of $1,250mg{\cdot}min/L$ by chlorine and $16mg{\cdot}min/L$ by ozone were required to achieve approximately 1.0 log inactivation of C. parvum, suggesting that even ozone could not be sufficient to inactivate C, parvum at low. temperature. Unlike chlorine and ozone, UV light is very effective to inactivate C. parvum, regardless of temperature. A UV light dose of 2 $mJ/cm^2$ provided at least 3 log inactivation of C. parvum.

• Journal of the Korean Ceramic Society
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• v.39 no.9
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• pp.840-845
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• 2002

As an ozone gas sensor, the semiconductor gas sensor which is cheap, portable and simple in use and has a high sensitivity and an excellent selectivity, has been known as an alternative. In the present study, ITO ($In_2O_3 95%,\;SnO_2$ 5%) thin films were deposited on the alumina substrate by using R.F. magnetron sputtering method. The substrate temperature was 300$^{\circ}C$ and 500$^{\circ}C$, respectively and then some specimens were annealed at 500$^{\circ}C$ for 4h in air. ITO gas-sensing films formed crystallines before and after annealing. As results of gas sensitivity measurements to an ozone gas, the sensor deposited at 300$^{\circ}C$ and then annealed has the highest sensitivity (sensible below 1 ppm). As the operating temperature increased gradually, the sensitivity decreased but the response time and stability improved.

• Analytical Science and Technology
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• v.35 no.5
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• pp.212-217
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• 2022

In this study, ozone (O₃) samples were prepared for investigating the heterogeneous reactions between O₃ and tropospheric aerosols and were characterized by spectroscopic methods. O₃ generated from an ozone generator was purified by selective adsorption on refrigerated silica gel, followed by transfer to a sample bulb. The amount of UV light (λ = 256 nm) absorbed by O₃ was measured as a function of time at two different temperatures (room temperature and 50 ℃) and under different irradiation conditions. A correlation plot of 1/[O₃] versus time showed that O₃ decomposition follows the 2^nd order reaction rate under a steady-state approximation. The initial concentration of O₃, observed rate constants (k_obs), and the half-life of O₃ in the sample stored at room temperature were determined to be 2.74 [±0.14] × 10¹⁶ molecules·cm^-3, 4.47 [±0.64] × 10^-23 molecules^-1·cm³·s^-1, and 9.5 [±1.4] days, respectively. The evaluation of O₃ stability under various conditions indicated that special care should be taken to prevent the exposure of the O₃ samples to hightemperature environment and/or UV radiation. This study established a protocol for the preparation of highly purified O₃ samples and confirmed that the O₃ samples can be stored for a day after preparation for further experiments.

• Transactions on Electrical and Electronic Materials
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• v.2 no.1
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• pp.12-15
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• 2001

Bi-2212 and Bi-2223 thin films are prepared by IBS(ion beam sputtering) technique. Three phases of Bi-2201, Bi-2212 and Bi-2223 appear as stable ones in spite of the conditions for thin film fabrication of Bi-2212 and Bi-2223 compositions, depending on substrate temperature (T $_{sub}$) and ozone pressure(PO$_3$). It is found out that these phases are limited within very narrow temperature.e.

• Journal of the Korean Professional Engineers Association
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• v.34 no.2
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• pp.23-27
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• 2001

Until 1996, CFC refrigerants haven't been used because it destroyed ozone that affecting In ecosystem. And HCFC will prohibit until 2020. In Europe, they attempt to move up its fulfillment. Until now the change have completed CFC into HFC134a and is considerated HCFC into HFC410A and HFC407C. But HFC41 OA has high condenser temperature and HFC407C is non-azeotropic refrigerant mixture and gliding temperature phenomenon. New refrigerant ell POE, PVE, PAG was also developed.

• Journal of the Korean Professional Engineers Association
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• v.15 no.2
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• pp.24-31
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• 1982

This study concerns with the reduction of the COD and deceleration of dyeing wastewater from DAEGU city area by ozonation. The COD reduction by ozonation follows near linear relationships versus ozonation time, temperature and concentration. The color in dyeing wastewater and of dyes can he strikingly reduced as the water is quasi colorless after ozone treatment. COD reduction rate of wastewater was found not to be dependented on pH, however, high temperature gave better results, although economically not feasible. The ozonation of dyeing wastewater can give good results when dyes, scouring agent and sticking agents were pre-separated.

• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.1082-1087
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• 2006

BAC backwashing process in ozone-BAC advanced water treatment process was experimentally studied. The operation and performance of backwashing were evaluated by measuring the effects of water temperature and water input rate on the backwashing interval and duration, and also the change of the amounts of biofilm and HPC in treated water before and after backwashing. The experiments were carried out with the pilot scale test module built in a existing water treatment plant, and the following results were obtained. Longer backwashing time than that of design operating condition was needed for satisfying the suitable turbidity of washing water effluent. Depending on water temperature, 7 days of backwashing cycle was recommended for the period lower than $15^{\circ}C$, and 10 days for the period higher than $15^{\circ}C$. After backwashing, the amounts of biofilm and HPC decreased to 1/10 and 80%, respectively.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.83-90
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• 2006

Performance and operation of BAC in ozone-BAC advanced water treatment process were investigated using the pilot scale test plant built in D water purification plant. The performance was evaluated by the removal efficiencies of DOC, BDOC, ammonia nitrogen and THMs. The effect of EBCT on DOC removal was experimented for an effective operating condition, and the amount of attached biofilm was analyzed in various water temperatures and position of BAC. Two removal mechanisms, adsorption and biological decomposition by attached biofilm, were predominant to decrease the concentration of various contaminants. DOC was removed 40%, and the removal rate was decreased in winter time due to the lowered activity of attached biofilm. BDOC was effectively removed. THMs and ammonia nitrogen were mainly removed not in ozonation process but in BAC. Water temperature deeply influenced in removal efficiency of ammonia nitrogen. The amount of attached biofilm depended on water temperature and height of packed activated carbon column. Considering DOC removal efficiency and design EBCT of commercial BAC plant, the proper EBCT was 12.5 minutes.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1705-1707
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• 1998

In this paper, a superposed discharge type ozonizer was designed and manufactured. The ozonizer is equipped with three electrodes : central electrode, internal electrode and external electrode, and it consists of two gaps. The ozone is generated by superposing silent discharge, which are respectively generated betweens two gaps. This paper describes the following two characteristics : (1) 'the characteristics of discharge with variation with output voltage of AC High Voltage source, quantity of the supplied gas and discharge voltage (2) the characteristics of ozone discharge power, temperature of the supplied gas.

• Journal of Korean Society for Atmospheric Environment
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• v.11 no.E
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• pp.31-43
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• 1995

Natural emissions of NOx from soils were measured at an agricultural corn field during 3 weeks of growing season in summer (from May to June) 1995. This experiment was conducted in an effort to characterize the role of soil NOx on tropospheric ozone formation in rural atmosphere, and understand the natural NOx emission mechanism with respect to soil parameters. NO fluxes were ranged from 3.1 ng Nm$^{-2}s^{-1}$ to 259.0 ng Nm$^{-2}s^{-1}$, and average NO flux during experimental period was found to be 47.6 $\pm$ 50.6 ng Nm$^{-2}s^{-1}$ with 732 number of data. Diurnal variation of NO flux was shown clearly with daytime maximum and nighttime minimum. NO fluxes were correlated with soil temperature. Exponential soil temperature dependency of NO fluxes was found with 0.0160$^{circ}C^{-1} of k and r^2=0.508$, which agrees well to the value estimated at corn fields in eastern United States. The significant increases of NO fluxes from agricultural soil were detected after applying N fertilizers to soil. THe mechanisms attributed to this are enhanced biological nitrification and denitrification. In the view of rural ozone formation, the roles of natural NO emissions are very essential, especially in NOx - limited region such as southern United States.