• 수도
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• v.24 no.6 s.87
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• pp.23-31
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• 1997

Ozonation is an effective process in providing microbiologically safe drinking water. The operation of the ozonation stage is often based on disinfection criteria which include security factors, such as the CT criterion. This type of ozonation management, which mat include large safety margins, will no longer be possible, since formation of ozonation byproducts has to be avoided. In order to reduce the security factor, a computerized tool to predict with more accuracy inactivation of micro-organisms in the ozonation process has been developed.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.755-761
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• 2006

Recently, there is growing interest in ultraviolet (UV) irradiation as a disinfection technic in drinking water production due to its effectiveness to inactivate microorganisms such as Crytosporidium parvum without forming disinfection byproducts. However, UV disinfection is known for its drawback such as photoreactivation. Despite many works concerning the photoreactivation, most of works were focused on indicator or non pathogenic microorganisms. The objective of this study is to examine the photoreactivation of Pseudomonas aeruginosa which is an opportunistic pathogen as UV radiation by LP and MP UV lamp was applied. The result showed that P. aeruginosa had high photo repair efficiency regardless of the type of UV irradiation. Both of the effective log repair values of LP and MP UV irradiation were found approximately 2.6 log. In addition, photo repaired P. aeruginosa was not significantly different in forming biofilm in comparison with non treated P. aeruginosa.

• The KSFM Journal of Fluid Machinery
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• v.20 no.2
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• pp.69-74
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• 2017

Sodium hypochlorite, used as water disinfectant, is generated by electrolysis of salt. Compared to chlorine gas disinfection, it is free from high-pressure gas regulation and does not generate toxic gas, so it is increasingly used as a safe disinfectant. Despite these advantages, the concentration of sodium hypochlorite decreases with temperature during long-term storage, and the amount of chlorate increases when a large amount is added, it has mainly been applied to small-scale waterworks. To solve this problem, high sodium hypochlorite generation was developed. In this study, the changes of concentration and chlorate of sodium hypochlorite with time has been studied. As a result of the test, it was found that the usable period of sodium hypochlorite produced at a certain temperature or less was increased from 1.5 days to 13 days. Overall, sodium hypochlorite can be applied even in large-scale waterworks, which makes operation more stable and also reduces the disinfection byproducts, thus it contributed greatly to securing water quality.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.9
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• pp.1-5
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• 2009

Disinfection using UV irradiation has been considered to an alternative for chlorination because it does not suffer from disinfection byproducts problem. The aim of this study was to verify if UV irradiation with 368.6[nm] wavelength has a potential to be used a efficient disinfection. UV irradiation was given for 60 minutes to E. coli. which was used as a model microorganism. Remarkable decrease in number of microorganism was not observed for initial 30 minutes, however, 83.3[%] of disinfection efficiency was achieved after 30 minutes of irradiation. Inactivation constant, k was determined to 0.00868[$cm^2$]/([$mW{\cdot}s$]) using kinetic approach.

• Journal of Korean Society on Water Environment
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• v.28 no.5
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• pp.754-761
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• 2012

Several drinking water treatment plants (DWTPs) produce the bottled tap waters (BTWs) as pilot production and provide them for noncommercial use. In 2008, acetaldehyde and chloral hydrate were detected in some BTWs and the public worry over the safety of the water. In this study, the BTWs produced from 7 DWTPs were tested for 13 chemicals including disinfection byproducts (DBPs). The level of four trihalomethanes (THMs) were increased up to 15 days. The average concentration of them was 0.0075 mg/L at the time of bottling and it was increased to 0.0214 mg/L after 15 days. The average acetaldehyde concentration was 0.0406 mg/L at the time of bottling but it was went up to 0.2251 mg/L after 11 days and then decreased. Although the initial concentrations of DBPs were below the drinking water standard, we also traced them at different storage conditions. Temperature affected the formations of THMs and acetaldehyde concentrations significantly. While the average concentration of THMs ranged from 0.0113 to 0.0182 mg/L at $25^{\circ}C$, it was increased to 0.0132 ~ 0.0256 mg/L at $50^{\circ}C$. In case of acetaldehyde, concentration ranged from 0.0901 to 0.2251 mg/L at $25^{\circ}C$, it was increased to 0.3394 ~ 1.0591 mg/L at $50^{\circ}C$. Throughout the tests with 7 BTWs samples, none of the chemicals was exceeded the drinking water standard of Korea. Therefore, it is recommended to avoid the exposure of BTWs to sunlight or high temperature during distribution and storage.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.2
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• pp.224-227
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• 2005

먹는물에서 염소소독 부산물로서 휘발성유기화합물인 디클로로아세트니트닐(DCAN), 트리클로로아세트니트릴(TCAN), 디브로모아세트니트릴(DBAN), 브로모클로로아세트니트릴(BCAN)의 4종류의 물질을 대상으로 탈기법(air stripping) 및 탈기법(air stripping)과 자외선에너지($8\;W{\times}6$)를 이용하여 분해시험을 행하였다. 물질들의 확인은 가스크로마토 그래프, 이온크로마토그래프 그리고 자외선분광광도계를 사용하였다. TCAN은 탈기법 이용한 방법에서 제거가 되었으며, DBAN과 BCAN에서는 자외선에너지에 의해 분해가 되었다.

• Analytical Science and Technology
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• v.16 no.3
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• pp.249-260
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• 2003

The disinfection of drinking water to control microbial contaminants results in the formation of secondary chemical contaminants, DBPs (disinfection by-products). It was studied the formation pattern of DBPs in drinking raw water after hypochlorite, chlorine disinfectant, was added in this study. It was determined TOC (total organic carbon), residual chlorine, turbidity and DBPs in raw water from Han-river during 1~14 days. Total DBPs was $101.3ng/m{\ell}$ (789.6 nM) after 7days and THMs (trihalomethanes) are the dominant portion of 69%. HAAs (haloacetic acids) and chloral hydrate were determined 19% and 10% respectively, and HANs (haloacetonitriles), HKs (haloketones) and chloropicrin were analyzed in trace level. Chloroform occupied about 89% in total THMs in concentration of $61.5ng/m{\ell}$, 95% of HANs was DCAN (dichloroacetonitrile) in $0.72ng/m{\ell}$, 50% of HAAs was TCAA (trichloroacetic acid). On the study of relationship in formation among the DBPs, HANs forms with THMs competitively to the point of the concentration of $40ng/m{\ell}$ of THMs. For HAAs, it did not show the prominent tendency. But it was observed that the compounds of large oxidation state are formed at first, and becomes to the compounds of low oxidation states.

• 한국균학회소식:학술대회논문집
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• 2014.10a
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• pp.25-25
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• 2014

Three species of Fusarium, F. fujikuroi, F. verticillioides and F. proliferatum, are known to be associated with bakanae disease of rice [1, 2]. F. fujikuroi infects rice flowers and survive in endosperm and embryo of the seeds. Infected seed is an important source of primary inoculum of pathogens [3]. Seeds of rice (Oryza sativa cv. Boramchan) collected from bakanae-infected field were found to be 96% infected with Fusarium sp., 52% with F. fujikuroi, 42% with F. verticillioides, and 12% with F. proliferatum as determined by incubation method and species-specific PCR assays. F. fujikuroi was detected at lemma/palea, endosperm and embryo whereas F. verticillioides and F. proliferatum were recovered only from lemma/palea by means of component plating test. Seed disinfection methods have been developed to control bakanae disease and prochloraz has been most widely used for rice seeds. Two chemicals formulated with prochloraz (PC 1) and prochloraz + hexaconazole (PC 2) that inhibit biosynthesis of ergosterol strongly reduced the incidence of Fusarium spp. on selective media to 4.7% and 2.0%, respectively. Disease symptoms of rice seedlings in nursery soil were alleviated by chemical treatment; seedlings with elongated leaves or wide angle between leaf and stem were strikingly reduced from 15.6 to 3.2% (PC 1) and 0 (PC 2), stem rots were reduced from 56.9 to 26.2% (PC 1) and 32.1% (PC 2), and normal seedling increased from 0.4 to 13.3% (PC 2). Prochloraz has some disadvantages and risks such as the occurrence of tolerant pathogens [4] and effects on the sterol synthesis in animals and humans [5]. For these reasons, it is necessary to develop new disinfection method that do not induce fungal tolerance and are safe to humans and animals. Chlorine dioxide ($ClO_2$), that is less toxic, produces no harmful byproducts, and has high oxidizing power, has been reported to be effective at disinfection of several phytopathogenic fungi including Colletotrichum spp. and Alternaria spp. [6]. Gaseous $ClO_2$ applied to rice seeds at a concentration of 20 ppm strongly suppressed mycelial growth of Fusarium fujikuroi, F. verticillioides and F. proliferatum. The incidence of Fusarium spp. in dry seed with 8.7% seed moisture content (SMC) tended to decrease as the concentration of $ClO_2$ increased from 20 to 40 ppm. Applying 40 ppm $ClO_2$ at 90% relative humidity, incidence was reduced to 5.3% and resulted in significant reduction of disease symptoms on MS media. In nursery soil, stem rot was reduced from 56.9 to 15.4% and the number of normal seedlings increased from 0.4 to 25.5%. With water-soaked seeds (33.1% SMC) holding moisture in the endosperm and embryo, the effectiveness of disinfection using $ClO_2$ increased, even when treated with only 20 ppm for four hours. This suggests that moisture was a key element for action of $ClO_2$. Removal of the palea and lemma from seeds significantly decreased the incidence of Fusarium spp. to 3.0%. Seed germination appeared to decrease slightly by water-soaking at $30^{\circ}C$ because of increased SMC and by physical damage of embryos from hulling. These results indicate that the use of gaseous $ClO_2$ was effective as a means to disinfect rice seeds infected with Fusarium spp. and that moisture around the pathogens in the seed was an important factor for the action of $ClO_2$. Further investigations should be conducted to ascertain the best conditions for complete disinfection of Fusarium spp. that infect deep site of rice seeds.

• Environmental Engineering Research
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• v.12 no.5
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• pp.224-230
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• 2007

The objectives of this study were to evaluate the change of molecular weight (MW) profiles in natural organic matter (NOM) through various treatment processes (coagulation, granular activated carbon (GAC), and ozonation) using high performance size exclusion chromatography based on ultraviolet absorbance and dissolved organic detection (HPSEC-UVA-DOC). In addition, relationships between MW profiles and disinfection by-production (DBP) formation were evaluated. Each treatment process results in significant different effects on NOM profiles. Coagulation is effective to remove high molecular weight NOM, while GAC is effective to remove low molecular weight NOM. Ozonation removes only a small portion of NOM, while it induces a significant reduction of UV absorbance due to breakdown of the aromatic groups. All treated waters are chlorinated, and chlorination DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) are measured under formation potential conditions. Both THM and HAA formation potentials were significantly reduced through the coagulation process. GAC was more effective to reduce THM formation compared to HAA formation reduction, while ozonation showed significant HAA reduction compared to THM reduction.

• Journal of environmental and Sanitary engineering
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• v.22 no.4
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• pp.23-32
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• 2007

Changes in the characteristics of dissolved organic matter was studied at selected stations in the Nakdong river basin using physical and chemical methods. Characteristics of dissolved organic matters were analysed and assessed. Production of disinfection byproducts were also investigated. Distribution of the organic compounds according to the Molecular weight(MW) indicate that MWs higher than 100K were highest with cattle excrement wastewater and MW between 100-10K were highest with waters from forest streams. Low MW compounds (Jess than 1K) were highest with the effluents from environmental facilities. Results of resin fractionation study show that acidic hydrophobic substances(AHS) were dominant in many stations. The values were higher in the samples from mainstreams and sidestreams where the influence of organic matter is higher than the water from environmental facilities. Hydrophilic neutral substances(HoN) such as hydrocarbon, pesticides and detergents were higher in the wastewater treatment facilities. HoN values of water from the forest streams were 4.7% indicating there is no synthetic pollutant.