Hyen-Mi Chung

Different Inactivation Behaviors of MS-2 Phage and Escherichia coli in TiO2 Photocatalytic Disinfection

ABSTRACT Despite a wealth of experimental evidence concerning the efficacy of the biocidal action associated with the TiO2 photocatalytic reaction, our understanding of the photochemical mechanism of this particular biocidal action remains largely unclear. It is generally accepted that the hydroxyl radical (·OH), which is generated on the surface of UV-illuminated TiO2, plays the main role. However, our understanding of the exact mode of action of the hydroxyl radical in killing microorganisms is far from complete, and some studies report that other reactive oxygen species (ROS) (H2O2 and O2·−, etc.) also play significant roles. In particular, whether hydroxyl radicals remain bound to the surface or diffuse into the solution bulk is under active debate. In order to examine the exact mode of action of ROS in inactivating the microorganism, we tested and compared the levels of photocatalytic inactivation of MS-2 phage and Escherichia coli as representative species of viruses and bacteria, respectively. To compare photocatalytic microbial inactivation with the photocatalytic chemical degradation reaction, para-chlorobenzoic acid, which rapidly reacts with a hydroxyl radical with a diffusion-limited rate, was used as a probe compound. Two different hydroxyl radical scavengers, tert-butanol and methanol, and an activator of the bulk phase hydroxyl radical generation, Fe2+, were used to investigate their effects on the photocatalytic mode of action of the hydroxyl radical in inactivating the microorganism. The results show that the biocidal modes of action of ROS are very different depending on the specific microorganism involved, although the reason for this is not clear. It seems that MS-2 phage is inactivated mainly by the free hydroxyl radical in the solution bulk but that E. coli is inactivated by both the free and the surface-bound hydroxyl radicals. E. coli might also be inactivated by other ROS, such as O2·− and H2O2, according to the present results.

Disinfection of Water Containing Natural Organic Matter by Using Ozone-Initiated Radical Reactions

ABSTRACT Ozone is widely used to disinfect drinking water and wastewater due to its strong biocidal oxidizing properties. Recently, it was reported that hydroxyl radicals (·OH), resulting from ozone decomposition, play a significant role in microbial inactivation when Bacillus subtilis endospores were used as the test microorganisms in pH controlled distilled water. However, it is not yet known how natural organic matter (NOM), which is ubiquitous in sources of drinking water, affects this process of disinfection by ozone-initiated radical reactions. Two types of water matrix were considered for this study. One is water containing humic acid, which is commercially available. The other is water from the Han River. This study reported that hydroxyl radicals, initiated by the ozone chain reaction, were significantly effective at B. subtilis endospore inactivation in water containing NOM, as well as in pH-controlled distilled water. The type of NOM and the pH have a considerable effect on the percentage of disinfection by hydroxyl radicals, which ranged from 20 to 50%. In addition, the theoretical C̅T value of hydroxyl radicals for 2-log B. subtilis removal was estimated to be about 2.4 × 104 times smaller than that of ozone, assuming that there is no synergistic activity between ozone and hydroxyl radicals.

Inactivation of Escherichia coli by Photochemical Reaction of Ferrioxalate at Slightly Acidic and Near-Neutral pHs

ABSTRACT Fenton chemistry, which is known to play an effective role in degrading toxic chemicals, is difficult to apply to disinfection in water treatment, since its reaction is effective only at the acidic pH of 3. The presence of oxalate ions and UV-visible light, which is known as a photoferrioxalate system, allows the Fe(III) to be dissolved at slightly acidic and near-neutral pHs and maintains the catalytic reaction of iron. This study indicates that the main oxidizing species in the photoferrioxalate system responsible for microorganism inactivation is OH radical. Escherichia coli was used as an indicator microorganism. The CT value (OH radical concentration × contact time; used to indicate the effect of the combination of the concentration of the disinfectant and the contact time on inactivation) for a 2-log inactivation of E. coli was approximately 1.5 × 10−5 mg/liter/min, which is approximately 2,700 times lower than that of ozone as estimated by the delayed Chick-Watson model. Since the light emitted by the black light blue lamp is similar to sunlight in the specific wavelength range of 300 to 420 nm, the photoferrioxalate system, which can have a dual function, treating water for both organic pollutants and microorganisms simultaneously, shows promise for the treatment of water or wastewater in remote or rural sites. However, the photoferrioxalate disinfection system is slower in inactivating microorganisms than conventional disinfectants are.

Effect of pH and Importance of Ozone initiated Radical Reactions In Inactivating Bacillus subtilis Spore

Abstract The effect of pH on the inactivation of Bacillus subtilis spores with ozone in a batch reactor was examined in association with the role of OH radicals. The exact effect OH radicals have on ozone inactivation of microorganism is not well understood, although a direct reaction of molecular ozone has sometimes been emphasized. This study reports a novel observation that the presence of OH radicals plays a significant role in microbial inactivation. Considering the dependence of the ozone decay rate on pH, the observed C¯ T values for achieving a 2 log inactivation using the modified Chick-Watson model was 40 % lower at pH 8.2 compared to that at pH 5.6. In the presence of OH radical scavengers (tert-butanol), the observed change of C¯ T with pH was within 10%. This difference could be explained by the significant role of OH radicals.

Pathogens in water deer (Hydropotes inermis) in South Korea, 2010-12.

Abstract Water deer (Hydropotes inermis) are among the most common wildlife to approach farmhouses and livestock barns in Korea. We collected 305 water deer from Gangwon (n = 168), South Chungcheong (n = 89), and Gyeongsang (n = 48) provinces in 2010–12 and used PCR and serologic tests to screen the deer for pathogens. In 2010, tests for bovine viral diarrhea virus (BVDV), rotavirus, and Brucella abortus were positive in 8% (5/60), 2% (1/60), and 59% (33/56) of the animals, respectively. In 2010, the water deer were negative for foot-and-mouth disease virus, coronaviruses, and Mycobacterium bovis. All samples collected in 2011 and 2012 were negative for all pathogens analyzed. These results suggest that at least two of the investigated pathogens, BVDV and B. abortus, circulate among water deer in South Korea.

Prevalence of avian influenza virus in wild birds before and after the HPAI H5N8 outbreak in 2014 in South Korea.

Since 2003, highly pathogenic avian influenza (HPAI) virus outbreaks have occurred five times in Korea, with four HPAI H5N1 outbreaks and one HPAI H5N8 outbreak. Migratory birds have been suggested to be the first source of HPAI in Korea. Here, we surveyed migratory wild birds for the presence of AI and compared regional AI prevalence in wild birds from September 2012 to April 2014 for birds having migratory pathways in South Korea. Finally, we investigated the prevalence of AI in migratory birds before and after HPAI H5N8 outbreaks. Overall, we captured 1617 migratory wild birds, while 18,817 feces samples and 74 dead birds were collected from major wild bird habitats. A total of 21 HPAI viruses were isolated from dead birds, and 86 low pathogenic AI (LPAI) viruses were isolated from captured birds and from feces samples. Spatiotemporal distribution analysis revealed that AI viruses were spread southward until December, but tended to shift north after January, consistent with the movement of migratory birds in South Korea. Furthermore, we found that LPAI virus prevalences within wild birds were notably higher in 2013–2014 than the previous prevalence during the northward migration season. The data from our study demonstrate the importance of the surveillance of AI in wild birds. Future studies including in-depth genetic analysis in combination with evaluation of the movement and ecology of migratory birds might help us to bridge the gaps in our knowledge and better explain, predict, and ultimately prevent future HPAI outbreaks.

Tracking Mallards (Anas platyrhynchos) with GPS Satellite Transmitters Along Their Migration Route Through Northeast Asia.

SUMMARY. In this study, Global Positioning System satellite transmitters were attached to three mallards (Anas platyrhynchos) wintering in South Korea to track their migration routes, stopover sites, breeding sites, and migration patterns. We successfully tracked only one mallard (no. 108917) from November 15, 2011, to November 29, 2013, and determined separate migration routes in two cases of spring migration and one case of fall migration. The mallard repeatedly migrated to the same final destination, even though the travel path varied. We identified six stopover sites: Hunhe River, Liaohe River, Yinma River, Yalu River, Songjeon Bay, and Dahuofang Reservoir in China and South Korea. The wintering sites of two migration cases were discovered to be identical (Gokgyo River in Asan, South Korea). The terminal sites, which were presumed to be breeding grounds, were the same in both cases (Hinggan League in Inner Mongolia Autonomous Region, China). On the basis of the migration routes identified in this study, we suggest that future efforts to control highly pathogenic avian influenza (HPAI) should not only include avian influenza surveillance but also implement flyway-based strategies, with regard to all countries affected by potential HPAI outbreaks.

A mini-review on discharge characteristics and management of microplastics in sewage treatment plants

As the issue of microplastics (MPs) detection in tap water was raised in other countries in 2017, monitoring of MPs in drinking and source water, and sewage treatment plant (STP) effluents was initiated. This study intends to look into other studies on MPs in STPs at home and abroad, and review the characteristics of MPs and their removal efficiencies in the STPs, the risk and effect of MPs on watersheds, and management practices in order to help better understand MPs in STPs. To manage MPs effectively in STPs, it is necessary to investigate the detection of MPs discharged from STPs, do research on human health risk and control measures, and build a monitoring system including standardized analytical methods.

Residual Multi Pesticides Screening of Dead Birds by Orbitrap High Resolution Mass Spectrometry

BACKGROUND: The objective of this study was to evaluate screening method of residual multi pesticides in dead birds by Orbitrap high resolution mass spectrometry (HRMS) to identify the cause of death for birds . METHODS AND RESULTS: Extraction and clean-up methodof residual pesticides in liver of deadbirdswas used QuEChERS (Quick Easy Cheap Effective Rugged and Safe) and method validations was conducted using liquid chromatography and gas chroamtography with triplequadrupole mass spectrometer (LC/MS/MS and GC/MS/ MS) Also, we were evaluated screening method for the determination of residual pesticides in liver of dead birds by LCandGCOrbitrapMass Spectrometry. Results ofmethod validations, Correlation coefficients of the matrix matched calibration curves were >0.978, and the method detection limits (MDLs) and limits of quantitation (LOQ) were 2.8~ 72.1 ng/g (18.4 ng/g on average) and 9.0~230 ng/g (58.5 ng/g on average). The accuracy ranged from69.1%to130% (103%on average), and the precision values were less than 14.8%(3.8%onaverage). Thescreeningof residual pesticides in liver of dead birds by LC and GC Orbitrap HRMS was detectedmonocrotophos, carbofuran, carbosulfan, deltametrin, benfuracarb, carbofuran, phosphamidon, prochloraz in investigated samples. CONCLUSION: This results showed that accurate mass were extraction of residual pesticides in dead birds by Orbitrap HRMS. It suggested that this screeningmethod is applicable to the residual pesticide analysis for the cause of death as a main tool.

Nocardioides suum sp. nov. isolated from the air environment in an indoor pig farm

A bacterial strain PBT33-2T was isolated from the air environment in an indoor pig farm. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain PBT33-2T belonged to the genus Nocardioides in the phylum Actinobacteria, and was most closely related to Nocardioides daphnia D287T in a maximum-likelihood and neighbor-joining phylogenetic trees. Strain PBT33-2T shared 95.3% sequence identity with N. daphnia D287T. However, the highest sequence similarity was shown with N. sediminis MSL-01T (96.0%). It had less than 96.0% sequence identities with other type species of the genus Nocardioides. Strain PBT-33-2T grew at 15–45°C (optimum 20–35°C), pH 5.0–11.0 (optimum pH 7.0) and 0–4.0% (w/v) NaCl (optimum 0%). The major fatty acid and quinone were iso-C16:0 and MK-8, and the DNA G+C content of strain PBT33-2T was 69.3 mol%. On the basis of poly-phasic results, strain PBT33-2T represents a novel species of the genus Nocardioides, for which the name Nocardioides suum sp. nov. is proposed. Its type strain is PBT33-2T (=KCTC 39558T =DSM 102833T).