• Journal of Microbiology and Biotechnology
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• v.23 no.3
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• pp.382-389
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• 2013

Propionate is an important intermediate product during the methane fermentation of organic matter, and its degradation is crucial for maintaining the performance of an anaerobic digester. In order to understand the effect of temperature on propionate degradation, an upflow anaerobic sludge blanket (UASB) reactor with synthetic wastewater containing propionate as a sole carbon source was introduced. Under the hydraulic retention time (HRT) of 10 h and influent propionate of 2,000 mg/l condition, propionate removal was above 94% at 30-$35^{\circ}C$, whereas propionate conversion was inhibited when temperature was suddenly decreased stepwise from $30^{\circ}C$ to $25^{\circ}C$, to $20^{\circ}C$, and then to $18^{\circ}C$. After a long-term operation, the propionate removal at $25^{\circ}C$ resumed to the value at 30- $35^{\circ}C$, whereas that at $20^{\circ}C$ and $18^{\circ}C$ was still lower than the value at $35^{\circ}C$ by 8.1% and 20.7%, respectively. Microbial community composition analysis showed that Syntrophobacter and Pelotomaculum were the major propionate-oxidizing bacteria (POB), and most POB had not changed with temperature decrease in the UASB. However, two POB were enriched at $18^{\circ}C$, indicating they were low temperature tolerant. Methanosaeta and Methanospirillum were the dominant methanogens in this UASB and remained constant during temperature decrease. Although the POB and methanogenic composition hardly changed with temperature decrease, the specific $COD_{Pro}$ removal rate of anaerobic sludge (SCRR) was reduced by 21.4%-46.4% compared with the control ($35^{\circ}C$) in this system.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.6-12
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• 2014

In the present work, $WO_3$ and $WO_3-TiO_2$ were prepared by the chemical deposition method. Structural variations, surface state and elemental compositions were investigated for preparation of $WO_3-TiO_2$ sonocatalyst. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) were employed for characterization of these new photocatalysts. A rhodamine B (Rh.B) solution under ultrasonic irradiation was used to determine the catalytic activity. Excellent catalytic degradation of an Rh.B solution was observed using the $WO_3-TiO_2$ composites under ultrasonic irradiation. Sonocatalytic degradation is a novel technology of treating wastewater. During the ultrasonic treatment of aqueous solutions sonoluminescence, cavitaties and "hot spot" occurred, leading to the dissociation of water molecules. In case of a $WO_3$ coupled system, a semiconductor coupled with two components has a beneficial role in improving charge separation and enhancing $TiO_2$ response to ultrasonic radiations. In case of the addition of $WO_3$ as new matter, the excited electrons from the $WO_3$ particles are quickly transferred to $TiO_2$ particle, as the conduction band of $WO_3$ is 0.74 eV which is -0.5 eV more than that of $TiO_2$. This transfer of charge should enhance the oxidation of the adsorbed organic substrate. The result shows that the photocatalytic performance of $TiO_2$ nanoparticles was improved by loading $WO_3$.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.7
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• pp.729-734
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• 2008

The higher valence state of iron i.e., Fe(VI) was employed for the treatment of Cu(II)-EDTA in the aqueous/waste waters. The ferrate(VI) was prepared through wet oxidation of Fe(III) by sodium hypochlorite. The purity of prepared Fe(VI) was above 93%. The stability of Fe(VI) solution decreased as solution pH decreased through self decomposition. The reduction of Fe(VI) was obtained by using the UV-Visible measurements. The dissociation of Cu(II)-EDTA complex through oxidation of EDTA using Fe(VI) and subsequent treatment of organic matter and metal ions by Fe(III) reduced from Fe(VI) in bench-scale of continuous flow reactor were studied. The removal efficiencies of copper were 69% and 79% in pH control basin and reactor, respectively, at 120 minutes as retention time. In addition, Cu(II)-EDTA in the reactor was decomplexated more than 80% after 120 minutes as retention time. From this work, a continuous treatment process for the wastewater containing metal and EDTA by employing Fe(VI) as muluti-functional agent was developed.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.6
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• pp.442-448
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• 2013

There are two approaches in measuring colors (or chromaticity) in water, i.e., visual comparison method and spectrophotometric method. The color of sample was determined by comparing with that of platinum-cobalt standard solution in the visual comparison method. Single or multiple wavelengths are used for the spectrophotometric method. As the accuracy and precision of visual comparison method depend on the eye sight of the analyzer, the results are not so reliable and representative. In addition, it is hard to measure chromaticity less than 5 TCU. Single wavelength approach in spectrophotometric method, can be applied for groundwater or surface water with natural organic matter (i.e., humic substances) while it's hard to measure the color of wastewater which includes anthropogenic chemical compounds. The measurements with multiple wavelengths approach resulted in reliable data regardless of the source of sample water, i.e., surface water and wastewater. As dozens of measurements and complicated calculations for one sample were required for the multiple wavelengths approach, the approach could not be applied for field measurement. In the present study, the authors tested efficient method which could measure the color of water sample accurately and precisely regardless of the source of water. With the colorimeter with multiple wavelengths and calculation program, the colors of water samples could be measured within 3~4 seconds with accuracy and precision.

• Korean Journal of Environmental Agriculture
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• v.5 no.1
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• pp.11-23
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• 1986

Soils and rice plants in wastewater irrigated area of the Mangyeong River receiving waster from the Jeonju Industrial Complex and municipal sewage were sampled at two depths to assess the nature and content of Cd, Cu, Pb and Zn, particularly with respect to distance from wastewater source. For metal levels of soils in these area, no difference in the heavy metal contents between the surface and the subsurface soils was found. Total contents of Cu, Pb and Zn in soils were negatively correlated with distance from the source. A positive correlation was found between contents of total and 0.1N-HCl extractable or $1N-CH_3COONH_4$ extractable heavy metals in surface soils of these area. Total contents of heavy metals in soils were positively correlated with clay, soil organic matter and cation exchange capacity. Heavy metal contents of brown rice sampled at the Jeon-ju Industrial Complex area ranged from 0.15 to 0.91 ppm for Cd, from 1.13 to 5.68 ppm for Cu, from 0.22 to 7.16 ppm for Pb and from 11.74 to 38.66 ppm for Zn. Negative correlation was found between the contents of Cd, Cu, Pb, and Zn in the brown rice and the distance from the source. The contents of Cd, Cu and Zn in rice straw were positively correlated with those in the brown rice.

• Journal of Environmental Health Sciences
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• v.35 no.6
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• pp.517-525
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• 2009

The water quality of Lake Shihwa had been rapidly deteriorating since 1994 due to wastewater input from the watersheds, limited water circulation and the lack of a wastewater treatment policy. In 2000, the government decided to open the tidal embankment and make a comprehensive management plan to improve the water quality, especially inflowing stream water around Shihwa and Banwol industrial complex. However, the water quality and microbial community have not as yet been fully evaluated. The purpose of this study is to investigate the influent water quality around the industrial area based on chemical and biological analysis, and collected surface water sample from the Siheung Stream, up-stream to down-stream through the industrial complex, Samples were collected in July 2009. The results show that the downstream site near the industrial complex had higher concentrations of heavy metals (Cu, Mn, Fe, Mg, and Zn) and organic matter than upstream sites. A combination of DGGE (Denaturing Gradient Gel Electrophoresis) gels, lists of K-WQI (Korean Water Quality Index), cluster analysis, MDS (Multi-Dimensional Scaling) and PCA (Principal Component Analysis) has demonstrated clear clustering between Siheung stream 3 and 4 and with a high similarity and detected metal reducing bacteria (Shewanella spp.) and biodegrading bacteria (Acinetobacter spp.). These results suggest that use of both chemical and microbiological marker would be useful to fully evaluate the water quality.

• Journal of Wetlands Research
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• v.23 no.4
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• pp.372-380
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• 2021

Non-point source pollutants and high-concentration livestock wastewater are reported as major factor of water pollution in water system and wet-land. So, LID is suggested as a method to manage of them. wet-lands is presented as effective method for management of NPS from agriculture and livestock farm area based on various NPS reduction mechanism. In this research, the application of wet-lands was evaluated based on monitoring and modeling of agriculture and livestock farm in J city, Jeollabuk-do. As a resutl, EMC during rainfall event was found to be about 27 times higher than dry season based on a BOD. indicating that the management of non-point pollutants is urgent. Modeling-based wet-land reduction efficiency was BOD 57.5%, TN 48.9% and Tp 64.2%. However, removal efficiency of wet-land tends to decrease during the winter and large amounts of rainfall runoff occur, it is necessary to manage of wet-land. Based on the results of this research, wet-land could be proposed as an alternative to stable management of NPS in agriculture and livestock farm area.

• Korean Journal of Ecology and Environment
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• v.56 no.4
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• pp.281-302
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• 2023

Carbon is not only an essential element for life but also a key player in climate change. The radiocarbon (¹⁴C) analysis using accelerator mass spectrometry (AMS) is a powerful tool not only to understand the carbon cycle but also to track pollutants derived from fossil carbon, which have a distinct radiocarbon isotope ratio (Δ¹⁴C). Many studies have reported Δ¹⁴C of carbon compounds in streams, rivers, rain, snow, throughfall, fine particulate matter (PM_2.5), and wastewater treatment plant effluents in South Korea, which are reviewed in this manuscript. In summary, (1) stream and river carbon in South Korea are largely derived from the chemical weathering of soils and rocks, and organic compounds in plants and soils, strongly influenced by precipitation, wastewater treatment effluents, agricultural land use, soil water, and groundwater. (2) Unprecedentedly high Δ¹⁴C of precipitation during winter has been reported, which can directly and indirectly influence stream and river carbon. Although we cannot exclude the possibility of local contamination sources of high Δ¹⁴C, the results suggest that stream dissolved organic carbon could be older than previously thought, warranting future studies. (3) The ¹⁴C analysis has also been applied to quantify the sources of forest throughfall and PM_2.5, providing new insights. The ¹⁴C data on a variety of ecosystems will be valuable not only to track the pollutants derived from fossil carbon but also to improve our understanding of climate change and provide solutions.

• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.241-250
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• 2009

During the past few years, titanium salts were investigated as alternative coagulants for the removal of organic matter of different molecular sizes in contaminated water. The flocculation efficiency of Ti-salt was comparable to those of $FeCl_3$ and $Al_2(SO_4)_3$ salts, commonly used coagulants. Incinerated sludge-$TiO_2$ showed higher surface area and photocatalytic activity than commercially available $TiO_2$. Metal-doped forms were produced by adding coagulant aids such as iron (Fe-), aluminium (Al-) and (Ca-) calcium salts during Ti-salt flocculation to increase pH. Ca- and Al- doped $TiO_2$ showed very high photocatalytic activity compared to Fe-doped $TiO_2$. When tested in a pilot scale plant for treatment of dye wastewater to check practical feasibility of the novel process, the removal ratio of the chemical oxygen demand was comparable to those of commonly used coagulants but the settling of sludge was faster. The $TiO_2$ generated after sludge incineration showed a high photocatalytic activity for degradation of volatile organic compounds and increased the rate of hydrogen production by water photosplitting. $TiCl_4$ coagulant and $TiO_2$ produced from different water sources with different concentrations had low acute toxicity compared to heavy metals and commercial $TiO_2$ when examined based on D. Magna mortality. This paper presents the production, characterisation and the photoactivity of $TiO_2$ produced from Ti-salt flocculated sludge. Different case studies are discussed to highlighted recent advances in this field.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.362-367
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• 2006

Waste activated sludge(WAS) collected from domestic wastewater treatment plant is biomass that contains large quantities of organic matter. However, relevant literature show that the bio-hydrogen yield using WAS was too low. In this study, the effect of pretreatment of WAS on hydrogen yield was investigated. Pretreatment includes acid and alkali treatments, grinding, heating, ozone and ultrasound methods. After pretreatment organic matters of WAS were solubilized and soluble chemical oxygen demand(SCOD) was increased by 14.6 times. Batch experiments were conducted to investigate the effects of pre-treatment methods and buffer solution, hydrogen partial pressure, and sodium ion on hydrogen production from WAS by using heated anaerobic mixed cultures. Experimental results showed that addition of buffer solution, efficient pre-treatment method with alkali solution, and gas sparging condition markedly increased the hydrogen yield to 0.52 mmol $H_2/g$-DS.