• Journal of Environmental Science International
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• v.13 no.12
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• pp.1089-1102
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• 2004

Seasonal variation of biogeochemical characteristics was determined in Lake Shihwa from October 2002 to August 2003. When the lake was artificially constructed for the freshwater reservoir in 1988, the development of the strong haline density stratification resulted in two-layered system in water column and hypoxic/anoxic environment prevailed in the bottom layer due to oxidation of accumulated organic matters in the lake. Recently, seawater flux to the lake through the sluice has been increased to improve water quality in the lake since 2000, but seasonal stratification and hypoxic bottom layer of the lake still developed in the summer due to the nature of artificially enclosed lake system. As the lake is still receiving tremendous amount of organic matters and other pollutants from neighboring streams during the rainy summer season, limited seawater flux sluicing into the lake may not be enough for the physical and biogeochemical mass balance especially in the summer. The excess of accumulated organic matters in the bottom layer apparently exhausted dissolved oxygen and affected biogeochemical distributions and processes of organic and inorganic compounds in the stratified two-layered environment in the summer. During the summer, ammonia and dissolved organic carbon remarkably increased in the bottom layer due to the hypoxic/anoxic condition in the bottom layer. Phosphate also increased as the result of benthic flux from the bottom sediment. Meanwhile, dissolved organic carbon showed the highest value at the upstream area and decreased along the salinity gradient in the lake. In addition to the sources from the upstream, autochthonous origin of particulate organic carbon from algal bloom in the lake might be more important for sustaining aggravated water quality and development of deteriorated bottom environment in the summer. The removal of trace metals could be attributed to scavenging by strong insoluble metal-sulfide compounds in the hypoxic/anoxic bottom layer in the summer.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.69-77
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• 1997

A 12-cm long sediment core was collected from a station in Lake Shihwa where high salinity-anoxic deep water is isolated from low salinity-oxic surface water by a strong halocline barrier. Unprecedented concentrations of porewater ammonia and lead are encountered: at 9 cm sediment depth ammonia builds up to 1420 ${\mu}M$ and at 3 cm lead to 1348 nM. As they are stable in anoxic condition, high concentrations of ammonia and lead suggest a development of notorious anoxic condition in the benthic environment of the lake. The degree of pollution of the deep water is likely to be directly proportional to the magnitude of benthic flux, because the deep water is isolated from the surface water by the halocline. Apparent coincidence of the ammonia residence time in the deep water with the elapsing time after the completion of the artificial lake construction, as about three years, suggests that the deep water pollution is being progressed entirely by benthic flux at least with respect to ammonia. The residence time for lead is such a short 20 days that it suggests a rapid return of the bottom water lead, which is originated from porewater by benthic flux, back to sediments probably as metal sulfide phases. The speculation on the return of lead as sulfide phases is likely to be supported by high concentration of hydrogen sulfide in the deep water and by high sinking rate of non-organic particles in Lake Shihwa.

• KSBB Journal
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• v.23 no.1
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• pp.70-76
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• 2008

Surface of hydrophobic media was modified to become hydrophilic by ion beam irradiation. Fixed bed biofilm reactors packed with or without surface modification were used to remove organics, nitrogen, and phosphorus from sewage. This system composed of anoxic/oxic cycles to increase the nutrient removal. A cylindrical polyethylene was used as a packing media in this study. With 12 hours of hydraulic retention time (HRT), the reactors with and without surface modification showed 95% and 92% $COD_{cr}$ removal, respectively. Both reactors showed over 95% $COD_{cr}$ removals for a longer HRT of 16 hours. Nitrogen removal ranged 54.8% to 70.2% for the surface modified system and 57.5% to 76.5% for the non-modified system under same condition. Finally, phosphorus removal ranged 59.4% to 69.8% for the surface modified system and 51.3% to 63.4% for the non-modified system under same condition. From this study organics and phosphorus were better removed in using surface modified media and vice versa for nitrogen removal.

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.87-94
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• 2004

The effects of pretreatment of GAC and dissolved oxygen (DO) on the sorption capacity for ο-cresol were investigated using pretreated GAC under oxic and anoxic conditions. Virgin GAC was used with pretreated GACs by $O_2$, acid and base as sorbents. Sorption capacity of GAC was dependent on the oxygen conditions according to the pretreatment methods. Virgin GAC showed increased sorption capacity when DO was present in the solution, while $O_2$-pretreated GAC did not show any considerable capacity change. Acid- and base-pretreated GACs were relatively more influenced by presence of DO as compared with virgin GAC. Both acid and base-pretreated GACs showed a rapid sorption rate at the initial stage, but as contact time became longer the sorption was slower. Sorbed ο-cresol was extracted with micro-Soxhlet extraction apparatus using the GAC separated from the rate experiments. Within 1 hour both acid and base-pretreated GACs showed the decrease in extraction efficiencies under both oxic and anoxic conditions. After 1 hour such a trend (the increase as contact time was longer) was not observed and showed relatively constant efficiencies of 35∼50%. According to the results of this study $O_2$contacted with GAC before sorption as well as DO present in the solution during sorption could influence the GAC sorption capacity.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.1
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• pp.132-137
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• 2003

This study was carried out to investigate removal character of nitrogen and phosphorus with injection time of acetic acid on SBR, which is one of the biological treatment process. Wastewater used in experiment period was swine wastewater with character, relatively lower organic material concentration than nitrogen concentration. In the experiment with injection time of acetic acid, run 1 wasn't injected acetic acid during the anoxic period, and run 2 was injected intermittently acetic acid during the anoxic period of 15 hours. And run 3 was injected intermittently during the anoxic period of 3hours from end of wastewater filling. And filing time of the wastewater was 20hour from run 1 to run 3. In the study, the highest removal efficiency of organic and nitrogen were obtained by the operating condition of Run 2(the ratio of mixing/aeration time : 16.5/5.5, injection time of acetic acid : 15hours) and T-P was obtained by the operation condition of Run 3(the ratio of mixing/aeration time : 16.5/5.5, injection time of acetic acid : 3hours),and removal efficiency of $BOD_5$, $COD_{Mn}$, $COD_{Cr}$, T-N and T-P in the treated water was 96.1%, 87.7%, 90.6%, 86.6% and 84.5%, respectively.

• Economic and Environmental Geology
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• v.46 no.1
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• pp.39-50
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• 2013

The study area is located on the western coastal region of Korea, partly had been reclaimed lands. Groundwaters of the coastal area show lower Eh and DO values (Eh: 0.57 V ${\rightarrow}$ 0.13 V, DO; 9.7 mg/l ${\rightarrow}$ 1.3 mg/l), and higher Fe concentrations (> 20 mg/l) than those of the inner land (< 0.3 mg/l), indicating that the redox condition of groundwater changes from oxic into suboxic/anoxic conditions as it flows from the inland toward the coastal area. In addition, Fe speciation of groundwater from the coastal area demonstrates that the most dissolved Fe exist as $Fe^{2+}$, reflecting that groundwater is under the anoxic condition to sufficiently occur Fe reduction. According to the result of Fe extraction with the sediment samples from three wells (A, B, C), the sediments provide enough $Fe^{3+}$ to occur the Fe reduction in the groundwater. Integrated all results of the groundwater and sediment, we infer that the Fe reduction to occur in groundwater is associated with the reclamation processes of the study area.

• Journal of Animal Environmental Science
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• v.11 no.3
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• pp.189-196
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• 2005

This study was carried out to determine the acceptability of liquid manure bin among livestock farmers and agricultural farmers, and quantify its malodorous compounds. The results were as follows; 1. The size of the manure bins owned by $93\%$ of 60 farmers surveyed was 200 M/T and were all in normal operation. Around $57\%$ of the normally operated bins were processed under aerobic condition. 2. Filly percent of the respondents utilized their liquid manure bin twice a year while $64\%$ used commercial microbial products to enhance maturity of their liquid manure and abatement of malodorous emissions. On the other hand, $43\%$ mentioned problems on the labor requirement, mechanical maintenance and lending cost of liquid manure processing and utilization, and the price of the commercial microbial products. 3. Malodorants emitted from livestock liquid manure bins and their boundary bin depended upon the livestock liquid manure processing condition. Within bin under the aerobic processing condition, Iso-valeric and propionic acid were ranged 0.012 to 0.07ppm and 0.17 to 2.85ppm, respectively. Within bin under the anoxic processing condition, n-butyric, n-valeric acid, and acetaldehyde were ranged 1.5 to 2.3ppm, 1.3 to 1.8ppm, and 0.8 to 2.1ppm, respectively. Malodorants emitted from the boundary of livestock liquid manure bins under the anoxic processing condition were detected the range of 0.4 to 0.9 ppm, more than the concentration of law regulation, as an acetaldehyde, but under the aerobic processing condition, they did not any detection.

• Journal of Environmental Science International
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• v.21 no.12
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• pp.1455-1462
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• 2012

The vertical distributions of nitrifying bacteria in aerobic fixed biofilm were investigated to evaluate the relationship between nitrification performance and microbial community at different HRT. Fluorescent in situ hybridization (FISH) and portable ion selective microelectrode system were adopted to analyze microbial communities and ions profiles according to the biofilm depth. Cilia media packed MLE (Modified Ludzack-Ettinger) like reactor composed of anoxic, aerobic I/II was operated with synthetic wastewater having COD 200 mg/L and $NH_4{^+}$-N mg/L at HRT of 6 hrs and 4 hrs. Total biofilm thickness of aerobic I, II reactor at 4 hrs condition was over two times than that of 6 hrs condition due to the sufficient substrate supply at 4 hrs condition (6 hrs; aerobic I 380 ${\mu}m$ and II 400 ${\mu}m$, 4 hrs; aerobic I 830 ${\mu}m$ and II 1040 ${\mu}m$). As deepen the biofilm detection point, the ratio of ammonia oxidizing bacteria (AOB) was decreased while the ratio of nitrite oxidizing bacteria (NOB) was maintained similar distribution at both HRT condition. The ratio of AOB was higher at 4 hrs than 6 hrs condition and $NH_4{^+}$-N removal efficiency was also higher at 4 hrs with 89.2% than 65.4% of 6 hrs. However, the ratio of NOB was decreased when HRT was reduced from 6 hrs to 4 hrs and $NO_2{^-}$-N accumulation was observed at 4 hrs condition. Therefore, it is considered that insufficient HRT condition could supply sufficient substrate and enrichment of AOB in all depth of fixed biofilm but cause decrease of NOB and nitrite accumulation.

• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.7-24
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• 2008

Masan-Jinhae Bay, in Korea, is known for its frequent algal bloom outbreaks. This study was conducted in order to examine the environmental characteristics of the area, with the aim of identifying indicators that could be used to speculate about future algal blooms. The water temperatures and salinities in Haengam Bay, one of the small inner bays within Jinhae, appeared to re relatively higher than those in Masan and Jinhae bays, across most seasons. Furthermore, stratification begins to develop in all three regions from spring to summer as a result of the local heating effects and an increase in the efficient from the surrounding land. As a result, anoxic conditions appear near the bottom layer of the bay, leading to the deterioration of water quality, which has been identified as one of the causes of bloom outbreaks. Compared to Haengam and Jinhae bays, concentrations of DIN and DIP were remarkably higher in Masan Bay. However, the mean ratio of DIN to DIP was 3.3$\sim$13.6 in all three regions throughout the year, suggesting that nitrogen can function as a growth-limiting factor for phytoplankton. The results of mathematical models showed that cumulative organic pollutants may be a trigger for direct algal bloom occurrences, since residual tidal currents appeared to be less than $3\;cm\;\cdot\;s^{-1}$. Furthermore, computed DO concentrations in the four small inner bays of Jinhae during the summer appeared to be $3\;cm\;\cdot\;l^{-1}$ indicating a hypoxic state. Likewise, computed Chl-a concentrations turned out to be more than $0.01\;mg\;\cdot\;l^{-1}$, indicating eutrophication across most seasons. Based on the overall results, Masan-Jinhae Bay appeared to possess a very high potential for algal bloom outbreaks at anytime during the year.

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1826-1835
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• 2008

An autotrophic denitrification reactor (ADR-l) and a heterotrophic denitrification reactor (HDR-2) were operated to remove nitrate and nitrite in an anoxic environment in raw sewage. The $NO_3$-N removal rate of ADR-l was shown to range from 52.8% to 78.7%, which was higher than the $NO_3$-N removal rate of HDR-2. Specific denitrification rates (SDNR) of ADR-l and HDR-2 were 3.0 to 4.0 and 1.1 to $1.2\;mgNO_3$-N/gVSS/h, respectively. From results of restriction fragment length polymorphism (RFLP) of the 16S rRNA gene, Aquaspirillum metamorphum, Alcaligenes defragrans, and Azoarcus sp. were $\beta$-Proteobacteria that are affiliated with denitritying bacteria in the ADR-l. Specifically, Thiobacillus denitrificans was detected as an autotrophic denitrification bacteria. In HDR-2, the $\beta$-Proteobacteria such as Denitritying-Fe-oxidizing bacteria, Alcaligenes defragrans, Acidovorax sp., Azoarcus denitrificans, and Aquaspirillum metamorphum were the main bacteria related to denitrifying bacteria. The $\beta$-and $\alpha$-Proteobacteria were the important bacterial groups in ADR-l, whereas the $\beta$-Proteobacteria were the main bacterial group in HDR-2 based on results of fluorescent in situ hybridization (FISH). The number of Thiobacillus denitrificans increased in ADR-l during the operation period but not in HRD-2. Overall, the data presented here demonstrate that many heterotrophic denitritying bacteria coexisted with autotrophic denitrifying bacteria such as Thiobacillus denitrificans for nitrate removal in ADR-l. On the other hand, only heterotrophic denitritying bacteria were identified as dominant bacterial groups in HDR-2. Our research may provide a foundation for the complete nitrate removal in raw sewage of low-COD concentration under anoxic condition without any external organic carbon or the requirement of post-treatment.