• Korean Journal of Environmental Biology
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• v.31 no.3
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• pp.213-224
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• 2013

Between May 2006 and November 2009, we investigated the relationship between fluctuations in environmental factors and phytoplankton communities in Saemangeum Artificial Lake, South Korea. Nutrient concentrations in the lake increased because of the inflow of water from Mankyung and Dongjin Rivers during the summer rainy season; in particular, high concentrations were detected at an inner zone close to the estuaries. During the summer rainy season, salinity at the inner zone reduced more rapidly than that at the other zones, and it was similar to the changes in nutrient concentrations. Variations in phytoplankton communities were caused by fluctuations in environmental factors: the abundance of phytoplankton at the inner zone was higher than that at the other zones. Diatoms were the dominant species in the phytoplankton communities. A small centric diatom, Skeletonema costatum like species, was predominant, with a mean abundance of 19.5% in Saemangeum lake. Because of accelerated eutrophication in the lake, phytoplankton abundance increased continuously and the total number of species present in the community decreased. In particular, some dinoflagellates could intermittently cause red tides during low temperature and salinity conditions (at the inner zone). In 2006~2007, a red tide-forming dinoflagellate, Prorocentrum minimum, was the predominant species, while Heterocapsa triquetra, Karlodinium veneficum, and Heterocapsa rotundata were the newly recorded species in late 2008 to early 2009. Therefore, the dynamics of phytoplankton communities under the perennially eutrophic conditions in Saemangeum lake appear to be primarily affected by changes in water temperature and salinity. In particular, the growth of harmful algae may have been accelerated by the low salinity and temperature conditions during the spring season at the inner zone.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.9 no.4
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• pp.179-195
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• 2004

The trophic state of the coastal waters of the southern part of Korea was assessed using biogeochemical data obtained from the National Marine Environmental Monitoring Program conducted by the National Fisheries Research and Development Institute for six years. The trophic state of different areas, analyzed by non-metric multi-dimensional scaling (MDS) analysis, could divide the areas into three groups. Masan Bay, with suboxic water masses and/or the highest concentrations of dissolved inorganic nitrogen and phosphorus occurred, was assessed as being in a hypertrophic state. Ulsan Bay, Onsan Bay, Busan and Jinhae Bay, located near strong point sources, were in a eutrophic state. Other areas, including Tongyong, Yosu, Mokpo and Jeju island, were evaluated as being in a mesotrophic state. During 1997 to 2002, the average values of excess nitrogen, which is the difference between the measured dissolved inorganic nitrogen (DIN) and the corrected DIN using the Redfield ratio, were positive at Ulsan, Onsan, and Busan, where there were inflows from polluted rivers. In contrast, those were negative values in Haengam Bay, Gwangyang Bay and nearby Yosu. This suggests that the limiting element for phytoplankton growth differed among sites. The time series data of excess nitrogen showed gradual decrease over time in the hypertrophic waters, but the opposite trend in the mesotrophic waters. This indicated that the ratio of nitrogen to phosphate varied according to the trophic state of the coastal waters. The enrichment of organic matter in sediment in eutrophic waters would disturb the normal pattern of biogeochemical cycling of nitrogen and phosphate. In order to assess the condition of the coastal environment, the benthic boundary layer should be considered.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.5
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• pp.713-721
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• 2012

In many instances phosphorus is a limiting factor for eutrophication in streams, and lakes. Because wastewater treatment plant itself may be the main phosphorus source in a natural water body, removal of phosphorus in final effluent of wastewater treatment processes is required. Amongst various technologies for phosphorus removal in wastewater, adsorption technology was investigated using activated Ca-loess complex. Ca was added in loess to enhance adsorption capacity and intensity of phosphorus. Ca added loess was activated at a high temperature of $400^{\circ}C$ which turned out to be the optimum temperature. Activated Ca-loess complex below $400^{\circ}C$ had not enough strength to be applied as an activated Ca-loess pallet column in wastewater treatment process. Ca-loess complex which activated above $400^{\circ}C$ lost its adsorption capacity as the loess surface was glassified when the activation temperature reached above $400^{\circ}C$20. Even if adsorption capacity of activated Ca-loess was not very high due to the lack of abundant pores on its surface, adsorption intensity was still high because it was activated with added Ca in loess. Activated loess was made by pallets. The activated loess pallets were filled in a column, and were applied in wastewater treatment process. Using an activated Ca-loess pallet column, total phosphorus (T-P) was reduced from about 0.5 mg/l to lower than 0.1 mg/l in wastewater treatment, and ionic phosphorus (phosphate) was completely removed for the four months of pilot plant operation.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.251-251
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• 2011

해양 투기가 금지되면서 혐기소화를 통해 최종적으로 발생되는 폐기물 양을 줄이고 메탄 등의 바이오 가스를 얻어 이를 에너지로 얻기 위한 많은 공정들이 현장에 적용되고 있다. 하지만 혐기 소화 과정을 마친 후 유출되는 유출액은 고농도의 유기물질 및 암모니아성 질소, 인산염 등을 다량으로 함유하고 있어 적은 양이라도 하천이나 호수 등에 유입되면 수질 악화와 부영양화를 초래할 위험성이 크다. 이번 연구에서는 음식물류 폐기물로부터 바이오가스를 생산하기 위한 혐기소화 공정에서 발생하는 유출액의 방류수 수질기준 확보와 경제성을 만족시킬 수 있는 처리공정의 상용화 기술을 개발하기 위해 생물학적 처리， 물리 화학적 처리를 통합한 공정을 적용하였다. P건설사 혐기소화 유출액 pilot plant(1 ton/day) 운전 결과 50~70% 로 $NO_2$-N 이 약 1,000 mg/$\ell$정도로 축적되는 현상을 보였으며 상대적으로 $COD_{Cr}$의 농도는 400~600 mg/$\ell$로 C/N 비가 낮아 탈질이 어려울 것으로 판단하였다. 이에 실험실 규모에서의 실험을 진행하였다. $NO_2$-N와 $NO_3$-N을 기준으로 McCarty 양론비 기준 80% 에서 300%까지 메탄올을 주입해 제조 폐수와 실제폐수로 실험을 진행하였고 제조폐수로 실행된 실험에서 아질산 탈질의 효율을 확인하였다. 미생물이 메탄올에 순응 후 완전 탈질에 걸리는 시간은 약 2.5 일로 확인 되었으며 메탄올이 추가로 주입되지 않은 반응조의 $NO_2$-N의 탈질량은 메탄올이 이론값 100% 주입 된 반응조에 비해 30% 이하의 처리 효율을 나타냈다. 이론값을 기준으로 메탄올이 100% 주입된 반응조는 약 96.1%의 탈질 효율을 보였으며 메탄올 순응 후에 약 1.5 일의 HRT가 단축되었기 때문에 메탄올에 장시간 순응 시 탈질 효율이 더 좋아질 것으로 보인다. 아질산탈질에 대한 실험실 규모 연구결과를 토대로 pilot plant에서 재현성 검토를 목적으로 운전을 수행하였다. 무산소조의 HRT는 2.7 일 이었으며 호기조의 HRT는 4.1 일 이었다. 유입수의 평균 $COD_{Cr}$ 농도는 2,878 mg/L, T - N 농도는 2,723 mg/L로 나타났으며 $NO_2$-N 기준 C/N비 1.2-1.8의 메탄올을 주입하였을 때 96% 이상의 탈질율을 보였다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.882-895
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• 1997

Changes in the benthic communities have been studied to investigate the environmental effects before and after the construction of Shihwa Dike in the West coast of Korea. It is suggested that sequential changes in macrofaunal assemblages progressed in two sucressional directions. In the Shihwa lake under the influence of organic enrichment. First, the appearance of 'azoic tone' or 'grossly polluted zone' developed in the area of less than 6 m in depth resulted from the severe dissolved oxygen depletion due to the eutrophication from the increased organic loading. Second, the 'polluted zone' characterized by the proliferation of the opportunistic species in organically enriched area, was found in the vicinity of the industrial discharges and nearby fluvial inputs. This benthic community succession in the Shihwa lake seemed to be caused by the various ecological events such as an eutrophication in this organically enriched environment after construction of the dike and other physico-chemical parameters like salinity and dissolved oxygen in the bottom water, which may be influenced by the irregular surface water discharge and dilution by outer seawater inflow through the water gate of the dike. On the other hand, the benthic communities in the outside of the dike showed that the species richness was more than doubled and the abundance increased almost seven times more than that before the dike construction. This may be a typical characteristics of the initial phase in benthic eutrophication, suggesting that an increased organic input area may have been reponsible for this faunal change in the study area.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.2
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• pp.143-148
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• 2011

In this work, a composite formed by adding loess with lanthanium ("La-Loess") was proposed for effective removal of phosphate found in confined water bodies such as lake and reservoir. It was found that the theoretical maximum amount of lanthanum that can be attached to Loess was 2.68 mg La/g Loess. The phosphate removal was enhanced as an added amount of La-Loess composite increased. Furthermore, there was a noticeable difference in phosphate removal between Loess and La-Loess as the latter required 1.5 to 10 times less Loess than the former. Both Isotherm equations of Freundlich and Langmuir can be used to explain the phosphate adsorption characteristics in using La-Loess composites. The phosphate removal was very effective in the pH range of 5~8, which means that the proposed adsorbent can be directly applied to natural water without adjusting pH. Also, the La-Loess composites were well settled within 30 min without causing turbidity in water. Consequently, the proposed La-Loess can be strongly recommended for phosphate removal in confined water bodies.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.943-952
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• 2013

Algae blooms have soared recently in the lakes across the nation due to eutrophication. Blue-green algae cause unpleasant scene, produce taste and odor problem, and hinder processes in drinking water treatment. Algae toxicity monitoring has been strengthened, because the damages of wild lives and livestocks by algal toxins have been reported. Investigation on the characteristics of cyanobacterial occurrence and concentration distribution of Cyanotoxins in Hoeya reservoir have been conducted. Physical and chemical influences of water environment on cyanobacterial occurrences have also been studied. Movements of four species of Microcystin and five species of Anatoxin-a among Cyanotoxins were observed by LC-MS/MS analysis. Microcystis spp. among the cyanobacteria have mainly dominated in the Hoeya reservoir during the investigating period. The density of cyanobacteria were positively correlated with temperature and pH of water. Highest concentrations of Microcystin-LR and Microcystin-RR were $0.424{\mu}g/L$ and $0.117{\mu}g/L$ at the sampling points. Total concentration of Cyanotoxins in water coming into the water treatment plant was $0.182{\mu}g/L$, and they were not detected in treated water.

• Microbiology and Biotechnology Letters
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• v.26 no.1
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• pp.76-82
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• 1998

The feasibility of algae as means of removing nitrogen and phosphorus from secondary treated swine wastewater was studied. Among the tested 7 species of Chlorella vulgaris (UTEX 265), Chlorella sp. GE 21, Botryococcus braunii (UTEX 572), Botryococcus sp. GE 24, Scenedesmus quadricauda, Phormidium sp. GE 2, and Spirulina maxima (UTEX 2342), C. vulgaris was selected for its fast growth and abilities to remove nitrogen and phosphorus and to produce algal biomass from swine wastewater. C. vulgaris grew well at 35$^{\circ}C$, and the optimum initial pH for growth was 8.0. In the effect of light intensity, the growth of C. vulgaris was limited under a light intensity of less than 40 ${\mu}$E/$m^2$/s. The secondary treated swine wastewater contained 58.7 mg/l of total nitrogen and 14.7 mg/l of total phosphorus, and was diluted to 75, 50, and 25% with groundwater to be treated. Nitrogen and phosphorus were removed by C. vulgaris in all diluted swine wastewaters among which the most effective removal was in 75% swine wastewater (swine wastewater:groundwater=3:1). There was a tendency of linear increase in nitrogen and phosphorus removal time with increasing concentration of swine wastewater. Under the optimized culture condition, total nitrogen and total phosphorus were effectively removed to 95.3% and 96.0%, respectively, in 25% swine wastewater after 4-day incubation.

• Applied Biological Chemistry
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• v.43 no.2
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• pp.124-129
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• 2000

Nitrogen and P in surface runoff and eroded sediment from cropland areas can contaminate streams and lakes. Runoff losses of N and P were determined in a small field plot $(14.3{\times}24.8\;m)$ of peach orchard from March to November in 1999. Nitrogen and P were applied in the rate of 172 and 46 kg/ha using chemical fertilizer and mixed oil cake fertilizer. During the season, in 26 rainfall events, $421.5\;m^3/ha$ of runoff including 1,989 kg/ha of soil loss was collected. Concentrations of total-N, $NO_3-N$, $NH_4-N$, total-P and $PO_4-P$ in runoff samples were in the range of $4.7{\sim}171.0,\;0.1{\sim}188.0,\;0.13{\sim}3.36$, $0.58{\sim}4.99$ and $0.05{\sim}3.71\;mg/l$, respectively. Total loss of N was 16.39 kg/ha and 75% of the loss was $NO_3-N$. Total loss of P was 1.04 kg/ha, and $PO_4-P$ and sediment bound P accounted for 47 and 27% of the total loss, respectively. The losses of N and P were about 9.5 and 2.3% of the applied N and P in the plot, respectively. Although the loss of N or P would be relatively small in agricultural aspect, considering the high concentrations of N and P in runoff, loss of N and P from croplands should be controlled to reduce the eutrophication problem of stream waters.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.101-106
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• 1999

The down-core distribution of chlorophyll a, organic carbon contents and ${\delta}^{13}C$ in the bottom sediments were measured to understand the evolution of eutrophication in Masan Bay. Bottom sediment were collected in January 1994. The chlorophyll a and organic carbon contents in the sediment core decreased with increasing sediment depth, respectively. Bottom sediments (0~20 cm) in Masan Bay was rich in chlorophyll a (avg. 9.6 ${\mu}g\;g^{-1}$ dryweight) and organic C (avg. 2.5%). The down-core distribution of chlorophyll a suggests that the inner part of Masan Bay has experienced the acceleration of chlorophyll a supply since 1960s. Flux of organic carbon to the sea floor is in the range of 10 $gCm^{-2}\;yr^{-1}$ assuming the C:Chl a ratio of 25. It suggests tht approximately 1.3% of the fixed carbon by phytoplankton appears to be deposited in the bottom sediments.