• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.302-307
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• 2009

물리적인 조류제어 기술에 해당하는 수류 차단막(이후 차단막)은 유입하천의 수류를 차단 또는 우회시켜 영양염류가 저수지의 유광층으로 공급되는 것을 차단하고 본류 수역으로의 조류 확산을 방지하는 기능이 있어 일본에서는 저수지 녹조제어 대책으로 자주 활용된 바 있다. 그러나 이러한 차단막은 국내 저수지와 같이 홍수시 유입 유속이 크고 수위변동이 심한 환경에서는 설치효과가 검증되지 않아 현장적용에 앞서 수치모의를 통한 효과 검증이 선행되어야 하며, 최적 규모와 위치 선정도 필요하다. 본 연구에서는 수위변동이 심한 국내 저수지 특성을 고려하여 차단막이 수위변화에 따라 상하로 이동할 수 있도록 기존 CE-QUAL-W2(이후W2) 모델의 알고리즘을 수정하고, 대청호에서 다양한 수리 수문조건에서 차단막의 기작과 효과를 예측하기 위해 가뭄년(2001년)과 평수년(2004, 2006년)을 대상으로 각각 모델을 적용하였다. 차단막 설치 예정지점은 소옥천 하류(7 m 깊이)와 댐으로부터 각각 14.9 km, 27.4 km 상류에 위치한 회남대교 아래 지점(10 m 깊이)과 대정리(10 m 깊이)로 가정하고, 모의 시나리오는 차단막을 설치하지 않은 경우(S-1), 소옥천 하류에 단독으로 설치한 경우(S-2), 소옥천과 대정리에 설치한 경우(S-3), 모든 지점에 설치한 경우(S-4)를 비교하였다. 차단막 설치에 따른 수문년 및 계절별 수질개선 효과(S-1에 대한 S-4 농도 저감 비)를 비교한 결과, 대청호에서 녹조문제가 가장 심각했던 2001년 6월$^{\sim}$8월 기간 동안 차단막은 봄-여름에 걸쳐 모든 비교 지점(회남, 댐, 추동, 문의수역)에서 Chl-a 농도를 최저(문의수역) 30%에서 최고(회남수역) 70% 정도 저감하는 효과를나타냈다. 평수년인 2004년과 2006년에는 강우사상에 따라 차단막 설치에 따른 Chl-a의 농도 저감 효과가 지점별로 다르게 나타났으며, 큰 강우사상이 6월, 7월, 8월에 걸쳐 골고루 발생한 2004년에 비해 7월 한 달 동안 집중된 2006년에 설치효과가 크게 나타났다. 수역별로 차단막의 설치효과를 비교해 보면, 유입수의 영향을 직접 받는 회남수역과 추동수역이 댐 앞과 문의수역에 비해 차단막 설치에 따른 Chl-a 농도의 저감 효과가 큰 것으로 나타났다. 그러나, 큰 홍수가 유입할 때 차단막 상류부에 집적된 조류의 일부가 수류의 포획(Entrainment) 기작에 의해 저수지 내부로 유입되는 것으로 확인되어 차단막 효과를 극대화하기 위해서는 홍수 전 차단막 상류부에 집적된 조류의 처리대책이 필요할 것으로 판단된다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1046-1047
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• 2015

기존에 시행 중인 도로교통 소음을 저감시키기 위한 방안인 방음벽과 저소음 포장은 보편적으로 사용되어 오고 있으나, 몇 가지 단점을 가지고 있다. 방음벽은 높은 시공으로 인한 도시 경관 저하, 과도한 시공비 및 유지비, 조류가 방음벽에 부딪혀 유발되는 생태계 교란 현상 등 여러 문제점을 가지고 있다. 또한, 저소음 배수성 포장은 타이어와 도로 포장간의 마찰 소음을 원천적으로 저감시키는 효율적인 공법이나, 시공 후 일정기간이 지나면 공극이 막혀 성능이 저하되어 유지 보수가 적절하게 필요한 단점이 있다. 수음점의 거리별 소음예측을 통하여 일반적인 원소음과 능동형 소음 저감 기술(ANC) 적용 후의 효과를 알아보고, 소음원의 제어 및 영향거리에 따른 저감 목표를 예측하고자 한다.

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.285-290
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• 2013

Recently a novel bio refinery process with using nonedible biomass, especially microalgae, has been developed in order to directly reduce $CO_2$ concentration from flue gas and simultaneously produce renewable bio fuel. Micro algae-to-biofuel processes are composed of microalgae cultivation, harvesting, lipid extraction, and bio fuel conversion. So, there are concerns about the energy efficiencies of bio refinery processes. In this study, the net energy ratio of microalgae processes were calculated for the microalgae produced from a pilot photobioreacto using $CO_2$ released from coal combustion. In this study, trans-esterification and pyrolysis processes were used to analyze the net energy efficiencies. Micro algae-to-biofuel processes might produce bio fuels with the higher energy than that of the total consumed energy for cultivation, harvesting, extraction and conversion. If the lipid content of microalgae was higher, the trans-esterification conversion process was more effective than that of pyrolysis process.

• Journal of Wetlands Research
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• v.15 no.1
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• pp.79-90
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• 2013

Stormwater wetland targeted to treat the rainfall runoff from cow feeding-lot basin has been monitored from May 2010 to November 2011. Reduction efficiency estimated based on 20 rainfall event monitoring was 88%, 54%, 70%, 31%, and 64% for TSS, BOD, $COD_{Cr}$, TN, and TP, respectively. Theoretically, as rainfall depth increases, hydraulic exchange ratio has to be increased. When the exchange ratio approaches to 1 (usually design goal), TSS reduction efficiency was estimated about 55%. Uncertainty in reduction efficiency of the stormwater wetland is normally very high due to the continuous rainfall activity, its magnitude and intensity, antecedent dry days, and other natural variables which can not be controlled by experiment conductors. In this study, predominant affecting variables was found to be hydraulics caused by consecutive rainfall events having different intensity and algal growth during dry days.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.67-73
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• 2017

For the bio-fuel conversion of algae, several processes are needed including cultivating, agglomeration, extracting and conversion to the bio-fuel. The production cost for each process makes the total production cost of algae bio-fuel conversion. The production cost of algae bio-fuel has still higher than that of the other commercial bio-fuel. The reduction of production cost for each process enables the competitive price as a bio-fuel. It is difficult to separate the algae from water because of the similar magnitude of density each other. The agglomeration and extracting of algae using ultrasonic wave is rare effect of environmental hazard and also it is appropriate technology for the next generation energy resources. The present research is investigated for the elucidation of algae behavior in the water with the ultrasonics wave. For this purpose, the unsteady computational fluid dynamic analysis has been conducted in the ultrasonic pressure field. The velocity, pressure and algae concentration changes with time have been analysed to clarify the mechanism of algae separation by ultrasonic wave.

• Journal of Korea Water Resources Association
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• v.56 no.3
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• pp.173-184
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• 2023

Due to climate change, algal blooms frequently occur not only in Korea but also around the world, and the risk of toxicity of harmful algae has recently been issued. It is known that the representative harmful algae, cyanobacteria, are caused by the intersection of three factors: water temperature, residence time, and nutrients. In this study, water quality simulation was carried out using EFDC, a three-dimensional numerical model, to analyze the variations in water quality due to the decrease of residence time according to the opening of Yeongju Dam in Naeseong-Cheon. In fact, the concentration of chlorophyll-a in Yeongju Dam in the summer of 2021 was significant, exceeding the 'algae warning' for a long time based on the previous algae warning system. On the other hand, as a result of performing the simulation under the condition that the dam gate was completely opened, the concentration of chlorophyll-a was mostly reduced below the 'algae warning' level during the simulation period. It was confirmed that reducing the residence time by restoring the flow of Naeseong-Cheon is a way to immediately reduce algae in Yeongju Dam.

• Journal of Life Science
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• v.31 no.10
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• pp.960-968
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• 2021

Since microalgae research started on late 18 century, they have been recognized as one of the most important bioresources used in bioindustry. Owing to the large efforts paid to industrial application of this microorganisms, their importance on food/feed and bioactive compounds has been further extending into the environmental research areas including alternative energy resources, mitigation of the carbon emission, and waste-water treatment. However, despite the importance on their industrial application, the fundamental research field related to the long-term preservation of microalgae culture has not received much attention. However, a less labor intensive and cost-efficient preservation technology enabling biologically active and stable microalgae-culture provides a key success factor in the biotechnological application. Therefore, this study investigated various cutting-edge microalgae cryopreservation technologies currently developed so far, mainly targeting Chlorophyta, which occupies the largest taxon in the classification system of microalgae. In addition, for the development of successful cryopreservation technique, the key factors such as temperature control effect and preservative effect during cryopreservation of microalgae culture were investigated. In addition, the problems with current preservation technology that is being used in Korean domestic biological resource banks and the international microalgal resource banks are described. According to our investigation, currently no standard method for long-term preservation of microalgae is available due to their various morphological and physiological characteristics. To overcome such issues, much more efforts on fundamental research area on the identification of specific biomarker used for microalgae taxonomical classification and further systemic approaches based on strain-specific cryopreservation methods needed.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.91-102
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• 2007

To anticipate and respond to harmful algae produced in a big artificial lake like Daecheong reservoir, development of a regional analysis computer system using GIS or RS technique is needed in addition to biological and chemical research. The purpose of this study is to develop a cyanobacterial blooming prediction model to prevent harmful algae produced in Daecheong reservoir and construct an early forecasting system based on GIS. For this purpose this paper examines previous studies related to the relationship between cyanobacteria and environmental factors in Daecheong reservoir and selects precipitation and air temperature as two important environmental factors for the development of cyanobacterial blooming prediction model. Data used in this study are water quality and weather data for three water regions in Daecheong reservoir between 2000 and 2004. Based on qualitative correlation analysis between cyanobacteria and environmental factors, this paper presents a Rump model which enables us to predict cyanobacteria in water regions of Daecheong reservoir. Under this model the prediction of initial occurrence time and growth period of cyanobacteria are possible. The model is also applied to the GIS-based early forecasting system for cyanobacteria, and finally a GIS which can predict cyanobacteria produced in Daecheong reservoir and can manage the related data is developed.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.65-71
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• 2010

In this study, we have evaluated biodegradability of diesel-oxygenates including DBM and gasoline-oxygenates having similar physio-chemical properties using indigenous aerobic microorganisms from a diesel-contaminated soil. Toluene and Ethanol have shown higher biological activity and the first-order degradation rate constants ranged around $0.11{\sim}0.3day^{-1}$. However, MTBE, gasoline-oxygenate has shown as a limited substrate. Moreover, As increased initial concentrations of DBM and TGME, degradation rates of those were decreased relatively. As a strategy to evaluate biodegradability of DBM and TGME, reduction of diesel-oxygenates, $CO_2$ production and toxicity by algae were monitored. This results indicated possible mineralization of diesel-oxygenates, But we could predict that residual byproduct produced even though complete consumption of diesel-oxygenates were observed if algal toxicity variation considered. In conclusion, it is the first report that diesel-oxygenates including DBM could be biodegraded effectively by indigenous soil microorganisms and this result increased the possibility of bioremediation technology to apply into oil-contaminated sites.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.9
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• pp.482-496
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• 2016

Algal blooms of cyanobacteria (blue-green Algae) due to the eutrophication of rivers and lakes can cause not only the damage by its biological toxins but also the economic loss in drinking water treatment. The natural algae coagulant, a commercial product known as W.H. containing the algicidal and allelopathic material derived from oak, can control algal problems proactively through the coagulation flotation process. However, because there have been no applications of the process for pre-treatment in drinking water plants, we could find no report on the optimum injection dose of W.H.. In this study, we have conducted several sets of jar-tests while changing W.H. dose and concentration of chl-a for (1) Han-river samples and (2) subcultured cyanobacteria samples, and monitored the removal mechanisms of algae intensively. Based on these jar-test results, two linear equations with variables of chl-a and turbidity have been deduced to predict the optimal W.H. dose after the multiple regression analysis using IBM-SPSS. Also, prototypes of automatic control logic have been suggested to inject the optimal W.H. dose promptly in response to the variation of water quality.