• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.142-142
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• 2023

Humans inevitably and continuously produce wastewater in daily life worldwide. To decrease the degradation of river water bodies and aquatic ecosystem therein, humans have built systems at different scales to collect, drain, and treat household-produced wastewater. Particularly, municipal wastewater treatment plants (WWTPs) with centralized controls have played a key role in reducing loads of nutrients in domestic wastewater for the last few decades. Notwithstanding such contributions, impaired rivers regarding water quality and habitat integrity still exist at the whole river basin scale. It is highly attributable to the absence of dilution capacity of receiving streams and/or the accumulation of the pollutant loads along flow paths. To improve the perspective for individual WWTPs assessment, the first crucial step is to achieve systematic understanding on spatial distribution characteristics of all WWTPs together in a given river basin. By taking the initiative, our former study showed spatial hierarchical distributions of WWTPs in three large urbanized river basins in Germany. In this study, we uncover how municipal WWTPs in the contiguous United States are distributed along river networks in a give river basin. The extended spatial scope allows to deal with wide ranges in geomorphological attributes, hydro-climatic conditions, and socio-economic status. Furthermore, we identify the relation of the findings with multiple factors related to human activities, such as the spatial distribution of human settlements, the degree of economy development, and the fraction of communities served by WWTPs. Generalizable patterns found in this study are expected to contribute to establishing viable management plans for recent water-environmental challenges caused by WWTP-discharges to river water bodies.

• 한국습지학회지
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• 제6권1호
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• pp.149-166
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• 2004

한강 하구의 염분 및 생태 환경에 관한 연구를 위하여 기존에 발표된 논문과 국립수산과학원의 국가해양환경측정망 자료를 이용하여 한강 하구의 염분 분포 특성을 구명하였으며, 염분과 연관하여 동식물플랑크톤, 저서생물 및 어류플랑크톤의 분포를 논의하였다. 염분의 시공간적 분포를 고려할 때 인천북항 주변 해역은 계절에 무관하게 연중 한강 유입수의 직접적인 영향을 받고 있으며, 담수 유입량이 많은 하계에는 팔미도 해역까지 담수 영향권이 확대되었다. 반면 해수의 직접적인 영향을 받는 상한선은 한강 본류인 경기도 김포시 고촌면 신곡리의 신곡수중보에 이르며, 해침이 상시적으로 발생하는 수역은 이보다 더 하류인 경기도 김포시 하성면 전류리로 판단된다. 동식물플랑크톤의 분포는 담수 및 해수 지역에서 혼재되어 분포하며, 일반적으로 염분의 분포 범위보다 훨씬 광범위한 분포를 보였다. 그러나 기수성 어류플랑크톤은 매우 제한된 수역에 분포하는 반면, 성어는 그 분포범위가 담수에서 해수에 이르는 광범위한 분포를 보였다. 경험적 분석에 의한 한강하구 환경의 문제점은 1)한강 하구 및 유수지역의 개발 압력에 따른 환경 파괴, 2)갯벌 매립에 의한 조간대 상실, 3)군사용 철책에 의한 육수전이환경(陸水轉移環境)의 생태적 단절이 매우 심각하였다.

• 한국환경과학회지
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• 제16권5호
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• pp.571-581
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• 2007

본 연구는 생태계 모델을 이용하여 수질오염이 심각한 시화호의 수질을 재현하고, 시화호 내로 유입하는 육상기원 오염부하량의 변동에 따른 시화호의 수질변화를 살펴보았다. 모델에 의해 계산된 화학적 산소요구량 결과는 관측치와의 상관성이 양호하였으며, 하천이 밀집한 호의 내측 수역에서 $8{\sim}9mg/L$의 높은 농도분포를 나타내었고, 방조제 수문이 위치한 남서쪽 수역에서 5 mg/L 내외의 가장 낮은 농도분포 특성을 보였다. 시화호로 유입하는 육상오염부하가 시화호의 수질에 미치는 영향을 살펴보았는데, 육상오염부하량을 95% 삭감시켜도 시화호의 화학적산소요구량 농도는 3 mg/L 내외로 계산되었으며, 이것은 해역생활환경 II등급 기준인 2mg/L를 초과하는 것으로써 육상으로부터 유입되는 오염부하의 삭감만으로는 수질개선에 한계가 있는 것으로 예측되었다. 한편, 퇴적물을 인위적으로 개선하여 퇴적물로부터 인과 질소의 용출량과 저층 산소소비율을 삭감시켰을 경우에 시화호 수질의 개선효과가 나타났다. 특히, 육상으로부터 유입하는 유기물 및 영양염류 부하와 퇴적물에 의한 영양염류 용출부하 및 산소소비율을 동시에 삭감하였을 경우에 시화호 내 대부분의 수역에서 $1.5{\sim}2.0mg/L$ 이내로 수질이 크게 개선되는 것으로 나타났다. 따라서, 시화호는 육상기원 오염부하량을 상당량 삭감하여도 목표수질 기준을 만족하기가 상당히 어려울 것으로 예측되었고, 퇴적물을 인위적으로 개선시키면 보다 뚜렷한 수질 개선의 효과를 얻을 수 있는 것으로 나타났다. 시화호 내측과 외측수역과의 해수 교환량이 적고 퇴적물의 오염이 심한 현 상태의 환경조건에서 해역생활환경 III등급 기준인 4 mg/L 이하를 달성하기 위한 시화호의 환경용량은 화학적산소요구량 기준으로 5 톤/일로 산정되었다. 향후 시화호의 수질관리를 위해서는 시화호를 포함한 유역별로 뚜렷한 개선목표를 설정하고 배출원별 할당부하량을 산정하여 오염물질 총량관리를 통해 시화호 주변 유역의 점원, 비점원 및 시화호 내퇴적물 등을 종합적으로 고려하여 관리해 나가야 할 것으로 판단된다.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.54-61
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• 2004

The engine-out flow is highly transient and hot, and may place tremendous thermal and inertial loads on a closed-coupled catalyst. Therefore, time-dependent and detailed flow and thermal field simulation may be crucial. The aim of this study is to develop combined chemical reaction and multi-dimensional fluid dynamic mathematical model and to study the effect of unsteady pulsating thermal and flow characteristics on thermal reliability of closed-coupled catalyst. The effect of cell density on the conversion performance under real running condition is also investigated. Unlike previous studies, the present study focuses on coupling between the problems of pulsating flow pattern and catalyst thermal response and conversion efficiency. The results are expressed in terms of temporal evolution of flow, pollutant and temperature distribution as well as transient characteristics of conversion efficiency. Fundamental understanding of the flow and thermal phenomena of closed-coupled catalyst under real running condition is presented. It is shown that instants of significantly low values of flow uniformity and conversion efficiency exist during exhaust blowdown and the temporal varaition of flow uniformity is very similar in pattern to one of conversion efficiency. It is also found that the location of hot spot in monolith is directly affected by transient flow pattern in closed-coupled catalyst.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.907-923
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• 2020

For the severe haze situation in the Beijing-Tianjin-Hebei region, conventional fine particulate matter (PM2.5) concentration prediction methods based on pollutant data face problems such as incomplete data, which may lead to poor prediction performance. Therefore, this paper proposes a method of predicting the PM2.5 concentration based on image analysis technology that combines image data, which can reflect the original weather conditions, with currently popular machine learning methods. First, based on local parameter estimation, autoregressive (AR) model analysis and local estimation of the increase in image blur, we extract features from the weather images using an approach inspired by free energy and a no-reference robust metric model. Next, we compare the coefficient energy and contrast difference of each pixel in the AR model and then use the percentages to calculate the image sharpness to derive the overall mass fraction. Furthermore, the results are compared. The relationship between residual value and PM2.5 concentration is fitted by generalized Gauss distribution (GGD) model. Finally, nonlinear mapping is performed via the wavelet neural network (WNN) method to obtain the PM2.5 concentration. Experimental results obtained on real data show that the proposed method offers an improved prediction accuracy and lower root mean square error (RMSE).

• 한국대기환경학회지
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• 제20권1호
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• pp.17-31
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• 2004

The subway play an important part in serious traffic problems. However, because subway system is a closed environment, many serious air pollution problems occurred in subway stations and injured passenger's health. Therefor, it is a necessary to identify sources and to estimate pollutant sources in order to protect passenger's health and to keep clean subway environment. The purpose of this study was to analyze a air quality in the subway stations and to apply a new receptor methodology for quantitatively estimate of PM10 sources. In this study, the size distributions of particulate matters has been measured by using Aerosizer LD (U.S.A., API, Inc.). It's real time measurement capability of time-of-flight technique offers a significant advantage of user convenience and air pollution management. Also, the mass concentrations of PM 10 has been measured by using mini-vol portable sampler (U.S.A., Airmetrics Co.). The sampling performed in Seoul subway stations during the period of February 2000 and April 2000. The number distribution data used in this study consisted of 26 raw data sets in the Jongno-sam-ga station. Correlation Analysis can be used in subway stations for source separation and identification. Then, number contribution from each source is determined by the particle number balance (PNB). The mass concentration data used in this study consisted of 31 raw data in the 8 different stations. The mass contributions of PM10 sources in the concourse by using PMF/CMB model.

• 환경위생공학
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• 제18권2호
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• pp.42-51
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• 2003

Public awareness of air pollution problem has increased the need for real time air pollution information system about changes in air pollution level. The purpose of this study is to construct e-AIR, a user-friendly air pollution information system for urban air quality using GIS(geographic information system) technology for windows. GIS was ideally suited featuring a geographical characteristics(e.g., road, traffics, buildings) and very effectively used in mapping and symbolization for the distribution of the spatial/periodic pollution status(e.g., pie or column chart, graduated symbols) which can be effectively applied to a information system on the web-site. And a user interface, GUI(graphic user interface) was designed very diversely and simply enabled the users connect with e-AIR and obtain a useful information of air quality. A interpretive technique, air pollution health index(e.g., PSI, AEI) was used also which transforms complex data on measured atmospheric pollutant concentrations into a single number or set of numbers in order to make the data more understandable. Eventually the final-step of this study was to construct e-AIR based on Web GIS could be assessed anywhere if internet is available and offer a very useful information services of the air pollution to the public like a weather news.

• 한국환경과학회지
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• 제26권6호
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• pp.711-717
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• 2017

Dielectric Barrier Discharge (DBD) plasma is a new technique for use in environmental pollutant degradation, which is characterized by the production of hydroxyl radicals as the primary degradation species. Due to the short lifetime of the chemically active species generated during the plasma reaction, the dissolution of the plasma gas has a significant effect on the reaction performance. The plasma reaction performance can be enhanced by combining the basic plasma reactor with a homogenizer system in which the bubbles are destroyed and turned into micro-bubbles. For this purpose, the improvement of the dissolution of plasma gas was evaluated by measuring the RNO (N-dimethyl-4-nitrosoaniline, an indicator of the generation of OH radicals). Experiments were conducted to evaluate the effects of the diameter, rotation speed, and height of the homogenizer, pore size, and number of the diffuser and the applied voltage on the plasma reaction. The results showed that the RNO removal efficiency of the plasma reactor combined with a homogenizer is two times higher than that of the conventional one. The optimum rotor size and rotation speed of the homogenizer were 15.1 mm, and 19,700 rpm, respectively. Except for the lowest pore size distribution of $10-16{\mu}m$, the pore size of the diffuser showed little effect on RNO removal.

• Journal of Advanced Marine Engineering and Technology
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• 제37권3호
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• pp.282-290
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• 2013

A primary air pollutant as an indicator of air quality released from incomplete combustion is Carbon monoxide. A study of the distributions of CO concentration with no heat source in a tunnel model closed at left end side is simulated with a commercial CFD code. The tunnel model is used to investigate the CO concentration distributions at three Reynolds numbers of 990, 1970, and 3290. which are computed by the inlet velocities of 0.3, 0.6 and 1.0 m/s. The CFD predictive approaches can be useful for a better design to analyze the distributions of CO concentrations. In the case of the tunnel model closed at left end side alone, the concentration changes of x/H=-5 and -2.5 have the similar laminar characteristics like the case of the tunnel model closed at both end sides expecially at low values of Reynolds number. Irregular average CO concentration variations at Re=1790 are considered that the transition from laminar to turbulent flow occurs even in three different tunnel models.

• 환경위생공학
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• 제22권4호
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• pp.23-32
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• 2007

Changes in the characteristics of dissolved organic matter was studied at selected stations in the Nakdong river basin using physical and chemical methods. Characteristics of dissolved organic matters were analysed and assessed. Production of disinfection byproducts were also investigated. Distribution of the organic compounds according to the Molecular weight(MW) indicate that MWs higher than 100K were highest with cattle excrement wastewater and MW between 100-10K were highest with waters from forest streams. Low MW compounds (Jess than 1K) were highest with the effluents from environmental facilities. Results of resin fractionation study show that acidic hydrophobic substances(AHS) were dominant in many stations. The values were higher in the samples from mainstreams and sidestreams where the influence of organic matter is higher than the water from environmental facilities. Hydrophilic neutral substances(HoN) such as hydrocarbon, pesticides and detergents were higher in the wastewater treatment facilities. HoN values of water from the forest streams were 4.7% indicating there is no synthetic pollutant.