공동수 Dongsoo Kong , 김진영 Jin Young Kim

DOI:10.15681/KSWE.2016.32.1.1 Vol.32(No.1) 1-14, 2016

This study was conducted to develop a Benthic macroinvertebrates streambed index (BMSI) based on the response of the community to the substrate type of streambed. Analyzing the seasonal (Spring and Fall) data (11,367 sampling units) surveyed and collected during 2008~2014 at 960 sites in South Korea, we estimated the lithophility of 191 taxa. BMSI was composed of the lithophilic value, indicator weight value and individual abundance frequency. It showed an extremely significant correlation (r = -0.8, p<0.001) with the mean grain size (in phi-value) of the streambed.

Benthic macroinvertebrates, BMSI, Physical habitat, Streambed, Substratum

김필재 Piljae Kim , 김진영 Jinyoung Kim , 손세환 Sehwan Son , 원두희 Doohee Won , 공동수 Dongsoo Kong

DOI:10.15681/KSWE.2016.32.1.15 Vol.32(No.1) 15-22, 2016

This study aims to analyze the changes in the benthic macroinvertebrate community before and after a restoration project in a eutrophic stream. Species diversity and species richness increased at the points where the channel changed from standing water to running water. However, species diversity and richness decreased at the points where only riparian restoration was implemented, and the concentration of suspended solids increased, while biochemical oxygen demand and total phosphorus decreased and the concentration of dissolved oxygen increased. In such reaches, functional feeding groups went from collector-filterers to collector-gatherers, and habitat orientation groups changed from clingers to burrowers.

Benthic macroinvertebrate, Kyoungan Stream, Restoration, Species diversity

이철규 Cheal Gyu Lee

DOI:10.15681/KSWE.2016.32.1.23 Vol.32(No.1) 23-29, 2016

Ozonation was investigated for its ability to remove pyruvic acid in a laboratory-scale batch reactor under various experimental conditions, including UV irradiation, TiO2 addition, and variations in temperature. An ozone flow rate of 1.0 L min-1 and a concentration of 75±5 mg L-1 were maintained throughout the experiment, and pH, COD, and TOC were measured at 10 min intervals during a 60 min reaction. Our results confirmed that the combination of UV irradiation and photocatalytic TiO2 in the ozonation reaction improved the removal efficiency of both COD and TOC in aqueous solution at 20°C. Pseudo first-order rate constants and activation energies were quantified based on the COD and TOC measurements. We observed that the O3/UV, O3/UV/TiO2 system increased mineralization and reduced the activation energy (Ea) necessary for pyruvic acid decomposition.

Activation energy, Ozonation, Pyruvic acid, TiO2 photocatalyst

유기경 Gigyung Yu , 최지연 Jiyeon Choi , 강희만 Hee Man Kang , 김이형 Lee Hyung Kim

DOI:10.15681/KSWE.2016.32.1.30 Vol.32(No.1) 30-35, 2016

Urban areas generate large amounts of stormwater and non-point source (NPS) pollutants during rainfall events. These are caused by various land use runoffs, vehicular and human activities and increased impervious cover. The increased runoff and NPS pollutants cause water quality deterioration in the receiving waters and adversely affect the aqua-ecosystem. These environmental impacts could be reduced through the application of low impact development (LID) techniques. In Korea, more than 80% of the total rainfall occurs in summer and most of these were 10 mm or less. Therefore, if the LIDs developed were able to cope with rainfall of 10 mm and below, NPS management could be efficiently conducted. This research was performed to determine the effect of varying amounts of rainfall on the performance capability of an established infiltration and filtration facility (IF facility) that can be applied to Korea’s common rainfall ranges. The IF facility area was 1.75% of the catchment area, however the facility treated more than 40% and 60% runoff volume and pollutant reduction respectively for a 10 mm rainfall. Lastly, higher volume and pollutant reduction could be attained when the LID area was at least 2% of the entire catchment.

Infiltration and filtration facility, IF facility, Low impact development, LID, Rainfall range, Removal efficiency

Ezequiel Q. Segismundo , 이병식 Byung Sik Lee , 김이형 Lee Hyung Kim , 구본홍 Bon Hong Koo

DOI:10.15681/KSWE.2016.32.1.36 Vol.32(No.1) 36-45, 2016

Sand filters are widely used in infiltration systems to manage polluted urban runoff. Clogging, which is mainly caused by the deposition of sediments on the filter media, reduces the filter system’s infiltration capacity, which further limits its lifespan and function. The physical, chemical and biological clogging characteristics of sand filter, therefore, need to be known for effective design and maintenance. Physical clogging behavior and variations in the characteristics of sand filters according to different media depths are examined in this paper. The variations were observed from laboratory column infiltration tests conducted in a vertical flow and fluctuating head condition. It can be seen that an increase in filter media depth results in a high sediment removal performance; however, it leads to a shorter lifespan due to clogging. In the choice of filter media depth to be used in field applications, therefore, the purpose of facilities as well as maintenance costs need to be considered. At all filter media depth configurations, premature clogging occurred because sediments of 100~250 μm clogged the top 15% of filter media depth. Thus, scrapping the top 15% of filter media may be suggested as the first operational maintenance process for the infiltration system.

Filter media depth, Infiltration, Physical clogging, Sand filter, Stormwater management

이명규 Myung Kyu Lee , 장준원 Jun Won Jang , 박성직 Sung Jik Park , 박재우 Jae Woo Park

DOI:10.15681/KSWE.2016.32.1.46 Vol.32(No.1) 46-51, 2016

In this study, we synthesized a combination of graphene oxide (GO) and titanium dioxide (TiO2) and confirm that GO can be used for CO2 photoreduction. TiO2 exhibited highly efficient combination with other conventional electric charges generated by these paration phenomenon for suppression of hole-electron recombination. This improved the efficiency of CO2 photoreduction. The synthetic form of GO-TiO2 used in this study was agraphene sheet surrounded by TiO2 powder. Efficiency and stability were enhanced by combination of GO and TiO2. In a CO2 photoreduction experiment, the highest CO conversion rate was 0.652 μmol/g·h in GO10-TiO2 (2.3-fold that of pure TiO2) and the highest CH4 production rate was 0.037 μmol/g·h in GO0.1-TiO2 (2.4-fold that of pure TiO2). GO enhances photocatalytic efficiency by functioning as a support and absorbent, and enabling charge separation. With increasing GO concentration, the CH4 level decreases to~45% due to decreased transfer of electrons. In this study, TiO2 together with GO yielded a different result than the normal doping effect and selective CO2 photoreduction.

CO2, Graphene oxide, Photocatalytic reduction, TiO2

류희성 Hui Seong Ryu , 박혜경 Hae Kyung Park , 이혜진 Hae Jin Lee , 신라영 Ra Young Shin , 천세억 Se Uk Cheon

DOI:10.15681/KSWE.2016.32.1.52 Vol.32(No.1) 52-59, 2016

This study investigated the occurrences and succession patterns of harmful cyanobacteria, as well as environmental factors, during a 3-year period (September 2012 to August 2015) in the upper region of the Nakdong River around Sangju weir. A total of 27 cyanobacterial taxa were observed in this study, and classified into 26 species and 1 variety belonging to 11 genera, 5 families, and 3 orders. Cell density ranged from 24 to 42,001 cells/ml, with a geometric mean of 33 cells/ml, during the survey period. The dominant orders differed depending on the survey year; order Oscillatoriales in 2013, Chroococcales in 2014 and Nostocales in 2015. An Aphanizomenon bloom occurred in June 2015 at which time the highest cell density of 36,873 cells/ml was detected in the upper region of the Nakdong River, where as the Aphanizomenon spp. cell density (190-1,704 cells/ml) had been low prior to that time. An Aphanizomenon bloom also occurred at around the same time downstream in the Young River, a major inflow branch of the Nakdong River. The Aphanizomenon cell density along the Nakdong River increased markedly after joining of the YoungRiver, indicating that the Aphanizomenon bloom in the YoungRiver caused a bloom in the Nakdong River. Meteorological and environmental parameters, such as very low precipitation, higher water temperature, pH, and TP concentration, and lower TN/TP ratio, in May and June of 2015 than in 2013 and 2014 exerted marked effects on the Aphanizomenon bloom in June 2015 in the Young River.

Aphanizomenon bloom, Cyanobacteria, Nakdong River, Nostocales

신용철 Yongchul Shin , 최경숙 Kyung Sook Choi , 정영훈 Younghun Jung , 양재의 Jae E. Yang , 임경재 Kyoung Jae Lim

DOI:10.15681/KSWE.2016.32.1.60 Vol.32(No.1) 60-69, 2016

In this study, we estimated root zone soil moisture dynamics using remotely sensed (RS) data. A soil moisture data assimilation scheme was used to derive the soil and root parameters from MODerate resolution Imaging Spectroradiometer (MODIS) data. Based on the estimated soil/root parameters and weather forcings, soil moisture dynamics were simulated at spatio-temporal scales based on a hydrological model. For calibration/validation, the Little Washita (LW13) in Oklahoma and Chungmi-cheon/Seolma-cheon sites were selected. The derived water retention curves matched the observations at LW 13. Also, the simulated soil moisture dynamics at these sites was in agreement with the Time Domain Reflectrometry (TDR)-based measurements. To test the applicability of this approach at ungauged regions, the soil/root parameters at the pixel where the Seolma-cheon site is located were derived from the calibrated MODIS-based (Chungmi-cheon) soil moisture data. Then, the simulated soil moisture was validated using the measurements at the Seolma-cheon site. The results were slightly overestimated compared to the measurements, but these findings support the applicability of this proposed approach in ungauged regions with predictable uncertainties. These findings showed the potential of this approach in Korea. Thus, this proposed approach can be used to assess root zone soil moisture dynamics at spatio-temporal scales across Korea, which comprises mountainous regions with dense forest.

Data assimilation, MODIS, Remotely sensed data, Root zone soil moisture, Soil and root parameters

신용철 Yongchul Shin , 최경숙 Kyung Sook Choi , 정영훈 Younghun Jung , 양재의 Jae E. Yang , 임경재 Kyoung Jae Lim

DOI:10.15681/KSWE.2016.32.1.70 Vol.32(No.1) 70-79, 2016

Based on the soil moisture data assimilation suggested in the first paper (I), we estimated root zone soil moisture and evaluated drought severity using remotely sensed (RS) data. We tested the impacts of various spatial resolutions on soil moisture variations, and the model outputs showed that resolutions of more than 2-3 km resulted in over-/under-estimation of soil moisture values. Thus, we derived the 2 km resolution-scaled soil moisture dynamics and assessed the drought severity at the study sites (Chungmi-cheon sites 1 and 2) based on the estimated soil/root parameters and weather forcings. The drought indices at the sites were affected mainly by precipitation during the spring season, while both the precipitation and land surface characteristics influence the spatial distribution of drought during the rainy season. Also, the drought severity showed a periodic cycle, but additional research on drought cycles should be conducted using long-term historical data. Our proposed approach enabled estimation of daily root zone soil moisture dynamics and evaluation of drought severity at various spatial scales using MODIS data. Thus, this approach will facilitate efficient management of water resources.

Drought, MODIS, Remotely sensed data, Root zone soil moisture, Soil and root parameters

오희균 Hee Kyun Oh , 이희찬 Hee Chan Lee

DOI:10.15681/KSWE.2016.32.1.80 Vol.32(No.1) 80-88, 2016

The main purpose of this study was to derive managerial priority for pollutants in drinking water using the Delphi technique and analytic hierarchy process (AHP) method. We collected fundamental existing items based on a literature review for water pollutants, and deduced a total of 36 sub-items from nine core sectors, as follows: organic matter; inorganic substances; pathogenic organisms; chemicals; heavy metals; radioactive substances; sediment deposits; heat; and oil, and then conducted the first round of an expert study to ensure that objective indicators properly evaluate major issues for management of for drinking water quality. In the following round, the necessity and importance assessments of adjusted items were implemented using a content validity ratio index. Finally, items modified by Delphi surveys were applied to AHP. We computed weighted values by pair-wise comparison of sub-items and each of five sectors modified by the second round. According to the results of AHP, the managerial priority for pollutants in drinking water was as follows; while heavy metal placed first in importance, pathogenic organisms came second, followed by inorganic substances, organic matter and chemical substances from the sector perspective.

AHP, Delphi technique, Drinking water, Pollutants

구자영 Ja Young Koo , 윤대순 Dae Soon Yoon , 이동준 Dong Jun Lee , 한정호 Jeong Ho Han , 정영훈 Younghun Jung , 양재의 Jae E Yang , 임경재 Kyoung Jae Lim

DOI:10.15681/KSWE.2016.32.1.89 Vol.32(No.1) 89-97, 2016

Digital Elevation Models (DEMs) have been used to represent the effects of topography on soil erosion. A DEM of 30 m resolution is frequently used in hydrology and soil erosion studies because the National Water Management Information System (WAMIS) provides a 30 m resolution DEM at national scale on its web site. However, the Ministry of Environment recommends the use of a DEM with 10 m resolution for evaluation of soil erosion due to the fact that soil erosion estimation is to some degree affected by the spatial resolution of DEM. In this regard, a DEM with 5 m resolution was resampled for 10 × 10 m, 20 × 20 m, 30 × 30 m, 50 × 50 m, 70 × 70 m, and 100 × 100 m resolutions, respectively. USLE LS factors and soil erosion values were evaluated using these datasets. Use of a DEM with at least 30 m resolution provided reasonable LS factors and soil erosion values at a watershed.

DEM, LS factor, Resolution, Topographic factor, Universal Soil Loss Equation, USLE

정헌재 Heon Jae Jung , 이보미 Bo Mi Lee , 이근헌 Keun Heon Lee , 신현상 Hyun Sang Shin , 허진 Jin Hur

DOI:10.15681/KSWE.2016.32.1.98 Vol.32(No.1) 98-107, 2016

This study examined the effects of environmental conditions and the presence of refractory organic matter on oxidation rates of total organic carbon (TOC) measurements based on high temperature combustion and ultraviolet-sulfate methods. Spectroscopic indices for prediction of oxidation rates were also explored using the UV spectra and fluorescence excitationemission matrix (EEM) of humic acids. Furthermore, optimum TOC instrument conditions were suggested by comparing oxidation rates of a standard TOC material under various conditions. Environmental conditions included salts, reduced ions, and suspended solids. Salts had the greatest influence on oxidation rates in the UV-sulfate method. However, no effect was detected in the high temperature combustion method. The UV-sulfate method showed lower humic substance oxidation rates, refractory natural organic matter, compared to the other methods. TOC oxidation rates for the UV-sulfate method were negatively correlated with higher specific-UV absorbance, humification index, and humic-like EEM peak intensities, suggesting that these spectroscopic indices could be used to predict TOC oxidation rates. TOC signals from instruments using the UV-sulfate method increased with increasing chamber temperature and increasing UV exposure durations. Signals were more sensitive to the former condition, suggesting that chamber temperature is important for improving the TOC oxidation rates of refractory organic matter.

Dissolved Organic Matter, DOM, Fluorescence, High temperature combustion, Spectroscopic indices, Total Organic Carbon, TOC, UV-persulfate

박윤식 Youn Shik Park , 금동혁 Donghyuk Kum , 이동준 Dong Jun Lee , 최중대 Joongdae Choi , 임경재 Kyoung Jae Lim , 김기성 Ki Sung Kim

DOI:10.15681/KSWE.2016.32.1.108 Vol.32(No.1) 108-114, 2016

Sediment-laden water leads to water quality degradation in streams; therefore, best management practices must be implemented in the source area to control nonpoint source pollution. Field monitoring was implemented to measure precipitation, direct runoff, and sediment concentrations at a control plot and straw-applied plot to examine the effect on sediment reduction in this study. A hydrology model, which employs Curve Number (CN) to estimate direct runoff and the Universal Soil Loss Equation to estimate soil loss, was selected. Twenty-five storm events from October 2010 to July 2012 were observed at the control plot, and 14 storm events from April 2011 to July 2011 at the straw-applied plot. CN was calibrated for direct runoff, and the Nash-Sutcliffe efficiency and coefficient of determination were 0.66 and 0.68 at the control plot. Direct runoff at the straw-applied plot was calibrated using the percentage direct runoff reduction. The estimated reduction in sediment load by direct runoff reduction calibration alone was acceptable. Therefore, direct runoff-sediment load behaviors in a hydrology model should be considered to estimate sediment load and the reduction thereof.

Best management practice, Curve number, Nonpoint source pollution, Surface cover