장민원 Min Won Jang , 조현경 Hyun Kyung Cho , 김상민 Sang Min Kim

DOI:10.15681/KSWE.2019.35.1.1 Vol.35(No.1) 1-8, 2019

The purpose of this study is to evaluate the nutritional status of Lake Jinyang using Landsat 8 satellite image band correlated with chlorophyll-a, which is also related to algae proliferation. We selected 20 Landsat 8 images dating from 2013 to 2017, taken close to water quality measurement date when the cloud cover was less than 20 %. Based on the results of the previous studies, analyzing the correlation between chlorophyll-a, and Landsat 8 satellite image band, we selected near infrared wavelength, band 5 which is closely related to the population of algae. The nutritional status was classified using the Aizaki trophic state index (TSIm). The results of the regression equation between band 5 and the observed chlorophyll-a data was used to calculate chlorophyll-a for the image data from 2013 to 2017. The concentration of chlorophyll-a ranged from 3 to 16.1 mg/m³. To illustrate the spatial distribution of chlorophyll-a within the lake, the chlorophyll-a concentration was divided into five grades. The images on October 14, 2014 and April 10, 2016 showed relatively high value of chlorophyll-a, while January 18, 2015 and December 6, 2016 chlorophyll-a value were below 5. The images on October 14, 2014 and April 10, 2016 were rated as eutrophic status in most areas. The results of simulating water quality for the day when the water quality was not measured resulted to an approximate value for the Panmun station while the Naedong station needed some corrections.

Aizaki trophic, Chlorophyll a, Eutrophication, Landsat 8, Nutritional status index

김수현 Kim Suhyun , 김정선 Kim Jungsun , 강임석 Kang Limseok

DOI:10.15681/KSWE.2019.35.1.9 Vol.35(No.1) 9-18, 2019

Recently, it was realized that a significant portion of pollution from urban areas originates from non-point sources such as construction sites, washoff from impervious surfaces, and sewage input from unsewered areas and combined sewer overflows. Especially, Urban stormwater runoff is one of the most extensive cause of the deterioration of the water quality in streams located in urban area. The objective of this study was to investigate runoff characteristics of non-point pollutants source at the urban area in the Suyeong River. Water quality variations were investigated at two points of Suyeong River during a period of 10 rainfall events. Concentration difference of non-point pollution source appeared big by precedent number of days of no rainfall. In addition, Event mean Concentration (EMCs) that well represents runoff characteristics of storm water during rainfall, was calculated, and runoff pollutants loading was also examined. The probability distribution of EMCs of BOD, COD, TOC, T-N, T-P, and TSS were analyzed and the mean values of observed EMC and the median values of estimated EMCs compared through probability distribution. Other objectives of this study were the characterization of discharge from non-point source, the analysis of the pollutant loads and an establishment of a management plan for non-point source of Suyeong River. Also, It was established that the most important thing for the administration of non-point pollution source is to come up with the solution for the reduction of effluent at the beginning.

Event mean Concentrations (EMCs), Nonpoint pollutants, Rainfall event, Suyeong River

김헌년 Hun Nyun Kim , 윤석제 Seok Jea Youn , 변명섭 Myeong Seop Byeon , 유순주 Soon Ju Yu , 임종권 Jong Kwon Im

DOI:10.15681/KSWE.2019.35.1.19 Vol.35(No.1) 19-27, 2019

The purpose of this study is to evaluate the water quality and phytoplankton community in Bukhan River which account for 44.4 % of the total inflow into Lake Paldang, using multivariate statistical techniques (i.e., correlation analysis, principal component analysis (PCA)/factor analysis (FA)). Water samples were collected from March to November 2015 and the following parameters measured; water temperature, pH, DO, EC, SS, BOD, Chl-a, COD, TN, NO₃-N, NH₃-N, TP, DTP, PO₄-P, and phytoplankton community. The water quality of the main stream and the tributaries were not significantly different apart from the relatively high concentration of BOD, COD and nutrients recorded in MH. The highest cell density of Stephanodiscus hantzschii and Merismopedia glauca dominated phytoplankton was observed in PD. Based on the correlation analysis, total phytoplankton and cyanophyceae were highly correlated with BOD, COD and nutrients. PCA/FA resulted in four main factors accounting for 82.240 % of the total variance in the water quality dataset. The group of component 1 (TN, DTN, DO, NO₃-N, water temperature) and component 2 (PO₄-P, T-P, DTP, SS) were classified as nutrient element factor whereas component 3 (Chl-a, COD, BOD, NH₃-N, pH) was related to organic substances. Hence, the identification of the main potential environmental pollution factors in Bukhan River will help policy makers make better and more informed decisions on how to improve the water quality.

Bukhan River, Multivariate analysis, Phytoplankton community, Water quality

유미나 Yu Mi Na , 변정환 Byun Jeong-hwan , 백준수 Baek Jun Soo , 윤석제 Youn Seok Jea , 유순주 Yu Soon-ju , 변명섭 Byeon Myeong Seop

DOI:10.15681/KSWE.2019.35.1.28 Vol.35(No.1) 28-34, 2019

This study analyzed the occurrence pattern of Dolichospermum (= Anabaena) in the Bukhan river from March 2012 to December 2014 in order to identify the genotypes of Dolichospermum. Furthermore, 16S rRNA were analyzed to identify the genotypes of Dolichospermum that occurred in 2015 which were then compared to the reference sequence deposited at NCBI. During this period, the occurrence of Dolichospermum was highly correlated to water temperature. In the year 2012 and 2013, Dolichospermum appeared in Lake Cheongpyeong (CP), Sambong (SB), and Lake Paldang (P2) between July and August. However, in 2014, it appeared in SB and P2, but not in CP. This reduction in appearance was attributed to the decreased inflow to Lake Uiam as a result of low rainfall in 2014 as compared to 2012. In July 2015, the Dolichospermum 16S rRNA genotype was confirmed in five locations; Lake Cheongpyeong (CP), Seojong (SJ), Songchon Sewage Treatment Plant (SC), Joan (P4), and Lake Paldang (PD). Anabaena crassa of spiral clone, A. planctonica of linear clone, and A. circinalis of spiral clone exhibited high genetic similarity with the reference sequence. The 16r RNA genotype showed approximately 3 % sequence variation between the locations and were more similar to each other in locations that were closer.

16S rRNA, Bukhan River, Dolichospermum sp., Genotype, PCR, Phylogenetic tree

백종석 Baek Jongseok , 이상진 Lee Sangjin , 신현석 Shin Hyunsuk , 김재문 Kim Jaemoon , 김형산 Kim Hyungsan

DOI:10.15681/KSWE.2019.35.1.35 Vol.35(No.1) 35-42, 2019

Urbanization has led to extreme changes in land use on urban watersheds. Most cities are becoming residential, commercial and industrial areas, making infiltration and storage of rainfall less favorable. The demand for LID (Low Impact Development) technology is increasing in order to mitigate this water cycle distortion and return to existing hydrological conditions. The LID technique is effective in reducing runoff by permeating the urban impervious area. However, considering the limit of the installation area and the financial requirement of the installation, there is not much research on the linkage of each LID component technology for optimum efficiency according to the appropriate scale. In this study, the effects of the LID facilities applied to the target site were simulated using the SWMM model, suggesting the optimal linkage method considering interconnectivity, and applying the effects as an existing installation of individual facilities. The water balance at the time of application of the LID technology, short-term and long-term rainfall event were compared. Also, the individual application and the linkage application were compared with each other. If each component technology has sufficient processing size, then linkage application is more effective than individual application.

EPA SWMM, LID, Linkage, Runoff, Urbanization

김호섭 Ho-sub Kim , 박윤희 Yun-hee Park , 김용삼 Yong-sam Kim , 김상용 Sang-yong Kim

DOI:10.15681/KSWE.2019.35.1.43 Vol.35(No.1) 43-54, 2019

The objective of this study was to assess the effect of policies on water quality management based on the changes in pollutants and water quality in Special Water Preservation Area (SWPA) of Lake Paldang watershed from 1990 to 2016. The population, total sewage and flow rate of wastewater in SWPA continuously increased from 1990 to 2016, while the location of new facilities for industrial and livestock facilities has been restricted. However, unlike the buffer zone in which industrial and livestock facilities were continuously reduced after implementing of TMDL, it was found that the effect of land-use regulations on industrial and livestock facilities in SWPA were mitigated by the increase in the size of large facilities. Since 1999 when the emission standard of public sewage treatment plants (STP) was changed, the water quality of Lake Paldang has increased despite the increase of pollutant source. Since emission standard of STP changed in 2012 (BOD 5 mg/L, TP 0.2 mg/L), BOD concentration in Lake Paldang has also improved to the level of water quality in the early 1990s where as TP concentration has remained at its lowest since 1990. BOD and TP average discharge concentration of 43 STP (≥ 500 m3/day) in 2016 have been maintained 1.7 ± 0.7 mg/L and 0.06 ± 0.02 mg/L respectively. While the discharged load of STP in SWPA was decreased by the concentration management, the contribution rate to the total discharged load of non-point pollutants increased to 70 % in 2015, and the contribution rate to the point discharged load of individual treatment facilities increased to 80 %.

Buffer zone, Emission standard, Lake Paldang, Land-use regulation, Public sewage treatment plant(STP), Special water preservation area (SWPA)

김경섭 Kyung Sub Kim

DOI:10.15681/KSWE.2019.35.1.55 Vol.35(No.1) 55-63, 2019

The Four Major Rivers Restoration Project started in 2009 and completed in early 2013 is a large-scale inter-ministry SOC project investing ₩22.2 10¹² and one of the Project’s objectives was to enhance the water-quality grade through recovering the river eco-system and environment. The average concentration and probability distribution of water-quality constituents at given and selected sampling sites are very significant elements for analyzing and controlling the water-quality of rivers or reservoirs effectively. Average concentration can be estimated by point estimator, distribution function of water-quality constituents or Bootstrap method, in which the distribution function estimated with more data in case of insufficient dataset, is applied. Ipo and Gangcheon water-quality monitoring stations in South Han River were selected to compare and analyze the variation of concentration before and after Ipo and Gangcheon Weirs construction, using the whole 4-year’s data, from 2005 to 2008 and from 2014 to 2017. Water-quality constituents such as BOD and COD relating to oxygen demanding wastes and TP and Chlorophyll-a relating to the process of nutrient enrichment called eutrophication were also selected. The guidelines for water-quality control and management after weir construction including evaluation of water-quality constituents’ variations can be presented by this paper.

Average concentration, Probability distribution, South Han River, Water-quality constituents variations, Weir construction

양종원 Yang Jong-won , 최용호 Choi Yong-ho , 채인석 Chae In-seok , 김미숙 Kim Mi-sug , 정용훈 Jeong Yong-hoon , 김태금 Kim Tae-geum , 곽동희 Kwak Dong-heui

DOI:10.15681/KSWE.2019.35.1.64 Vol.35(No.1) 64-71, 2019

In recent years, carbon dioxide (CO₂) bubbles emerged as the most widely applied material with the recycling of sequestrated storage to decrease global warming. Flotation using CO₂ as an alternative to air could be effective in overcoming the high power consumption in the dissolved air flotation (DAF) process. The comparison of DAF and DCF system indicated that, the carbon dioxide flotation (DCF) system with pressurized CO₂ only requires 1.5 ~ 2.0 atm, while the DAF system requires 3.0 ~ 6.0 atm. In a bid to understand the characteristics of particle separation, the single collector collision (SCC) model was used and a series of simulations were conducted to compare the differences of collision and flotation between CO₂ bubbles and air bubbles. In addition, laboratory experiments were sequentially done to verify the simulation results of the SCC model. Based on the simulation results, surfactant injection, which is known to decrease bubble size, cloud improved the collision efficiency of CO₂ bubbles similar to that of air bubbles. Furthermore, the results of the flotation experiments showed similar results with the simulation of the SCC model under anionic surfactant injection. The findings led us to conclude that CO₂ bubbles can be an alternative to air bubbles and a promising material as a collector to separate particles in the water and wastewater.

Bubble, Carbon dioxide, Collision, Dissolved air flotation, Flotation

전지홍 Ji-hong Jeon , 정광욱 Kwang-wook Jung

DOI:10.15681/KSWE.2019.35.1.72 Vol.35(No.1) 72-77, 2019

Soil type in LID infiltration practices plays a major role in runoff reduction efficacy. In this study, the effects of infiltration rate of foundation ground under bioretention on annual runoff reduction rate was evaluated using LIDMOD3 which is a simple excel based model for evaluating LID practices. A bioretention area of about 3.2 % was required to capture surface runoff from an impervious area for a 25.4 mm rainfall event. The relative error of runoff from bioretention using LIDMOD3 is 10 % less than that of SWMM5.1 for a total rainfall event of 257.1 mm during the period of Aug. 1 ~ 18, 2017, hence, the applicability of LIDMOD3 was confirmed. Annual runoff reduction rates for the period 2008 ~ 2017 were evaluated for various infiltration rates of foundation ground under the bioretention which ranged from 0.001 to 0.600 m/day and were converted to annual runoff reduction for hydrologic soil group. The runoff reduction rates within hydrologic soil group C and D were steeply increased through increased infiltration rate but not steep within hydrologic A and B with reduction rates ranging from 53 ~ 68 %. The estimated time required to completely empty a bioretention which has a storage depth of 0.632 m is 3.5 ~ 6.9 days and we could assume that the annual average of antecedent rainfall is longer than 3.5 ~ 6.9 days. Therefore, we recommended B type as the minimum hydrologic soil group installed LID infiltration practices for high runoff reduction rate.

Bioretention, Infiltration rate, LID infiltration practices, LIDMOD, Low Impact Development