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Seawater reverse osmosis (SWRO) has played a key role in alleviating water stress worldwide. However, its intensive energy consumption, which is highly dependent on fossil fuels, needs to be reduced to mitigate the CO2 emissions resulting from SWRO. Many technologies, including pressure-retarded osmosis (PRO), have been applied in an attempt to reduce the energy consumption of SWRO. In this study, potential trends in CO2 emissions from SWRO processes in Korea are considered based on SWRO operational data collected from a range of sources and relating to societal scenarios of the future. These societal scenarios are based on current population trends in Korea and the proportion of renewable energy currently utilized in Korea. Next, using a dimensionless performance index for the SWRO-PRO hybrid process, the study presents the potential efficacy of PRO in reducing the magnitude of CO2 emissions from SWRO processes in Korea. The analysis shows that CO2 may be reduced by 10%-40%. The results of the study suggest a promising role for PRO as a suppressor of CO2 emissions. It is anticipated that the study will facilitate further in-depth studies into the use of PRO. [ABSTRACT FROM AUTHOR]

It is essential that water resource management plans require explicit links across different spatial scales in a single watershed. This study aimed to identify existing gaps between sub-basin and watershed management strategies using a watershed simulation model soil and water assessment tool (SWAT). The SWAT was calibrated and validated at the upper and middle regions of the Yeongsan River in Korea using past weather inputs from 2012 to 2014. The simulation outputs from 2014 used as a reference were compared to those with future weather scenarios in 2032 produced from a regional climate model (RCM) such as RCM 2.6, 4.5, 6.0, and 8.5. We found that the calibration and validation results agreed well with the observed data, yielding Nash--Sutcliffe efficiency values more than 0.72 for daily streamflow as well as for monthly sediment and total phosphorus (TP) loads at the final watershed outlet. However, all projected weather data led to a significant difference in streamflow only at the sub-basin level, while all three variables at the watershed level varied significantly from scenario to scenario. These imply that water resource management plans determined at the watershed scale may not be suitable for those at the sub-basin scale, calling for a more refined search that harmonizes both management decisions. [ABSTRACT FROM AUTHOR]

Statistical analyses are often subject to misinterpretation due to poor data quality which is inaccurate, incomplete, or unavailable. This study describes how incomplete data diminishes the screening accuracy of water pollution hotspots using a self-organizing map (SOM), a popular algorithm in reducing the dimension of complex data in a nonlinear fashion. A full data set consisting of 12 water quality and quantity parameters monitored monthly over 3 years at the Yeongsan River in Korea was provided to SOM as a reference input. For purposes of comparison, SOM was further allowed to accept three incomplete data sets in terms of variable availability as well as data loss for single and multiple parameters and different pollution levels. We found that data loss of either single or multiple parameters exceeding 15% of the entire data set led to significant changes in spatial and temporal patterns of the original data. However, the variables intentionally unavailable in the given data set affected the screening performance of water pollution hotspots in SOM, to a less obvious extent, as long as the percentage of missing data fell below 10%. The same applied to data loss with three pollution levels, from high through moderate to low concentrations of one important variable. Therefore, we recommend the use of multiple approaches that couple dimensionality reduction algorithms with reasonable imputation methods for the data set with a high percentage (e.g. above 15%) of missing values. [ABSTRACT FROM AUTHOR]

Eutrophication is caused by the discharge of excess nutrients from various point and nonpoint sources. In particular, nonpoint sources of nutrients are difficult to identify because of diffuse sources and the effects of climate change. The objective of this study is to investigate the change in nutrient loading from land areas under climate change. In this study, the soil and water assessment tool (SWAT) model was applied to predict the sediment, total nitrogen (TN), and total phosphorus (TP) loads in the Yeongsan River Basin using geographical information (i.e., digital elevation map, land use, and soil type), observed data (i.e., meteorological data, streamflow, and water quality). Future climatic variables were obtained from a general circulation model, which was simulated using four representative concentration pathway (RCP) scenarios such as RCP 2.6, 4.5, 6.0, and 8.5. The results showed that flow rate, sediment load, TN load, and TP load were changed in terms of climate change under the different RCP scenarios. Impacts of climate change on a basin may be an important factor in eutrophication management in the Yeongsan River. The SWAT model provided an accurate prediction of the current nutrient pollutant loads and facilitated the reliable prediction of future nutrient pollutant loads under climate change. [ABSTRACT FROM AUTHOR]

Successful data analysis is an essential component of any environmental monitoring programs. This study introduces an effective data analysis method to identify water pollution hotspots as well as to drop redundant monitoring parameters and samples using a self-organizing map (SOM), which has a strong specialty in pattern extraction from complex monitoring data. A full data set consisted of nine parameters that were obtained on a monthly basis from 83 sites in various tributary streams along the Yeongsan River, Korea, from May 2011 to December 2015. The given data set was further partitioned into a number of subsets to examine their effect on variable importance and temporal pattern analysis. We found that water pollution hotspots were more clearly addressed in load-based SOM analysis than in concentration-based SOM analysis due to strong correlation between variables resulted from variability reduction by combining two variables into a single one for load analysis. In addition, the variables chemical oxygen demand and electrical conductivity and the parameters discharge and total nitrogen were found to participate most and least actively in describing spatial and temporal variation of the observed variables, respectively. About 35% of the sampling locations showed high similarity among the monthly data extending from November in the previous year to February in the following year. We believe that the proposed methodology can be useful in revising the upcoming water monitoring study by clarifying several issues related to monitoring parameters and frequency in the existing program. [ABSTRACT FROM AUTHOR]

This paper describes the effects of weir construction on water quality in the Yeongsan (YS) River. In general, weirs affect aquatic environments of rivers and streams by interrupting natural water flow. To identify changes in water quality before and after weir construction, analysis of variance and autocorrelation tests were conducted on data from four monitoring stations. Seasonal variations in suspended solids (SS), biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and pH were analyzed using data from six years of monitoring. No significant changes in mean BOD5 or COD followed the construction of weirs. However, mean TN and TP were changed significantly during and after construction. Moreover, SS and pH changed significantly during construction, and TN and TP concentrations were slightly improved after weir construction. However, continuous monitoring and analysis of water quality changes in each weir are required to prevent environmental disasters such as algal blooms. [ABSTRACT FROM AUTHOR]

The successful operation of a seawater reverse osmosis desalination plant depends greatly on the performance of the pretreatment step. The start-up of a pretreatment filtration process usually begins with a dynamic part called ripening, during which the filter media increases its adsorption ability and improves the removal of foulants from the seawater. In that period (typically lasting 30-60 min, depending on the system's conditions) the effluent often does not meet the quality requirements of the RO membranes and must often be disposed of. An observation and analysis of the ripening phenomena was performed using lab scale acrylic filter columns containing granular activated carbon. The seawater originated from the Yellow Sea in Korea and an inline coagulation was performed prior to filtration using an optimal dose of FeCl3 based on a jar test. The turbidity, total suspended solids concentration and dissolved organic carbon were measured before and after filtration with the goal of assessing the filtration performance. The filter media, which was cleaned and dried before filtration showed distinct ripening characteristics. The measurements were then used for parameter identification of a typical filtration model. Based on the fitted model one can predict the optimal filter depth that would reduce the waste stream production of the plant. [ABSTRACT FROM AUTHOR]

Seawater reverse osmosis (SWRO) desalination is considered one of the most promising technologies for supplying freshwater to the regions suffering from water scarcity. Although a considerable amount of research has been conducted in attempts to improve SWRO desalination technology, reducing the cost of producing freshwater is still required. In Korea, this effort is already been being carried out by the Seawater Engineering & Architecture of High Efficiency Reverse Osmosis (SeaHERO) project. Core Technology 2 (CT2), one of the most important sub-projects out of four CTs under SeaHERO, pursues two main goals: optimization of processes for low energy consumption/ high efficiency and localization of core parts/equipments of the SWRO plant. Four unit technologies (UTs) are then incorporated into CT2 and each UT has its own technical target; UT1 focuses on the development of SWRO desalination system integration and optimization technology in terms of energy saving; UT2 and 3 work to develop high performance RO membranes and 16-inch modules with polyamide-type materials and novel (i.e., non-polyamide) materials, respectively; UT4 works to develop a high-pressure/massive-capacity pump and hydrostatic energy recovery device for a high efficiency SWRO plant. Accordingly, the integration of the four UTs of CT2 in the SeaHERO project is expected to contribute to reducing the cost and energy consumption in producing freshwater from seawater using the SWRO process. [ABSTRACT FROM AUTHOR]

The present study proposes a methodology for determining the effective dispersion coefficient based on the field measurements performed in Gwangju (GJ) Creek in South Korea which is environmentally degraded by the artificial interferences such as weirs and culverts. Many previous works determining the dispersion coefficient were limited in application due to the complexity and artificial interferences in natural stream. Therefore, the sequential combination of N-Tank-In-Series (NTIS) model and Advection-Dispersion-Reaction (ADR) model was proposed for evaluating dispersion process in complex stream channel in this study. The series of water quality data were intensively monitored in the field to determine the effective dispersion coefficient of E. coli in rainy day. As a result, the suggested methodology reasonably estimates the dispersion coefficient for GJ Creek with 1.25m2/s. Also, the sequential combined method provided Number of tank-Velocity-Dispersion coefficient (NVD) curves for convenient evaluation of dispersion coefficient of other rivers or streams. Comparing the previous studies, the present methodology is quite general and simple for determining the effective dispersion coefficients which are applicable for other rivers and streams. [ABSTRACT FROM AUTHOR]

The objective of the present study was to conduct a preliminary assessment for perchlorate in surface water, drinking water, and wastewater treatment plant effluent samples obtained from the Nakdong and Yeongsan watersheds in the Republic of Korea. Samples were analyzed for perchlorate using ion chromatography with suppressed conductivity detection (IC-CD) and/or liquid chromatography with tandem mass spectrometry detection (LC-MS/MS). Method reporting limits were 5.0 μg/L for IC-CD and 0.05 μg/L for LC-MS/MS analysis. At perchlorate levels above 5.0 μg/L, IC-CD and LC-MS/MS provided comparable results. The levels of perchlorate detected in the samples procured from the Yeongsan watershed were <5.0 μg/L in each case. However, Nakdong watershed samples contained perchlorate at levels up to 60 μg/L. The highest concentrations of perchlorate were found in surface water samples, although drinking water contained perchlorate at concentrations up to 35 μg/L. In a subset of samples analyzed by LC-MS/MS, chlorate and bromate also were detected at concentrations ranging from <0.10 to 44 μg/L and <0.10 to 2.6 μg/L, respectively. To the best of the authors' knowledge, this is the first perchlorate assessment reported for water sources in the Republic of Korea. [ABSTRACT FROM AUTHOR]

While many current microbial source tracking (MST) methods rely on the use of specific molecular marker genes to identify sources of fecal contamination, these methods often fail to determine all point and nonpoint contributors of fecal inputs into waterways. In this study, we developed a new library-dependent MST method that uses pyrosequencing-derived shared operational taxonomy units (OTUs) to define sources of fecal contamination in waterways. A total 56,841 pyrosequencing reads of 16S rDNA obtained from the feces of humans and animals were evaluated and used to compare fecal microbial diversity in three freshwater samples obtained from the Yeongsan river basin in Jeonnam Province, South Korea. Sites included an urbanized agricultural area (Y1) (Escherichia coli counts ≥ 1600 CFU/100 mL), an open area (Y2) with no major industrial activities (940 CFU/100 mL), and a typical agricultural area (Y3) (= 1600 CFU/100 mL). Data analyses indicated that the majority of bacteria in the feces of humans and domesticated animals were comprised of members of the phyla Bacteroidetes or Firmicutes, whereas the majority of bacteria in wild goose feces and freshwater samples were classified to the phylum Proteobacteria. Analysis of OTUs shared between the fecal and environmental samples suggested that the potential sources of the fecal contamination at the sites were of human and swine origin. Quantification of fecal contamination was also examined by comparing the density of pyrosequencing reads in each fecal sample within shared OTUs. Taken together, our results indicated that analysis of shared OTUs derived from barcoded pyrosequencing reads provide the necessary resolution and discrimination to be useful as a next generation platform for microbial source tracking studies. [ABSTRACT FROM AUTHOR]

Multiplex PCR analyses of DNAs from genotypically unique Escherichia coli strains isolated from the feces of 138 humans and 376 domesticated animals from Jeonnam Province, South Korea, performed using primers specific for the chuA and yjaA genes and an unknown DNA fragment, TSPE4.C2, indicated that none of the strains belonged to E. coli phylogenetic group B2. In contrast, phylogenetic group B2 strains were detected in about 17% (8 of 48) of isolates from feces of 24 wild geese and in 3% (3 of 96) of isolates obtained from the Yeongsan River in Jeonnam Province, South Korea. The distribution of E. coli strains in phylogenetic groups A, B1, and D varied depending on the host examined, and there was no apparent seasonal variation in the distribution of strains in phylogenetic groups among the Yeongsan River isolates. The distribution of four virulence genes (eaeA, hIyA, stx1, and stx2) in isolates was also examined by using multiplex PCR. Virulence genes were detected in about 5% (38 of 707) of the total group of unique strains examined, with 24, 13, 13, and 9 strains containing hIyA, eaeA, stx2 and stx1, respectively. The virulence genes were most frequently present in phylogenetic group B1 strains isolated from beef cattle. Taken together, results of these studies indicate that E. coli strains in phylogenetic group B2 were rarely found in humans and domesticated animals in Jeonnam Province, South Korea, and that the majority of strains containing virulence genes belonged to phylogenetic group B! and were isolated from beef cattle. Results of this study also suggest that the relationship between the presence and types of virulence genes and phylogenetic groupings may differ among geographically distinct E. coli populations. [ABSTRACT FROM AUTHOR]