• Journal of Power Electronics
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• v.14 no.2
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• pp.369-382
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• 2014

A growing dynamic electrical demand has created an increasing interest in utilizing nonconventional energy sources like Photovoltaic (PV), wind power, etc. In this context, this paper focuses on the design and development of a composite power controller (CPC) in the decoupled double synchronous reference frame (DDSRF) combining the advantages of direct power control (DPC) and voltage oriented control (VOC) for a PV sourced grid connected inverter. In addition, a controller with the inherent active filter configuration is tested with nonlinear and unbalanced loads at the point of common coupling in both grid connected and autonomous modes of operation. Furthermore, the loss and reactive power compensation due to a non-fundamental component is also incorporated in the design, and the developed DDSRF model subsequently allows independent active and reactive power control. The proposed developed model of the controller is also implemented using MATLAB-Simulink-ISE and a Xilinx system generator which evaluate both the simulated and experimental setups. The simulation and experimental results confirm the validity of the developed model. Further, simulation results for the DPC are also presented and compared with the proposed CPC to further bring out the salient features of the proposed work.

• Environmental Analysis Health and Toxicology
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• v.23 no.4
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• pp.267-276
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• 2008

Acute and chronic toxicities of sediment elutriate and surface water samples collected at Lake Shihwa were evaluated using standard toxicity testing organisms including Vibrio fischeri, Daphnia magna and Moina macrocopa. Acute exposure resulted in toxic effects in all surface water or sediment elutriate samples, except for those collected from the reed swamp and Okgu stream. The rainy season influenced the toxicity of the water samples, presumably either by dilution of point discharge or through introduction of non-point source contaminants through runoff. In the sediment, elutriate and surface water samples, copper was detected above potentially lethal concentration, which may in part explain the observed toxicity. Considering acute toxicities of the surface water streams that direct to the Lake Shihwa, efforts should be warranted to control and reduce discharge of point and non-point sources along Lake Shihwa.

• Journal of Applied Biological Chemistry
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• v.57 no.1
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• pp.95-101
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• 2014

Nonpoint pollution sources from agricultural activities are a major cause of water quality impairment. A nutrient management program utilizes farm practices that maintain efficient crop production systems and control agricultural nonpoint pollution sources. The objectives of present study were to identify appropriate best management practices (BMPs) according to changes of cropping system of main upland crop for reducing AGNPs loadings and to simulate the effects of the application of the several BMPs scenarios in Saemangeum watershed. The selected BMP scenarios were: 1) to convert naked barley and hulled barley to hairy vetch or chinese milk vetch, 2) to convert red pepper to soybean crop, and 3) to combine two scenarios, converting naked barley and hulled barley to hairy vetch or chinese milk vetch + converting red pepper to soybean crop. As a result of BMPs application, the crop requirement of nitrogen and phosphorus for upland crop reduced nitrogen by 41% and phosphorus by 47% in scenario 1, whereas scenario 2 reduced nitrogen by 30% and phosphorus by 23%. Overall, scenario 3 reduced nitrogen by 72% and phosphorus by 70% in agricultural non-point pollution sources associated with chemical fertilizer and livestock manure in Saemangeum watershed.

• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.500-505
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• 2004

While more attention has been paid in recent years to urban point source pollution control, no considerable measures have been taken to control urban non-point source pollution. Contaminants from non-point sources deposited on urban impermeable surfaces such as road and highway are easily released to the public waters by rainfall, leading to the deterioration in water quality in urban area. The present study investigated a system using filter media to reduce the level of contamination in urban road runoff. Three different media, designated as J-P (polypropylene, blowing type), B-P (polypropylene, fiber type), and P-F (Polyvinyl alcohol, cube and sheet type) were evaluated on the basis of pollutant removal efficiency as well as hydraulic property. Experiments were peformed using a 1/4-scale treatment unit at various pollutant roading and rainfall intensity with real rainwater runoff collected from road surfaces. The results at different rainfall intensities shows that the medium J-P is superior to the other media for water permeability. J-P was not blocked at 10 mm/hr rainfall and its permeability was stable. On the other hand, B-P and P-F resulted in substantial overflow ratio even at I mm/hr rainfall intensity. Comparing treatment efficiencies for suspended solids, all media showed similar removal ranged from 91 % to 95%. However, J-P seems to be better than the other media considering its higher water permeability. J-P and P-F, both hydrophobic, yielded over 76% of heavy metal removal. But, the hydrophilic media B-P showed much smaller removal ranging from 26% to 47%. This indicates that J-P and P-F are beneficial to remove heavy metal due to their hydrophobic property. The treatment efficiencies over PAHs (poly aromatic hydrocarbons) showed the similar removal efficiency ranging from 66% to 97% for all three media.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.69-78
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• 2009

In order to improve water quality of upper watershed of Paldang reservoir, it is necessary to evaluate non-point source pollution loads and identify critical watershed pollution sources. A GIS based Soil and Water Assessment Tool was applied to evaluate model application and reliability, estimate NPS pollution load, identify critical watershed by NPS pollution sources, and suggest various best management practices for Kyongan Stream watershed. Yearly NPS pollution loads were estimated 30.0% SS, 60.1% TN and 35.4% TP, respectably. The watershed pollution load is mainly decided by precipitation condition and SS and nutrients load have a significant regression relationship. Based on 10-year average yearly NPS pollution load, critical sub-watersheds were identified. The No. 5 and 17 which have lots of relatively intensive agricultural fields and scattered industrial area were vary critical sub-watersheds and under more intensive pollution load. In order to control critical watershed, watershed best management practices such as scientific fertilizer, contour farming and parallel terrace, transferring the sloppy farmland to grass or forest and constructing a buffer zone, and constructing wetlands and retention ponds will be applied. Overall the SWAT model can be efficiently used for identification of critical sub-watersheds in order to develop a priority watershed management plan to reduce water pollutions.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.5
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• pp.440-448
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• 2016

Nonpoint sources of pollution (NPS) is defined as diffuse discharges of pollutants (e.g., nutrient, pesticide, sediment, and enteric microorganism) throughout the natural environment and they are associated with a variety of farming practices. Previous studies found that water soluble anionic polyacrylamide (PAM) is one of the highly effective measures for enhancing infiltration, reducing runoff, preventing erosion, controlling nonpoint source of pollutants, and eventually protecting soil and water environment. Potential benefits of PAM treatment in agricultural soil and water environments have been revealed by many research and they include low cost, easy and quick application, and suitability for use with other Best Management Practices (BMPs) for NPS control. This study reviews the various applications of PAM and discusses its further potentials in agricultural environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.215-219
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• 2005

A macro spreadsheet model, WEANES (Wet Pond Annual Efficiency Simulation Model), has been developed to predict the long-term or annual removal efficiencies of wet retention/detention basins. The model uses historical, site-specific, multi-year, rainfall data, usually available from a nearby National Oceanic and Atmospheric Administration (NOAA) climatological station to estimate basin efficiencies which are calculated based on annual mass loads. Other required input parameters are: 1) watershed parameters; drainage area, pervious curve number, directly connected impervious area, and ti me of concentration, 2) pond parameters; control and overflow elevations, pond side slopes, surface areas at control elevation and pond bottom; 3) outlet structure parameters; 4) pollutant event mean concentrations; and 5) pond loss rate which is defined as the net loss due to evaporation, infiltration and water reuse. The model offers default options for parameters such as pollutant event mean concentrations and pond loss rate. The model can serve as a design, planning, and permitting tool for consulting engineers, planners and government regulators.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.2
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• pp.1-14
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• 2019

In rural areas, composting is a source of non-point pollutants. However, as the quantitative distribution and loading have not been estimated, it is difficult to determine the effect of composting on stream water quality. In this study, composting datum acquired by unmanned aerial vehicle(UAV) was verified by using terrestrial LiDAR, and the management status and load change of the composting was investigated by UAV with manual control flight, thereby obtaining the basic data to determine the effect on the water system. As a result of the comparative accuracy assessment based on terrestrial LiDAR, the difference in the digital surface model(DSM) was within 0.21m and the accuracy of the volume was 93.24%. We expect that the accuracy is sufficient to calculate and utilize the composting load acquired by UAV. Thus, the management status of composting can be investigated by UAV. As the total load change of composting were determined to be $1,172.16m^3$, $1,461.66m^3$, and $1,350.53m^3$, respectively, the load change of composting could be confirmed. We expect that the results of this study can contribute to efficient management of non-point source pollution by UAV.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.5
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• pp.763-770
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• 2006

The purpose of this study was to investigate the effects of mechanical(ball-mill) solubilization of excess sludge especially focused on the TSS(total suspended solid) reduction during the conventional aerobic digestion of sewage sludges including primary and/or excess sludge, HRT was examined at the 10 days and 20 days. According to the results of this study, TSS removal efficiency of solubilized excess sludge was almost two times higher than that of non-solubilized excess sludge. And as the proportion of the primary sludge increased, TSS removal efficiency became worse because primary sludge rarely contained microbial cells which could be easily solubilized physically. It was also proved that by the application of proper solubilization techniques to the excess sludge, HRT for the aerobic digestion could be lessened(above 50%) dramatically keeping the same or better digestion performance. The fact that between primary and excess sludges, only the excess sludge is quite effective in the sludge solubilization and in it's reduction says that excess sludge releasing sources are key-point in the sludge cake reduction field as a source control.

• Journal of Korean Society on Water Environment
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• v.32 no.6
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• pp.528-536
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• 2016

The purpose of Total Pollution Load Control at Tributary is to obtain maximum improvement effect of water quality through finding the most impaired section of water-body and establishing the proper control measure of pollutant load. This study was implemented to determine the optimal management of reach, period, condition, watershed, and pollution source and propose appropriate reduction practices using the Load duration curve (LDC) and field monitoring data. With the data of measurement, LDC analysis shows that the most impaired condition is reach V (G4~G5), E group (flow exceedance percentile 90~100%) and winter season. For this reason, winter season and low flow condition should be preferentially considered to restore water quality. The result of pollution analysis for the priority reach and period shows that agricultural nonpoint source loads from onion and garlic culture are most polluting. Therefore, it is concluded that agricultural reuse of surface effluent (storm-water runoff with non-point sources) and low impact farming that includes reducing fertilization and controlling the height of drainage outlet are efficient water quality management for this study watershed.