• Journal of Environmental Science International
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• v.4 no.3
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• pp.87-87
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• 1995

This study was investigated with denitrification of wastewater containing nitrate using upflow sludge blanket process. Contents of this study were the nitrogen gas Production, relationship between HRT and COD/$NO_3^--N$ ratio in case of various hydrogen donor addition, relationship between nitrate loading rate and various hydrogen donor addition.

• Journal of Environmental Science International
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• v.4 no.3
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• pp.239-247
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• 1995

This study was investigated with denitrification of wastewater containing nitrate using upflow sludge blanket process. Contents of this study were the nitrogen gas Production, relationship between HRT and COD/$NO_3^--N$ ratio in case of various hydrogen donor addition, relationship between nitrate loading rate and various hydrogen donor addition.

• Journal of Ecology and Environment
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• v.40 no.1
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• pp.66-74
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• 2016

Background: When developing water quality improvement strategies for eutrophic lakes, questions may arise about the relative importance of point sources and nonpoint sources of phosphorus. For example, there is some skepticism regarding the effectiveness of partial reductions in phosphorus loading; because phosphorus concentrations are too high in hypertrophic lakes, in-lake phosphorus concentrations might still remain within typical range for eutrophic lakes even after the reduction of phosphorus loading. For this study, water quality and the phytoplankton and zooplankton communities were monitored in a hypertrophic reservoir (Lake Wangsong) before and after the reduction of phosphorus loading from a point source (a sewage treatment plant) by the installation of a chemical phosphorus-removal process. Results: Before phosphorus removal, Lake Wangsong was classified as hypertrophic with a median phosphorus concentration of $0.232mg\;L^{-1}$ and a median chlorophyll-a concentration of $112mg\;L^{-1}$. The dominant phytoplankton were filamentous cyanobacteria for the most of the ice-free season. Following the installation of the advanced treatment process, phosphorus concentrations were reduced to $81mg\;L^{-1}$, and the N/P atomic ratio increased from 42 to 102. Chlorophyll-a concentrations decreased to $42{\mu}g\;L^{-1}$, and the duration of cyanobacterial dominance was confined to the summer season. Cyanobacteria in spring and autumn were replaced by diatoms and cryptomonads. Filamentous cyanobacteria in summer were replaced by colony-forming unicellular Microcystis spp. It was remarkable that zooplankton biomass increased despite the decrease in phytoplankton biomass, and especially cladoceran zooplankton which increased drastically. These responses to the reduction of point source P loading to Lake Wangsong imply that reducing the point source P loading can have a big impact even when nonpoint sources account for a large fraction of the total annual phosphorus loading. Conclusions: Our results also show that the phytoplankton community can shift to decreased cyanobacterial dominance and the zooplankton community can shift to higher cladoceran dominance, even when phosphorus concentrations remain within the typical range for eutrophic lakes following the reduction of phosphorus loading.

• Korean Journal of Environmental Agriculture
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• v.25 no.3
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• pp.247-256
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• 2006

This study has been conducted for the process of food wastes disposal using surplus capacity of established sewage treatment plant by co-digestion of fermented food wastes and sewage sludge after thermophilic acid fermentation of food wastes. The co-digestion of thermophilic acid fermented food wastes and sewage sludge was performed by semi-continous method in mesophilic anaerobic digestion reactor. It showed great digestion efficiency as the average SCOD and VS removal efficiency in organic loading rate 3.30g VS/L.d. were 74.2% and 73.6%, and the gas production rate and average methane content were 0.440 L/g $VS_{add}.d$ and 66.5%, respectively. Based on the results of this study, the co-digestion of thermophilic acid fermented food wastes and sewage sludge in sewage treatment plant is able to improve treatment efficiency of anaerobic digestion reactor and to dispose food wastes simultaneously, and was proved excellent economical efficiency comparing with any other treatment methods.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.1
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• pp.1-6
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• 2006

Biological nutrient removal(BNR) process used in this study, which was packed with EPS(expanded polystylene) media, has more many advantages in aspect of reducing hydraulic retention time(HRT) of the process and having less effect of temperature in the winter season than commercial process in the present. Bench-scale study was performed using domestic wastewater. In the results, it was observed that the T-N removal efficiencies in HRT 6 hr and HRT 4 hr were 55% and 51%, respectively, showing the small reduction (about 4%) of T-N removal efficiency according to shortening of HRT. In comparison of T-N removal characteristic in summer and winter seasons, it showed that T-N removal efficiencies in summer and winter seasons were 65% and 54%, respectively, showing the 11% lower T-N removal efficiency in winter season than in summer season due to deterioration of nitrification in winter season. In the studies of influent loading rate and C/N ratio, the process showed stable effluent quality under the condition of broad influent loading rate and C/N ratio. Therefore, it is anticipated that the developed process in this study could be applicable to small wastewater treatment plant in nutrient removal.

• International Journal of Concrete Structures and Materials
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• v.10 no.4
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• pp.407-424
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• 2016

This study tests ten full-size simple-supported beam specimens with the high-strength reinforcing steel bars (SD685 and SD785) using the four-point loading. The measured compressive strength of the concrete is in the range of 70-100 MPa. The main variable considered in the study is the shear-span to depth ratio. Based on the experimental data that include maximum shear crack width, residual shear crack width, angle of the main crack and shear drift ratio, a simplified equation are proposed to predict the shear deformation of the high-strength reinforced concrete (HSRC) beam member. Besides the post-earthquake damage assessment, these results can also be used to build the performance-based design for HSRC structures. And using the allowable shear stress at the peak maximum shear crack width of 0.4 and 1.0 mm to suggest the design formulas that can ensure service-ability (long-term loading) and reparability (short-term loading) for shear-critical HSRC beam members.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.66-73
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• 2004

Prototype crushed-stone compaction pile(${\Phi}=700mm$) were constructed on specific test site. Static loading tests for crushed-stone compaction piles were performed. Based on the static loading test results, finite element analysis was performed using software PENTAGON 3D. Numerical analysis were done for the area replacement ratio($a_s$) of $20{\sim}70%$ and $a_s$ was varied as a step of 10%. In the single crushed-stone compaction pile, settlement was decreased as $a_s$ was increased. In the group pile, this tendency was similar. In the in-sit test and numerical analysis, as $a_s$ increased, the stress concentration ratio was increased. But $a_s$ in the numerical analysis were more than that of in-situ test, greatly.

• Computers and Concrete
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• v.29 no.1
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• pp.47-57
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• 2022

The increase in waste tires has brought serious environmental problems. Using waste tires rubber particles as aggregate in concrete can reduce pollution and decrease the usage of natural aggregate. The paper describes an investigation on flexural bearing capacity of self-compacting concrete (SCC) pavement slabs containing crumb rubber. Cyclic loading tests with different stress ratios and loading frequencies are carried out on SCC pavement slabs containing crumb rubber. Based on Paris Law and test data, the fatigue life of SCC pavement slab containing crumb rubber is discussed, and a revised mathematical model is established to predict the fatigue life of SCC pavement slab containing crumb rubber. The model applies to different stress ratios and loading frequencies. The fatigue life of SCC pavement slab containing crumb rubber is affected by the stress ratio and loading frequency. The fatigue life increases with the increase of stress ratio and loading frequency. Real-time acoustic emission (AE) signals in the SCC pavement slab containing crumb rubber under cyclic loading are measured, and the characteristics of crack propagation in the SCC pavement slab containing crumb rubber under different stress ratios and loading frequencies are compared. The AE signals provide abundant information of fracture process zone and crack propagation. The variation of AE ringing count, energy and b-value show that the fracture process of SCC pavement slab containing crumb rubber is divided into three stages.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6A
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• pp.935-941
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• 2006

The hysteretic behavior of steel structure under cyclic and dynami loading such as earthquake is different to that under static loading. Because structural steels on dynamic deformation is different to static deformation with respect with mechanical characteristics and stress-strain relationship. Therefore, to accurately predict the hysteretic behavior of steel structures such as circular steel columns under cyclic and dynamic loading, the difference of loading carrying capacity and deformation according to loading rate, assumed static and dynamic deformation state, must be investigated. In this study, numerical analyses of circular steel column using SM490 for change of loading rate and diameter-thickness ratio(D/t) were carried out by using three-dimensional elastic-plastic finite element analysis and dynamic cyclic plasticity model of SM490 developed by the authors. Characteristics of hysteretic behavior of circular steel column using SM490, load carrying capacity and energy dissipation ratio, were clarified by analysis results.

• Journal of Korean Society of Water and Wastewater
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• v.26 no.6
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• pp.787-796
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• 2012

The purpose of this study is to investigate CSOs(combined sewer overflows) control in the combined sewer with/without separation wall. There is the high correlation between sewage velocity and suspended solid(SS) loading in the sewer without it. The SS/BOD ratio was about 3 times in the area with it, while it was about 5 times in the area without it. Therefore, the accumulated deposit within the sewer has influenced high SS loading in the sewer without it. This study showed that the separation wall installed acquired an acceptable efficiency in controlling the accumulated deposit in the combined sewer. According to this study, the BOD control effect was about 38 % in the sewer with the separation wall, whereas it showed about 24 % in the sewer without it. In this case, it was anticipated that the high pollutant control effect would be expected if the separation wall was installed in the combined sewer.