• KCID journal
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• v.21 no.1
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• pp.55-63
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• 2014

A sedimentation basin for agricultural water quality improvement was researched to analyze the water quality purification characteristics. The sedimentation basin constructed at the inlet of Gamdon reservoir in Muan-gun, Jeollanam-do was selected as the research field of this study. The surface area of the sedimentation basin is $34,000m^2$, volume is $122,000m^3$, and hydraulic retention time is 0.3hr~7.3day. The average influent loading of SS was 156.6kg-SS/d, and the effluent loading was 67.5kg-SS/d with the average removal rate of 56.9%. The average influent loadings of BOD and COD were 33.0kg-BOD/d and 60.3kg-COD/d respectively, and the effluent loadings were 26.4kg-BOD/d and 48.6kg-COD/d with the average removal rate of 20.1% and 19.3% respectively. Therefore, the results of this study show that a sedimentation basin can purify SS and organic matters. The average influent loadings of T-N and T-P were 28.7kg-TN/d and 2.97kg-TP/d respectively, and the effluent loadings were 16.3kg-TN/d and 1.41kg-TP/d with the average removal rate of 43.0% and 52.6% respectively. In conclusion, the overall results of this study show that a sedimentation basin is a feasible alternative to purify organic matters and nutrients.

• Magazine of the Korean Society of Agricultural Engineers
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• v.42 no.4
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• pp.87-95
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• 2000

A vegetation purification system was applied to improve water quality of Masan Reservoir in Korea, which was composed of constructed wetlands in series. Five different kinds of macrophytes were planted in each wetland. The system was operated with the condition of low concentrations and high hydraulic loadings. Removal efficiencies(%) of chemical oxygen demand(COD) , total nitrogen(T-N) and total phosphorus(T-P) in this system were 9.0, 12.8, 20.1% , respectively. and removal rates(g/$m^2$/d) were 1.9(COD), 0.34(T-N) and 0.05(T-P) . Comparing this system with other wetlands operated at low hydraulic loadings, average removal efficiencies were low but removal rates were relatively high. Accordingly, this system could be applied to imporve reservoir water quality, because removal rates are more important than removal efficiencies in case of reservoir water quality improvement . However, the removal efficiencies and rates of this system are less than those of the hydroponic biofilter method which is a kind of a constructed wetland and utilize root zones of emergent macrophytes for trapping pollutants. Therefore, it is recommended that this system should be modified to utilize root zones of emergent macrophytes enough to improve reservoir water quality more efficiently.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.91-96
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• 2006

Many small scale Sewage Treatment Plants (STPs) are currently being constructed at many rural areas. The STPs in rural area suffer from low concentration and large inflow quantity fluctuation during wet weather mainly due to illicit combined sewer system. Sequencing Batch Reactor (SBR) is a process effectively coping with these obstacles. The main objective of this study was to evaluate SBR with high hydraulic loading and low inflow concentration. The operating conditions tested were: organic loading rate = $0.17-0.42KgBOD/m^3/d$, hydraulic loadings = $12.1-61.5m^3/m^2/d$, average MLSS concentration = 2500 mg/L, F/M ratio = 0.026-0.17 KgBOD/Kg MLSS, HRT = 9-12 hr HRT, and SRT = 5.6-33.6 days. Organic loading rate on SBR did not impact significantly on BOD and SS removal efficiencies. To increase treatment efficiencies, low hydraulic loading rate with low concentration was required. The results suggested that low influent concentration with high inflow rates during wet weather requires extended time for settling.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.601-608
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• 2011

In order to design floating structures, it should be required to evaluate hydrodynamic motions and structural behavior under the wave loadings. Then, structural behavior of floating structures should be evaluated including the effects of wave-induced hydraulic pressure subjected to floating structures. However, there has been a problem to exactly evaluate structural behavior of floating structures since it was difficult to directly connect wave-induced hydraulic pressure resulting from hydrodynamic analysis with structural analysis model. In this study, in order to exactly evaluate structural behavior of floating structures under the wave loading, integrated analysis of hydrodynamic motion and structural behavior was carried out to the large-scaled floating structure. The wave-induced hydraulic pressure resulting from hydrodynamic analysis AQWA were directly mapped to structural analysis model ANSYS bia Workbench interface of ANSYS Inc.. As the results of this study, it was found that the integrated analysis of this study evaluate exactly structural behavior of floating structures under the wave loadings since this method can directly reflect wave-induced hydraulic pressure resulting from hydrodynamic analysis to structural analysis model. Also, as the results of structural behavior evaluation, it was found that the tensile stress on the top slab was maximized at the wave direction of $0^{\circ}$, and tensile stress on the bottom slab was maximized at the wave direction of $45^{\circ}$, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.303-309
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• 2006

Yongdam reservoir located in Jeoliabuk-do has had a lot of concerns for its algal blooming since it has started to fill water. Many water utilities near Yongdam area use reservoirs even though they have some problems with certain algae that cause tastes and odors and clog filters. In this research, dissolved air flotation (DAF) technology was examined for feasibility for removal of algae. OAF can save the capital cost for its compactness, because its hydraulic loadings (overflow rates) are 10 times higher than sedimentation, and hydraulic detention times are much shorter, typically 5 to 15 minutes. As a result of this research, PAC is effective rather than Alum to DAF for pretreatment. Higher DOC plays an important role to change zetapotential negatively to inhibit destabilization of particle to coagulation. The length of pipeline to carry pressurized water into reactor does not affect reaction.

• Journal of Environmental Health Sciences
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• v.24 no.1
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• pp.132-140
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• 1998

Laboratory-scale experiments were conducted using a three-stage rotating biological contactor unit followed by lime precipitation and sedimentation with effluent recycle to the first stage. The purpose of this study was to evaluate the effects of hydraulic loadings of 0.031-0.076 $m^3/m^2/d and recycle ratio of 1 to 3 on the simultaneous removal of organics and nutrients from domestic wastewater. Lime was added to maintain pH of 10.4-11.0 in the coagulation-flocculation reactor. Results showed that the highest nitrogen removal rate of 70.5% occurred at the lower hydraulic loading of 0.031 $m^3/m^2/d at a recirculation rate of 300%, and similarly, highest nitrification occurred at the same hydraulic loading and recycle ratio. Concentration of ammonia nitrogen in the effluent was less than 1 mg/l at the same operating conditions for higher nitrogen removal. Whereas, high BOD and COD removal was observed at hydraulic loading rate of 0.054 $m^3/m^2/d, and high removal of organic matter was evident from the consistent low COD and BOD value. Results obtained from the operating condition of higher loading rate, 300% of recycle rate showed the highest removals. Increasing in recycle rate and hydraulic loading rate increased the volatile solids fraction of the sludges generated to the extent of 47% at 0.076 $m^3/m^2/d hydraulic loading and 300% recirculation rate. Since pH in the flocculator was maintained at the pH of 10.4-11.0, above 90% removal of phosphorus was obtained. Average concentration of suspended solids was always maintained over 40 mg/l in the effluent. Therefore an RBC unit operating at a hydraulic loading near 0.031 $m^3/m^2/d with a recycle rate of 300% is a viable and feasible alternate conditions to produce an effluent with relative low organic matter and phosphorus, provided that there is a neutralization unit to control the pH and SS of the effluent.

• Tunnel and Underground Space
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• v.21 no.1
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• pp.66-81
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• 2011

In this study, it was aimed to develop a thermal-hydraulic-mechanical coupled fracture mechanics code that models a fracture initiation, propagation and failure of underground rock mass due to thermal and hydraulic loadings. The development was based on a 2D FRACOD (Shen & Stephasson, 1993), and newly developed T-M and H-M coupled analysis modules were implemented into it. T-M coupling in FRACOD employed a fictitious heat source and time-marching method, and explicit iteration method was used in H-M coupling. The validity of developed coupled modules was verified by the comparison with the analytical result, and its applicability to the fracture initiation and propagation behavior due to temperature changes and hydraulic fracturing was confirmed by test simulations.

• Environmental Engineering Research
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• v.23 no.2
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• pp.195-204
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• 2018

A pilot scale study was conducted on a down-flow hanging sponge (DHS) reactor installed at a sewage treatment plant in Banda Aceh, Indonesia for treatment of desludging septic tank wastewater. Raw wastewater with an average biochemical oxygen demand (BOD) and total suspended solids of 139 mg/L and 191 mg/L, respectively, was pumped into the reactor. Two different hydraulic retention times (HRTs, 3 h and 4 h) were investigated, equivalent to organic loadings of 1.11 and $0.78kg\;BOD/m^3/d$, respectively. The average BOD concentration in the final effluent was 46 and 26 mg/L at HRTs of 3 and 4 h, respectively. The concentration of retained sludge along the reactor height was 10.2-18.7 g VSS/L-sponge, and the sludge activities were 0.24-0.32 and 0.04-0.40 mg/g VSS/h for heterotrophs and nitrification, respectively. Values of water hold-up volume, dispersion coefficient, and number of tank in-series found from tracer studies of clean sponge and biomass-loaded sponge confirmed that growth of retained sludge on the sponge module improved hydraulic performance of the reactor. Adoption of the DHS reactor by this Indonesian sewage treatment plant would enhance the role of the current desludging septic tank wastewater treatment system.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.789-794
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• 1999

The performance of a small on-site wastewater treatment system consisting of an anaerobic septic tank and upgraded absorbent biofilter was investgted . The anaerobic septic tank was used as a pre-treatment of the absorbent Biofitler instead of the primary clarifier. The treatment capacity of the system was examined by changing the hydraulinc loadings to the Absorbent Biofilter as 2.5㎥/day , 4.5㎥/day, 6.0㎥/day, respective. The effluent from the septic tank was fed into the Absorbent Bilfilter. Based on the experimental results, the quality of treated wastewater satisfied the regulation and the BOD and SS was removed down to approximately 5mg/$\ell$ and 1mg/$\ell$, respectively.

• Korean Journal of Environmental Agriculture
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• v.19 no.2
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• pp.122-127
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• 2000

A stream purification system was applied to the upper reaches of the Masan Reservoir to improve the water quality. This system consisted of two channels which were constructed on both sides of the stream, one side packed with crushed gravels and the other with plastic filter media. The system operated under low pollutant concentrations and high hydraulic loadings during a dry season to avoid clogging of the filter media. Removal rate and efficiency of chemical oxygen demand (COD) in the channel packed with crushed gravel were $14.8g/m^3/d$ and 11.5%, and for the channel with plastic filter media, $50.1g/m^3/d$ and 13.5%, respectively. Removal efficiencies of total phosphorus (T-P) were 6.6% (gravel) and 10.0% (plastic media). These results indicated plastic filter media having relatively high specific surface areas were more efficient than crushed gravels in removing pollutants. However, due to low influent water quality during dry season, the removal efficiencies were low. The proportion of nitrate nitrogen to total nitrogen (T-N) of the inflow was high but, as the system operated under aerobic condition, nitrate nitrogen could not denitrified. Accordingly, total nitrogen was not attenuated with this system. To improve the reservoir water quality effectively, this system should be able to treat the storm runoff containing higher pollutant loadings. When the filter materials are clogged by the storm runoff instead of backwashing, it would be more efficient to replace them, Therefore, the use of natural materials which are light, easily obtaining and replaceable, and have high specific surface areas is recommended.