• 환경위생공학
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• 제13권1호
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• pp.91-103
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• 1998

Design data for COD and nitrogen removal from wastewater were collected from Pilot's Multi-stage Bio-reactor. Hyraulic conditions and pollutant loadings were varied in order to optimize the biological and operational parameters. Pilot's experimental results summarize as followings. 1. T-N removal efficiency in the organic volumetric loading 0.2 kgCOD/m$^{3}$·d was obtained as maxium of 85% at internal recycle ratio 2.5 and in more ratio than this it was decreased. Organic removal efficiency was about 91% under the overall experimental conditions and not influenced by recycle ratio.. 2. Nitrification reaction was shown as maxium in the SCOD$_{cr}$/NH$^{+}$-N ratio of 6.5 and in more ratio than this it was decreased. Denitrification rate was the maxium as 85% in more than 7.5 of SCOD$_{cr}$/NO$_{x}$-N ratio and in the ratio over this ratio it becomes constant. 3. By utilizing an applied new model of Stover-Kincannon from Monod's kinetic model, concentration of T-N in the effluent according to flow quanity in the influent was estimated as 8.74 and -67.5 respectively. The formula for estimating T-N concentration of effluent was obtained like this: N$_e$=N$_0$(1- $\frac{8.74}{(QN$_0$/A)-67.05}$)

• 한국지반환경공학회 논문집
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• 제22권12호
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• pp.41-50
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• 2021

본 연구의 목적은 모래와 타이어칩 혼합토의 반복하중조건 전후 공학적 특성 변화를 파악하는 것이다. 반복하중 시, 시료에 함유된 타이어칩 함량 및 모래와 타이어칩 입자 간의 크기비에 따른 최대전단탄성계수의 변화를 정량화 하고자, 전체 중량 대비 타이어칩 중량을 0, 10, 20, 40, 60, 100%로 하여 시료를 조성하였으며, 타이어칩 평균입경 대비 모래의 평균입경(입자크기비)을 0.44, 1.27, 1.87, 4.00으로 설정하여 혼합토를 조성하였다. 초기 상대밀도 50%의 시료를 floating wall 형태의 몰드에 조성 후, 공기압 축기(air compressor), 압력 패널(pressure panel) 및 뉴메틱 밸브(pneumatic valve)를 이용하여 정하중 재하(=50kPa), 반복하중 재하(=50-150kPa), 정하중 재하(=400kPa) 및 제하 순으로 실험이 이루어 졌다. 위의 실험이 진행됨에 따라 시료의 침하량과 전단파속도를 측정하였다. 시험 결과, 모래-타이어칩 혼합토에 가해지는 반복하중은 시료를 이루는 입자 간 접촉을 타이어칩-타이어칩 또는 타이어칩-모래에서 모래-타이어칩 또는 모래-모래로 전환시켰으며, 이로 인해 타이어칩 함량 40%에서 가장 큰 최대전단탄성계수의 증가를 확인하였다. 또한 입자크기비가 감소함에 따라 동일 타이어칩 함량에서 반복하중 시 최대전단탄성계수 증가량은 증가하였다.

• Earthquakes and Structures
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• 제7권4호
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• pp.463-484
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• 2014

Solid piers with a rounded rectangular cross-section are widely used in railway bridges for high-speed trains in China. Compared to highway bridge piers, these railway bridge piers have a larger crosssection and less steel reinforcement. Existing material models cannot accurately predict the seismic behavior of this kind of railway bridge piers. This is because only a few parameters, such as axial load, longitudinal and transverse reinforcement, are taken into account. To enable a better understanding of the seismic behavior of this type of bridge pier, a simultaneous influence of the various parameters, i.e. ratio of height to thickness, axial load to concrete compressive strength ratio and longitudinal to transverse reinforcements, on the failure characteristics, hysteresis, skeleton curves, and displacement ductility were investigated. In total, nine model piers were tested under cyclic loading. The hysteretic response obtained from the experiments is compared with that obtained from numerical studies using existing material models. The experimental data shows that the hysteresis curves have significantly pinched characteristics that are associated with small longitudinal reinforcement ratios. The displacement ductility reduces with an increase in ratio of axial load to concrete compressive strength and longitudinal reinforcement ratio. The experimental results are largely in agreement with the numerical results obtained using Chang-Mander concrete model.

• 한국물환경학회지
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• 제20권6호
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• pp.603-609
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• 2004

The objective of this study was to determine the optimal operation conditions in an anoxic oxic process to eliminate both organic and nitrogen matters in swine wastewater. For the purpose of this, the removal efficiency was evaluated with various HRTs and internal recycling ratio. During the whole 580 days of experiment, HRTs had been gradually decreased in an order of 20, 14, 12 and l0days, and the internal recycle ratio was kept at 20Q. So as to determine the effect of the internal recycle ratio on the nitrogen removal, the internal recycle ratio had been gradually increased from 20Q to 50Q while HRT was maintained at 12days. As a result, it was shown that the removal efficiency of organic matter was above 95% regardless of changing of HRTs. The average influent concentration of TCODcr and SCODcr were 24,854 mg/L and 18,920 mg/L, respectively. Average removal efficiency of TKN was shown to be nearly 98% when HRT was kept at 12days; however, the $NH_4{^+}-N$ concentration of effluent was shown to be increased when the loading rate of $NH_4{^+}-N$ was increased to $0.602 kgNH_4{^+}-N/m^3$-day by means of decreasing HRT to 10days. It was concluded that nitrogen loading rates should be more considered rather than organic loading rates in case of determining an optimal HRT. When gradually increasing the internal recycle ratio from 20Q to 50Q, the removal efficiency of organic matters and TKN were 96% and 98%, respectively so that no significant changes in removal efficiency was detected. However, when the internal recycle ratio was kept at 50Q, it was revealed that the $NO_3-N$ concentration of effluent seemed to drop and the average $NO_3-N$ concentration of effluent was around 52 mg/L.

• 한국환경과학회지
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• 제5권3호
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• pp.361-367
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• 1996

An inverse fluidized-bed biofilm reactor (IFBBR) was used for the treatment of highly-emulsified oily wastewater. When the concentration of biomass which was cultivated in the synthetic wastewater reached to 6000 mg/1, the oily wastewater was employed to the reactor with a input COD concentration range of 50 mg/1 to 1900 mg/l. Virtually the IFBBR showed a high stability during the long operation period although soma fluctuation was observed. The COD removal efficiency was maintained over 9% under the condition that organic loading rate should be controlled under the value of 1.5 kgCOD/$m^3$/day, and F/M ratio is 1.0 kgCOD/kgVSS/day at $22{\circ}C$ and HRT of 12 hrs. As increasing organic loading rates, the biomass concentration was decreased steadily with decreasing of biofilm dry density rather than biofilm thickness. Based on the experimental jesuits, it was suggested that the decrease in biofilm dry density was caused by a loss of biomass inside the biofilm.

• 한국환경보건학회지
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• 제26권4호
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• pp.15-20
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• 2000

The studies of swine wastewater treatment aim to development of process using soil microorganism. Removal rate of swine wastewater containing organic matter was 99 percent in case of high loading rate. Microorganism was devoted to improve the treatment efficiency of the process. According to the result obtained from biological treatment of high loading rate swine wastewater. Hydraulic retention time was 2.3 days in unit process of biological phosphorus removal. BO $D_{rm}$ / $P_{rm}$ ratio was 1122 in room temperature anaerobic process and 355.6 in mesophilic anaerobic process. And then phosphorus removal rate mesophilic anaerobic process was 3 time as much as than room temperature acaerobic process.

• 한국환경보건학회지
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• 제12권2호
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• pp.27-37
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• 1986

This study was carried out to investigate inflow stream of Chungju intake reservoir and in catchment area, run-off loading amount, distribution of Nitrogen and phosphorus, N/P ratio, correlationship between T-N and chlorophyll a, correlationship between T-P and chlorophyll a, and study of trophic state. Field survey was carried out from June to August, 1985, for the purpose of finding out the nitrogen and phosphorus concentration in Chungju intake reservoir.

• 한국환경보건학회지
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• 제19권3호
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• pp.36-40
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• 1993

The objective of this research was to retrofit an on-site sewage treatment system suitable to current situation of Korea to reduce the pollution loading and preserve the invaluable water resources. Operation at the F/M ratio of 0.1 kg. BOD/kg MLSS day showed 87.1% BOD removal efficiency and 84.5% COD removal efficiency, and its effluent concentration was 6.4 mg/l as BOD and 21.7 mg/l as COD. Average removal of total nitrogen showed high removal efficiency of 80%.

• Environmental Engineering Research
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• 제23권1호
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• pp.70-75
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• 2018

A pilot scale anaerobic fixed-bed with a reactor volume of $2.8m^3$ was built to treat slaughterhouse wastewater. Bamboo rings were chosen as support media mainly because of their cheaper price in underdeveloped countries. Even with their lower porosity and specific surface, the reactor performance showed a maximum 95% COD removal efficiency at an organic loading rate (OLR) of $1kg\;COD/m^3-d$ with its corresponding hydraulic retention time (HRT) of 7.5 d. At a higher OLR of $4.0kg\;COD/m^3-d$, the COD removal efficiency of 75% was achieved with an HRT of 2 d. No big difference in COD removal efficiencies was found between the reactors operated in both upflow and downflow modes. Their operational behavior and effluent characteristics were similar. The effluent COD/TKN ratio of 6.67 at an OLR of $4.0kg\;COD/m^3-d$ was only marginal acceptable range for a subsequent biological denitrification process. Otherwise carbon supplementation is required at a lower OLR.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.896-905
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• 2006

Several soil parameters such as particle characteristics, geological element, drainage and loading conditions are influenced on the shear strength of soil. The characteristics of soil particles are important factor to the shear strength of soil. However, this component is not well considered in the determination of soil strength in Korea. The particle shape of sand was analyzed by utilizing SEM(Scanning Electron Micrograph) and compared its results in terms of aspect ratio, angularity and roughness. Based on the determined soil parameters, the ultimate bearing capacity of sandy ground was estimated by using Terzaghi bearing capacity equation.