• 상하수도학회지
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• 제24권1호
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• pp.5-14
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• 2010

A pilot-scale biological aerated filter (BAF) was operated with an anaerobic, anoxic and oxic zone at $23{\pm}1^{\circ}C$. The influent sCOD and total nitrogen concentrations in the feedwater were approximately 250 mg/L and 35 mg N/L, respectively. sCOD removal at optimum hydraulic retention time (HRT) of 3 hours with recirculation rates of 100, 200 and 300% in the column was more than 96%. Total nitrogen removal was consistently above 80% for 4 and 6 hours HRT at 300% recirculation. For 3 hours HRT and 300% recirculation, total nitrogen removal was approximately 79%. Based on fitting results, the kinetic parameter values on nitrification and denitrification show that as recirculation rates increased, the rate of ammonia and nitrate transformation increased. The ammonium loading rates for maximum ammonium removed were 0.15 and 0.19 kg $NH_3$-N/$m^3$-day for 100% and 200% recirculation, respectively. The experimental results demonstrated that the BAF can be operated at an HRT of 3 hours with 200 - 300% recirculation rates with more than 96 % removal of sCOD and ammonium, and at least 75% removal of total nitrogen.

• 청정기술
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• 제19권3호
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• pp.295-299
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• 2013

미국 환경 보호청(Environmental Protection Agency, EPA)의 생물저류 설계기준에 근거한 비점오염원 처리시설의 제거효율 및 성능을 분석하고자 기본 모형 실험장치(basic column reactor, BCR)와 파일럿 규모의 식생 실험 장치를 대상으로 각각 수행하였다. BCR을 이용하여 초기강우 유출수의 유입속도(유량), 식재 층의 조성 및 구성 비율, 등 처리시설의 설계에 필요한 적정인자 값을 도출하였으며 이를 식생 실험 장치에 적용하여 비점오염원의 제거 효율을 분석하였다. 비점오염원으로는 합성된 강우(synthetic rainfall)와 실제 현장(도로변과 주차장)에서 채수한 초기강우 유출수(first rainfall runoff)를 각각 사용하였다. 부유물질(Suspended Solid, SS), 생물학적 산소 요구량(Biochemical oxygen demand, BOD), 화학적 산소요구량(Chemical Oxygen Demand, COD), 총질소(Total Nitrogen, T-N), 총인(Total Phosphorus, T-P) 분석항목 모두 80% 이상을 상회하는 제거효율을 보이고 있음을 확인하였다.

• Advances in nano research
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• 제10권1호
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• pp.77-90
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• 2021

In the present study, novel chitosan coated magnetic magnetite (Fe3O4) nanoparticles were successfully biosynthesized from mushroom, Agaricus campestris, extract. The obtained bio-nanocomposite material was used to investigate ultra-fast and highly efficient for removal of Ni2+ ions in a fixed-bed column. Chitosan was treated as polyelectrolyte complex with Fe3O4 nanoparticles and a Fungal Bio-Nanocomposite Material (FBNM) was derived. The FBNM was characterized by using X-Ray Diffractometer (XRD), Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Fourier Transform Infrared spectra (FTIR) and Thermogravimetric Analysis (TGA) techniques and under varied experimental conditions. The influence of some important operating conditions including pH, flow rate and initial Ni2+ concentration on the uptake of Ni2+ solution was also optimized using a synthetic water sample. A Central Composite Design (CCD) combined with Response Surface Modeling (RSM) was carried out to maximize Ni2+ removal using FBNM for adsorption process. A regression model was derived using CCD to predict the responses and analysis of variance (ANOVA) and lack of fit test was used to check model adequacy. It was observed that the quadratic model, which was controlled and proposed, was originated from experimental design data. The FBNM maximum adsorption capacity was determined as 59.8 mg g-1. Finally, developed method was applied to soft drinks to determine Ni2+ levels. Reusability of FBNM was tested, and the adsorption and desorption capacities were not affected after eight cycles. The paper suggests that the FBNM is a promising recyclable nanoadsorbent for the removal of Ni2+ from various soft drinks.

• KSBB Journal
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• 제25권5호
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• pp.421-428
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• 2010

본 논문은 복합흡수제를 이용하여 유해가스를 처리하기 위해 식물정유의 주요구성성분을 파악한 식물정유로 황화수소가스의 처리효율을 규명하고자 하였다. 또한 복합흡수제와 황화수소가스에 의한 제거반응을 위한 적정조건을 분석하였으며 그 결과는 아래와 같이 요약 할 수 있다. 1) 황화수소가스는 중화반응으로 처리하고 져 할 경우, 식물정유의 화학구조에서 알코올기, 알데히드기, 에스터기 등이 중화반응에 관여한다. 실험결과 앞서 언급한 화학작용기가 포함되어 있는 경우에 아민계열의 2-아미노에탄올 및 식물정유의 복합흡수제와 황화수소 가스와의 중화반응으로 염을 형성하여 유해가스 제거효율이 98%에 도달한다. 2) 황화수소가스를 제거하는 중화반응의 경우에 온도와 pH에 따라 처리효율이 크게 달라졌다. 높은 온도보다는 낮은 온도에서 제거효율이 거의 98%이상 나타났다. 적정 pH는 중성영역에서 비교적 처리효율을 확인하였다. 3) 황화수소가스의 처리효율은 초기농도에 따라 처리효율이 크게 차이가 나타났다. 황화수소의 초기농도가 1,100 ppm 이상인 경우에 처리효율은 40%로 나타났다. 반면, 240 ppm 이상인 경우에는 10분이내에 황화수소 가스 처리 효율이 90%이상 처리되는 것으로 나타났다.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2004년도 춘계학술발표회
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• pp.81-84
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• 2004

Control of Sediment is very important in prawn farm due to the eruption of toxic material such as W1ionized H2S, NH3 and NO2-. In this study, column test study, column with filter media such as activated carbon, zeolite, oyster shell and iron chloride to evaluate the reduction of toxicity from sediment ammonia-N(NH3) was effectively removed by Zeolite and oyster shell. It was indicated that ammonium ion(NH4+) was removed by ion exchange of zeolite. And the ammonia in the column of oyster shell was existed as the form of NH4+, which is not toxic for prawn because oyster shell was stably kept around pH 8. Therefore, some of ammonia(NH3) was reduced by oyster shell. Hydrogen sulfide and COD were effectively removed by adsorption of activated carbon and a partial removal of hydrogen sulfide was accomplished by Oyster shell. Phosphorous was removed by activated carbon, oyster shell and iron chloride. In prawn farm, the concentration of ammonia was increased with increase of pH by algae photosynthesis in the column of activated carbon, zeolite and iron chloride, but it was revealed that pH was stably kept in the column of oyster shell.

• Steel and Composite Structures
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• 제36권4호
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• pp.427-446
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• 2020

This paper carries out the progressive collapse analysis of stainless steel composite beam-to-column joint sub-models and moment-resisting frames under column removal scenarios. The static flexural response of composite joint sub-models with damaged columns was initially explored via finite element methods, which was validated by independent experimental results and discussed in terms of moment-rotation relationships, plastic hinge behaviour and catenary actions. Simplified finite element methods were then proposed and applied to the frame analysis which aimed to elaborate the progressive collapse response at the frame level. Nonlinear static and dynamic analysis were employed to evaluate the dynamic increase factor (DIF) for stainless steel composite frames. The results suggest that the catenary action effect plays an important role in preventing the damaged structure from dramatic collapse. The beam-to-column joints could be critical components that influence the capacity of composite frames and dominate the determination of dynamic increase factor. The current design guidance is non-conservative to provide proper DIF for stainless steel composite frames, and thus new DIF curves are expected to be proposed.

• Environmental Engineering Research
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• 제19권1호
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• pp.107-113
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• 2014

Small sized manganese dioxide particles are immobilized onto the surface of sand by the wet impregnation process. The surface morphology of the solid, i.e., immobilized manganese dioxide natural sand (IMNS) is performed by taking scanning electron microscope images and characterized by the X-ray diffraction data. The specific surface area of the solid is obtained, which shows a significant increase in the specific surface area obtained by the immobilization of manganese dioxide. The $pH_{PZC}$ (point of zero charge) is found to be 6.28. Further, the IMNS is assessed in the removal of As(III) and As(V) pollutants from aqueous solutions under the batch and column operations. Batch reactor experiments are conducted for various physicochemical parametric studies, viz. the effect of sorptive pH (pH 2.0-10.0), concentration (1.0-25.0 mg/L), and background electrolyte concentrations (0.0001-0.1 mol/L $NaNO_3$). Further, column experiments are conducted to obtain the efficiency of IMNS under dynamic conditions. The breakthrough data obtained by the column experiments are employed in non-linear fitting to the Thomas equation, so as to estimate the loading capacity of the column for As(III) and As(V).

• 자원리싸이클링
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• 제24권6호
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• pp.69-77
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• 2015

광미의 처리를 위한 heap bioleaching은 유망 기술이나 이 과정을 오랜 기간 수행한 연구는 부족한 상황이다. 본 연구는 약 436일 동안의 column bioleaching실험을 통해, 광미에서 고농도 비소의 제거특성을 평가하였다. 높이 350 mm의 플라스틱 column에 750 g의 광미와 A. thiooxidans 및 A. ferrooxidans로 구성된 호산성 박테리아를 접종하여 실험을 진행하였다. 비소제거 효율을 확인하고, 그 관련 기작을 이해하고자 침출액의 산화 환원전위와 pH, 액중 철 이온(ferrous와 ferric)의 생성 및 비소 농도를 측정하였다. 실험 436일 후, 비소의 제거율을 약 70%까지 달성 할 수 있었다. 하지만, 부분적으로 침출율이 감소하는 경향을 확인할 수 있었고, 이는 비소의 독성으로 인한 박테리아 군집의 활성도 저하에 의한 것으로 판단되었다. 본 연구의 결과는 향후 광미의 heap bioleaching 연구를 위한 기초 자료로서 활용될 수 있을 것으로 기대된다.

• Journal of Microbiology and Biotechnology
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• 제5권1호
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• pp.41-47
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• 1995

Biodegradation of toluene in liquid effluent stream was carried out using biofilms of Pseudomonas putida formed on celite particles in the bubble column bioreactor. Silicon rubber tubing was installed at the bottom of the bioreactor and liquid toluene was circulated within the tubing. Toluene diffused out of the tube wall and was transferred into the culture broth where degradation by biofilms occurred. The operating variables affecting the formation of biofihns on celite particles were investigated in the bubble column bioreactor, and it was found that formation of bifilm is favored by high dilution rate and supply rate of carbon source which stimulate the growth of initially attached cells. Continuous biodegradation of toluene using biofilms was stablely conducted in the bioreactor for more than one month without any significant fluctuation, showing a removal efficiency higher than 95% at the toluene transfer rate of 1.2 g/L/h.

• Computers and Concrete
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• 제12권3호
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• pp.351-375
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• 2013

Post-punching resistance of a flat slab can help redistribute the gravity loads and resist progressive collapse of a structure following initial damage. One important difficulty with accounting for the post-punching strength of a slab is the discontinuity that develops following punching shear. A numerical simulation technique is proposed here to model and evaluate post-punching resistance of flat slabs. It is demonstrated that the simulation results of punching shear and post-punching response of the model of a slab on a single column are in good agreement with corresponding experimental data. It is also shown that progressive collapse due to a column removal (explosion) can lead to punching failure over an adjacent column. Such failure can propagate throughout the structure leading to the progressive collapse of the structure. Through post-punching modeling of the slab and accounting for the associated discontinuity, it is also demonstrated that the presence of an adequate amount of integrity reinforcement can provide an alternative load path and help resist progressive collapse.