Wastewater management is increasingly emphasizing economic and environmental sustainability. Traditional methods in sewage treatment plants have significant implications for the environment and the economy due to power and chemical consumption, and sludge generation. To address these challenges, a study was conducted to develop the Intermittent Cycle Extended Aeration System (ICEAS). This approach was implemented as the primary technique in a full-scale wastewater treatment facility, utilizing key operational factors within the standard Sequencing Batch Reactor (SBR) process. The optimal operational approach, identified in this study, was put into practice at the research facility from January 2020 to December 2022. By implementing management strategies within the biological reactor, it was shown that maintaining and reducing chemical quantities, sludge generation, power consumption, and related costs could yield economic benefits. Moreover, adapting operations to influent characteristics and seasonal conditions allowed for efficient blower operation, reducing unnecessary electricity consumption and ensuring proper dissolved oxygen levels. Despite annual increases in influent flow rate and concentration, this study demonstrated the ability to maintain and reduce sludge production, electricity consumption, and chemical usage. Additionally, systematic responses to emergencies and abnormal situations significantly contributed to economic, technical, and environmental benefits.

Membrane bioreactor (MBR) provides the benefits on high effluent quality and construction cost without the secondary clarification. Despite of these advantages, fouling, which clogs the pore in membrane modules, affects the membrane life span and effluent quality. Studies on the laboratory scale MBR were focused on the control of particulate fouling, organic fouling and inorganic fouling. However, less studies were focused on the control of biofouling and microbial aspect of membrane. In the full scale operation, most MBR produces high effluent quality to meet the national permit of discharge regulation. In this study, the performance and microbial community analysis were investigated in two MBRs. As the results, the performance of organic removal, nitrogen removal, and phosphorus removal was similar both MBRs. Microbial community analysis, however, showed that Azonexus sp. and Propionivibrio sp. contributed to indirect fouling to cause the chemical cleaning in the DX MBR.

Complaints about foul odors are emerging as an issue, and the number of complaints is steadily increasing every year. Biofiltration is known to remove harmful or odorous substances from the atmosphere by using microorganisms, and full-scale biofilters are being installed and operated in various environmental and industrial facilities. In this study, the current status and actual odor removal efficiency of full-scale biofilters installed in publicly owned treatment facilities such as sewage, manure, and livestock manure treatment plants were investigated. In addition, the effects of design and operating factors on their efficiency were also examined. As a result, it was found that odor prevention facilities with less than 30% odor removal efficiency based on complex odors accounted for 40%-50% of the biofilters investigated. In investigating the appropriate level of operating factors on odor removal efficiency, it was found that compliance with the recommended values p lays a significant role in improving odor removal efficiency. In the canonical correlation analysis for the on-site biofilter operation and design data, residence time and humidity were found to be the most critical factors. The on-site biofilter operation and design data were analyzed through canonical correlation analysis, and the residence time and humidity maintenance were found to be the most important factors in the design and operations of the biofilter. Based on these results, it is necessary to improve the odor removal efficiency of on-site biofilters by reviewing the effectiveness of the operation factors, improving devices, and adjusting operating methods.

In high-level radioactive waste disposal, a high temperature is generated from the canister containing the waste in the engineered barrier, while groundwater flows into the buffer system from the host rock. The temperature increase and groundwater inflow result in the water phase change and saturation variation. Saturation change is related to the thermal conductivity of buffer material; hence the phase change and saturation strongly interact with the temperature evolution. The complex coupled behavior affects the stability of the whole disposal system, and the security of the repository is critical to human-being life. However, it is difficult to predict the long-term coupled behavior in the disposal system due to the considerable field-test scale, and therefore a numerical simulation is a suitable method having repeatability and cost-effectiveness. DECOVALEX is an international cooperating project for developing numerical methods and models for thermo-hydro-mechanical-chemical (THMC) interaction. DECOVALEX has a four-year cycle with various topics. At the current phase, Task C aims to simulate the full-scale emplacement (FE) experiment performed at Mont Terri underground rock laboratory. Nine research groups are participating in the task, and among them, KAERI simulates the experiment using OGS-FLAC. The simulator combines OpenGeoSys for TH simulation and FLAC3D for M simulation. Through the benchmark simulation, we verified OGS-FLAC for the two-phase flow analysis in the disposal system and finally modeled the FE experiment with a three-dimensional grid. We performed a simple sensitivity analysis to investigate the effect of input parameters on the two-phase flow system and confirmed that the compressibility and permeability affected the flow behavior. We also compared the simulation results to the field data and obtained well-matched results from a series of simulation.

The frequent detection and occurrence of micropollutants (MPs) in aquatic ecosystems has raised public health concerns worldwide. In this study, the behavior of 50 MPs was investigated in three different domestic wastewater treatment plants (WWTPs). Furthermore, the Kruskal-Wallis test was used to assess the geographical and seasonal variation of MPs in the WWTPs. The results showed that the concentrations of 43 MPs ranged from less than 0.1 to 237.6 μg L-1, while other seven MPs including 17-ethynylestradiol, 17-estradiol, sulfathiazole, sulfamethazine, clofibric acid, simvastatin, and lovastatin were not detected in all WWTPs. Among the detected MPs, the pharmaceuticals such as metformin, acetaminophen, naproxen, and caffeine were prominent with maximum concentrations of 133.4, 237.6, 71.5, and 107.7 μg L-1, respectively. Most perfluorinated compounds and nitrosamines were found at trace levels of 1.2 to 55.3 ng L-1, while the concentration of corrosion inhibitors, preservatives (parabens), and endocrine disruptors ranged from less than 0.1 to 4310.8 ng L-1. Regardless of the type of biological treatment process such as MLE, A2O, and MBR, the majority of pharmaceuticals (except lincomycin, diclofenac, iopromide, and carbamazepine), parabens (except Methyl paraben), and endocrine disruptors were removed by more than 80%. However, the removal efficiencies of certain MPs such as atrazine, DEET, perfluorinated compounds (except PFHxA), nitrosamines, and corrosion inhibitors were relatively low or their concentration even increased after treatment. The results of statistical analysis reveal that there is no significant geographical difference in the removal efficacy of MPs, but there are temporal seasonal variations in all WWTPs.

In this study, we learned about the effects of indoor radon concentration reduction associated with the operation of a mechanical ventilation system at an apartment house. The experimental parameters were mainly the indoor radon level and air change rate, which were controlled by the amount of emissions released and fan motor speed. Even at the high level of radon diffused in an apartment house, indoor radon concentrations converged to the Korean national guideline level within 3 to 4 hours when the air was ventilated at 0.5 ACH and 0.7 ACH. In the case of 0.3 ACH, however, where the degree of ventilation was insufficient compared to the legal air change rate, the high concentration indoor radon could not be sufficiently removed even if the mechanical ventilation system was operated for more than 14 hours continuously. When the indoor radon level was high, the reduction rate was 34.3% for 0.3 ACH, 70.4% for 0.5 ACH, and 69.7% for 0.7 ACH at 6 hours-operation, while at the medium-level, indoor radon can be reduced by 46.2% (0.3 ACH) to 73.2% (0.7 ACH). Depending on the indoor concentration range, it may be required to secure a ventilation rate of 0.5 ACH or more at all times. In addition, in apartment houses with excellent airtight performance, even if indoor radon is at a level similar to the national guideline, it is difficult to expect a reduction in the concentration due to natural decay. Therefore, it is desirable to lower the indoor concentrations as much as possible.

In this study, the removal performance of high-concentration H2S and complex odors was evaluated for bio-filters installed in sewage treatment plants and manure treatment plants. The amount of odor generation according to temperature was found to be higher in summer than in spring. It was found that the longer the empty bed retention time of the bio-filter, the higher the odor removal efficiency. Therefore, in order to effectively remove odors, it is necessary to maintain a sufficiently long residence time when designing a bio-filter. In addition, a case in which a bio-filter and a wet pre-treatment system were combined to remove high-concentration odors was studied. The result showed that the wet pre-treatment was effective in removing high-concentration odors. In particular, most of the hydrogen sulfide could be adequately removed by wet pre-treatment.

본 연구에서는 원예특작시설 내재해형 규격서에 등록되어 있는 폭이 넓은 단동온실(10-단동-5형)을 대상으로 기초의 경계조건과 서까래 강관의 이음 유무에 대해 실물 크기 실험을 실시하고 그 결과를 수치해석 결과와 비교하여 이음부가 있을 때 구조성능 차이에 대해 알아보았다. 각 측정 위치별 변위를 실험에서 측정한 값과 수치해석으로 예측한 값을 비교한 결과에서는 기초의 조건 및 서까래 강관 이음 유무에 상관없이 모두 상당한 차이를 보였고, 힌지 조건 보다 고정 조건이 상대적으로 차이가 컸다. 그리고 모든 절점을 강접합으로 가정하고 구조해석한 결과를 구조실험과 비교한 결과에서는 힌지조건이 고정조건 보다 잘 일치하였지만 해석값이 실험값 보다 크게 나타났다. 수치해석은 모든 절점을 강접합으로 가정했기 때문에 실제 성능과 달랐다. 따라서 현재 모든 절점을 강접합 으로 가정하고 온실을 설계를 하면 과소설계될 우려가 있어 앞으로 신뢰성 높은 온실 설계를 위해서는 서까래와 도리가 교차하는 교차부 성능 특성을 고려한 구조해석 기술 개발이 이루어져야 할 것으로 판단된다.

본 연구에서는 Froude 수 1.0, 길이 약 10 m 급 소형 고속선의 저항성능과 승선감을 향상시키기 위해 선미 끝단에 트림 탭을 부착하여 항주자세를 제어하였고, 트림 탭의 제원에 따른 성능을 확인하기 위해 CFD 해석을 수행하였다. 먼저 선행 연구로부터 수치 해석이 수행되는 스케일에 따라 결과에 차이가 있는 것이 확인되었고, 이를 피하고자 실선 스케일에서의 해석을 수행하였다. 부착된 트림 탭의 코드 길이는 LPP의 0.5, 1.0, 1.5 %였으며, 선저 면과의 각도는 5 간격으로 변화를 주었다. 트림 탭은 선박의 선미트림과 부상량을 감소시키는 효과가 있었으며, 이 효과는 트림 탭의 선저 면과의 각도가 클수록, 코드 길이가 길수록 증가하였다. 이로 인해 압력 저항은 감소하고 전단저항은 증가하였으며, 두 성분의 변화량에 따라 전 저항 저감율이 결정되었다. 결과로부터 대상 선박의 최적 항 주자세는 약 1.5 의 선미트림으로 특정되었고, 이때 저항성능은 약 27 % 개선되었다.

PURPOSES : The objective of this study is to analyze the uniform diffusion mechanism of precursor gas species, and the effect of NOx reduction technology in a full-scale particulate matter testing facility, using computational fluid dynamics (CFD). METHODS : A full-scale environment chamber was constructed to evaluate the effects of particulate matter reduction technologies on the road. CFD analysis was conducted to simulate the road environment conditions in the chamber, and investigate the effect of the NOx removal panel. The time required to reach the NOx concentration to target value in the fluid field was determined at a given inflow velocity, inlet direction, and initial inflow concentration. The effect of the NOx removal panel, and solar energy on the reduction characteristics of the NOx concentration in the environment chamber was analyzed. RESULTS : The inflow velocity was determined to be the major factor affecting the time required to reach a uniform target NOx concentration in the environment chamber. The inlet location in the transverse direction requires additional time to approach the uniform target concentration, than the longitudinal direction at the same inflow velocity. Based on the CFD analysis in the 1ppm concentration condition of the chamber, a two-fold increase in the NOx removal panel efficiency can reduce the time to target concentration by approximately 50%. It is also observed that a 20% increase in solar energy can decrease the time to target concentration by 4%–12% depending on the panel efficiency. CONCLUSIONS : This study proved that a full-scale environment chamber can be effectively utilized to evaluate the particulate matter reduction technologies applied in road facilities

최근 국내 지진 발생 빈도 및 강도가 증가함에 따라 지진 발생시 건물 주요 구조부에 대해서는 내진설계 및 내진 구조기술이 적용되어 지진에 대비하고 있으나, 비구조 요소인 커튼월과 창호에 대해서는 내진에 대비한 충분한 고려가 이루어지지 못하고 있다. 본 연구에서는 동적 내진성능 기준을 만족할 수 있는 커튼월을 개발하기 위해 동적 지진파 인가 시 커튼월이 파손 없이 대응 가능한 지진 변위 대응 패스너를 적용하여 동적 내진성능실험을 통해 이를 규명하고자 한다. 동적 내진성능실험을 수행한 결과, 본 연구에서 제시한 3축 이동형 패스너를 활용한 커튼월이 실제 지진파에 대응 가능하다는 것을 확인할 수 있었다.

최근 건설기술발전은 시공순서 세분화와 단면강성증진과 같은 기술변화로 선형조건 및 시공여건에 따라 요구되고 있는 다양한 교량 상부거더 형식이 개발되고 있다. 즉, 교량하부 형하공간이 부족한 곳에 설치하여야 하는 저형고 또는 장경간 거더와 같이 각각의 교량 설치 위치 상황에 따라 다른 형식을 요구되고 있다. 이러한 요구로 기존의 하로판형교를 개선한 아치 엣지보로 보강된 U형 강합성 교량을 연구대상 교량으로 선정하게 되었다. 따라서 본 연구는 아치 형태로 변화는 I형 강재의 상부 압축부에 고강도 콘크리트를 충전시켜 각각의 주거더를 구성시킨 하로교형식의 강합성 U형거더를 실물제작하여 구조거동을 분석하였다. 실험하중은 2단계로 구분하여 적용하였다. 1단계는 설계하중 1,200kN의 2.5배인 1차 실험하중 3,000kN을 재하하여 실험오차와 재료비선형성을 확인하였다. 2단계 실험하중 2,000kN에서는 선형분포를 나타냈고 하중제거상태에서 잔류변형이 발생하지 않았다. 분석결과, 아치단면으로 변하는 주거더와 주거더 상단의 충전콘크리트의 합성은 단부의 압축력 집중현상과 같은 아칭효과를 나타냈다.

This study was performed to assess particulate matter removal efficiency of domestic air cleaner products in a field condition. The assessment also included air cleaners with different air removal mechanisms. The particulate matter (PM2.5) removal test with a different air removal mechanism using air cleaners showed that the electrostatic precipitation technique showed better performance compared with HEPA filters and other types of systems. Its removal efficiency was almost 95% in one of our operation times in the given test condition. It was assumed that not only the type of removal system but also the individual design, supply and exhaust system, and the automatically controlled air volume are involved in the removal efficiency. With respect to the area of application, tests with air cleaners for 40 m2, 60 m2, and 80 m2 areas revealed that particulate matter removal efficiency increased with the air cleaner that had a broad area of application. However, particulate matter removal efficiency by air cleaners did not correspondingly increase with the increase of the area of application. Moreover, the installation location did not influence particulate matter removal efficiency. Our results are expected to be used as the basic information for indoor air quality improvement and prediction using air cleaners.

Existing reinforced concrete frame buildings designed for only gravity loads have been seismically vulnerable due to their inadequate column detailing. The seismic vulnerabilities can be mitigated by the application of a column retrofit technique, which combines high-strength near surface mounted bars with a fiber reinforced polymer wrapping system. This study presents the full-scale shaker testing of a non-ductile frame structure retrofitted using the combined retrofit system. The full-scale dynamic testing was performed to measure realistic dynamic responses and to investigate the effectiveness of the retrofit system through the comparison of the measured responses between as-built and retrofitted test frames. Experimental results demonstrated that the retrofit system reduced the dynamic responses without any significant damage on the columns because it improved flexural, shear and lap-splice resisting capacities. In addition, the retrofit system contributed to changing a damage mechanism from a soft-story mechanism (column-sidesway mechanism) to a mixed-damage mechanism, which was commonly found in reinforced concrete buildings with strong-column weak-beam system.