• 한국지열·수열에너지학회논문집
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• 제12권3호
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• pp.24-32
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• 2016

Commercial buildings and institutions are generally cooling-dominated and therefore reject more heat to a borehole ground heat exchanger (BHE) than they extract over the annual cycle. Shallow ponds can provide a cost-effective means to balance the thermal loads to the ground and to reduce the length of BHE. This paper presents the analysis results of the impact of design parameters on the length of SWHE pipe and its application effect on geothermal heat pump (GHP) system using BHE. In order to analysis, we applied ${\varepsilon}-NTU$ method on designing the length of SWHE pipe. Analysis results show that the required pipe length of SWHE was decreased with the increase of approach temperature difference and with the decrease of pipe wall thickness. In addition, when the SWHE was applied to the GHP system, the temperature of BHE was more stable than that of standalone BHE system.

• 상하수도학회지
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• 제13권1호
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• pp.43-50
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• 1999

In spite of low energy requirement, and operation and construction cost, biofilters with soil beds have not been operated efficiently. Because of excess moisture in winter and rainy periods, saturated pores in the bed prevent passage and sorption of odorous compounds. Sometimes this results in septic conditions that release previously sorbed and oxidized sulfur. Therefore, an economical and effective alternative needs to be developed. The objectives of this study were to confirm applicability of the granular scrap tires with compost for treating odorous gas as well as to obtain optimum design parameters for proposed system. In lab-scaled test, multiple stage reactors had lower headloss than a single stage reactor and less headloss was occurred for the gas with higher moisture content. For practical purpose, pilot-scaled reactor was operated to remove odor from septic tank, manure and animal wastewater treatment plant and composting machine. According to the results of pilot scaled test, $H_2S$ can be always removed completely and ammonia/amine can be removed excellently when proper moisture content is provided. The results from lab and pilot test showed that granular scrap tire could be replaced with soil as supporting material for biofilter showed excellent drainage because of its ability to reject moisture.

• 상하수도학회지
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• 제32권5호
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• pp.371-379
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• 2018

The lack of seed sludges for Ammonium Oxidizing Bacteria (AOB) and slow-growing ANaerobic AMMonium OXidation (ANAMMOX) bacteria is one of the major problem for large-scale application. In this study, $24m^3$ of single-stage SBR (Sequencing Batch Reactor) was operated to remove nitrogen from reject water using AOB and ANAMMOX bacteria cultivated from activated sludge in the field. The ANAMMOX activity was found after 44 days of cultivation in the ANAMMOX cultivation reactor, and then $0.66kg\;N/m^3/d$ of the nitrogen removal rate was achieved at $0.78kg\;N/m^3/d$ of the nitrogen loading rate at 153 days of cultivation. The AOB cultivation reactor showed $0.2kg\;N/m^3/d$ of nitrite production rate at $0.4kg\;N/m^3/d$ of nitrogen loading rate after 36 days of operation. The cultivated ANAMMOX bacteria and AOB was mixed into the single-stage SBR. The feed distribution was applied to remove total nitrogen stably in the single-stage SBR. The nitrogen removal rate in the single-stage SBR was gradually enhanced with an increase of specific activities of both AOB and ANAMMOX bacteria by showing $0.49kg\;N/m^3/d$ of the nitrogen removal rate at $0.56kg\;N/m^3/d$ of the nitrogen loading rate at 54 days of operation.

• 환경위생공학
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• 제23권4호
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• pp.37-44
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• 2008

In this study we developed the analytical methods for the determination of three neurotoxin; anatoxin-a, saxitoxin and neosaxitoxin using HPLC/FLD system and this analytical methods were applied to real sample; algae culture and algae extracts. For the HPLC/FLD analysis of anatoxin-a samples were concentrated on WCX(Weak Cation Exchanger) SPE and then anatoxin-a in concentrate was derivatized with NBD-F solution. Supernatant was injected on HPLC system. For the HPLC/FLD analysis of saxitoxin and neosaxitoxin samples were separated on the column and then derivatizied by post column reactor for fluorescen detection. For post column reaction of saxitoxin we feed two kinds of reaction solution; Oxidizing Reagent of which composition was periodic acid(7mM) in 50mM potassium phosphate buffer, pH 9 and acidifying reagent of which Composition was 0.5M acetic acid. The LOD value for anatoxin-a, saxitoxin and neosaxitoxin in HPLC/FLD method was 24.3 ng. $35{\mu}g/L$, $27{\mu}g/L$ respectively. We determined the anatoxin-a content of lyophilized anabaena flos-aquae and $20{\mu}g/g$ d.w. of anatoxin-a was detected. We analyzed saxitoxin and neosaxitoxin in algae culture media and extracts of lypopyllized algal cell cultured and that of Deachung reservior. Saxitoxin and neosaxitoxin in real sample were below the limit of detection. Although there are various water treatment processes for removing neurotoxins were suggested no process give simultaneous and complete removal of neurotoxins. It was cocluded that nanofiltration which reject material by size can be a process for removal of neurotoxins.

• 대한기계학회논문집 C: 기술과 교육
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• 제4권1호
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• pp.49-56
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• 2016

본 연구에서는 설계 인자가 지표수 열교환기 길이에 미치는 영향을 분석하였다. 또한 수직 밀폐형 지중열교환기와 지표수 열교환기를 같이 이용한다고 가정한 후, 지중 순환수의 온도 변화를 분석하였다. 지표수 열교환기 출구 온도와 연못 온도의 차이를 크게 하면, 열교환기 파이프 길이는 줄어들었다. 아울러 연못 온도가 높을수록 파이프 길이는 감소하지만, 파이프 바깥지름의 영향은 상대적으로 적었다. 또한 파이프 두께가 얇을수록 전도 열전달에서 열저항의 영향이 감소하기 때문에 파이프 길이는 감소하였다. 수직 밀폐형 시스템에 지표수 열교환기를 추가 적용하면, 지중열교환기 순환수 온도는 시간이 지날수록 감소하였다.

• 상하수도학회지
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• 제28권2호
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• pp.195-206
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• 2014

Immobilization of anaerobic ammonium oxidizing bacteria has been studied to enhance the biomass retention of the slowly growing bacteria and the process stability. The purpose of this study was to compare the nitrogen removal efficiency of granular and immobilized anammox bacteria with poly vinyl alcohol and alginate. The specific anammox activity of the granular, homoginized and immobilized anammox bacteria were $0.016{\pm}0.0002gN/gVSS/d$, $0.011{\pm}0.001gN/gVSS/d$ and $0.007{\pm}0.0005gN/gVSS/d$, respectively. Although the activity decreased to 43.7 % of the original one due to low pH and $O_2$ exposure during the homogination and the immobilization, it was rapidly recovered within 7 days in the following continuous culture. When synthetic T-N concentrations of 100, 200, 400, 800 mg/L were fed, the immobilized anammox bacteria showed higher nitrogen removal efficiencies at all operational conditions than those of granular anammox bacteria. When the sludge retention time was shorten below 30.7 days and the reject water was fed, the nitrite removal efficiency of the granular anammox bacteria dropped to 8 % of the initial value, while that of the immobilized anammox bacteria was maintained over 95 % of the initial one. The immobilization with poly vinyl alcohol and alginate would be a feasible method to improve the performance and stability of the anammox process.

• 멤브레인
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• 제32권2호
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• pp.91-99
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• 2022

모든 인구 계층에 저렴한 비용으로 깨끗한 물의 수요를 충족시키는 것은 해결해야 할 세계적인 문제이다. 막 분리 공정을 통한 해수 및 기수의 탈염은 효율이 높고 확립된 방법이다. 그러나 막 분리 공정은 막 오염, 제거된 오염물의 처리, 그리고 자본집약적 공정이라는 본질적인 문제가 있다. 전기투석은 전위차가 구동력인 막 기반 분리 공정이다. 전기투석막의 장점은 뛰어난 효율과 저렴한 운영 비용이다. 전기투석공정에서 사용되는 이온교환막은 장기간 효율을 잃지 않기 위해 내화학성과 내열성, 그리고 기계적 안정성이 필요하다. 이 때, 전기투석막의 이온교환용량은 이온교환막의 전도도에 따라 크게 달라진다. 본 리뷰에서는 이온 전도도과 안정성을 향상시키기 위한 양이온 교환막과 음이온 교환막의 개조를 중점적으로 논의하였다.

• 한국실내디자인학회논문집
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• 제26권6호
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• pp.210-221
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• 2017

First, we can define how our body perceives the external world and embodies its senses through the philosopher Merleau - Ponty. These philosophical orientations of Merleau-Ponty also appear to urban theorists such as Jane Jacobs, Gordon Cullen, and Juhani Pallasmaa. In other words, after the Second World War, people began to pay attention to human emotions and perceptions while opposing human rational thinking. Especially, they reject the abstract space of modernism and explore the everyday city space where the local character of the area lives. This place is a space where the collective memory of the group is shared over several generations. So, in this space, people's active perceptual system works actively. In the sense of this continuity of time, their ideas intersect with the concept of urban. Specifically, Jacobs criticizes massive development and proposes the development of a small block-based city with a commonality of old and new. In addition, we argue that urban space can be a visually interesting object through the continuous visual concept of urban theorist Cullen. In particular, he rediscovers the value of traditional urban space through visual experience between architecture and urban facilities. Finally, the architectural city theorist, Pallasmaa., criticizes the visual centrality of modern cities and thinks about the value of multidisciplinary space that can be experienced in architecture. This study examines the space of reproduction in detail on the perspective of the body philosophy and urban theorists. In other words, the play space inherits the natural city time, so when our body experiences this play space, we can actively sense and perceive the various senses. So we can invoke the active external actions of our bodies. Through the analysis of the size of the reconstruction space of the architectural city, various types of body senses and responses can be. Yoon Dongju Literary Museum, which renovated the old water tank of the city, can recognize the unfamiliar sense of body in everyday life through the traces and smells of water in the past and the restrained visuality. In addition, Seonyudo Park, which regenerates the waste water purification plant, can experience a phenomenal phenomenon through water space, old concrete and traces of steel. Finally, with the most recently played Seoul Road 7017 can experience interesting urban spaces in terms of a variety of plants, a human scale space creating movement, and a continuous visual.

• Membrane and Water Treatment
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• 제11권4호
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• pp.303-312
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• 2020

This study aims to investigate at a laboratory scale fluorides removal from an industrial wastewater having excessive F^- concentration through a hybrid process combining neutralization and membrane separation. For the membrane separation operation, both Reverse Osmosis (RO) and Nanofiltration (NF) were investigated and confronted. The optimized neutralization step with hydrated lime allowed reaching fluoride removal rates of 99.1± 0.4 %. To simulate continuous process, consecutive batch treatments with full recirculation of membrane process brines were conducted. Despite the relatively high super saturations with respect to CaF₂, no membrane cloaking was observed. The RO polishing treatment allowed decreasing the permeate fluoride concentration to 0.9± 0.3 mg/L with a fluoride rejection rate of 93± 2% at the optimal transmembrane pressure of around 100 psi. When NF membrane was used to treat neutralization filtrate, the permeate fluoride concentration dropped to 1.1± 0.4 mg/L with a fluoride rejection rate of 88± 5% at the optimal pressure of around 80 psi. Thus, with respect to RO, NF allowed roughly 20% decrease of the driving pressure at the expense of only 5% drop of rejection rate. Both NF and RO permeates at optimal operating transmembrane pressures respect environmental regulations for reject streams discharge into the environment.

• Computers and Concrete
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• 제27권4호
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• pp.333-341
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• 2021

Steel slag, an industrial reject from the steel rolling process, has been identified as one of the suitable, environmentally friendly materials for concrete production. Given that the coarse aggregate portion represents about 70% of concrete constituents, other economic approaches have been found in the use of alternative materials such as steel slag in concrete. Unfortunately, a standard framework for its application is still lacking. Therefore, this study proposed functional model equations for the determination of strength properties (compression and splitting tensile) of steel slag aggregate concrete (SSAC), using gene expression programming (GEP). The study, in the experimental phase, utilized steel slag as a partial replacement of crushed rock, in steps 20%, 40%, 60%, 80%, and 100%, respectively. The predictor variables included in the analysis were cement, sand, granite, steel slag, water/cement ratio, and curing regime (age). For the model development, 60-75% of the dataset was used as the training set, while the remaining data was used for testing the model. Empirical results illustrate that steel aggregate could be used up to 100% replacement of conventional aggregate, while also yielding comparable results as the latter. The GEP-based functional relations were tested statistically. The minimum absolute percentage error (MAPE), and root mean square error (RMSE) for compressive strength are 6.9 and 1.4, and 12.52 and 0.91 for the train and test datasets, respectively. With the consistency of both the training and testing datasets, the model has shown a strong capacity to predict the strength properties of SSAC. The results showed that the proposed model equations are reliably suitable for estimating SSAC strength properties. The GEP-based formula is relatively simple and useful for pre-design applications.