• 상하수도학회지
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• 제18권2호
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• pp.228-234
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• 2004

Dissolved air flotation (DAF), in which suspended solids are removed from water by means of micro-size air bubbles raising slowly up in water and lifting solids from water (smaller than those) attached onto the micro-bubbles as well as those (larger than solids) being attached on these, have been used in water and wastewater since 1920s. The dissolved air flotation technology was originally based on the laminar flow conditions prevailing in water to be treated, but the latest development in that technology has led now to a situation, in which the flow conditions may also be turbulent ones in the modem dissolved air flotation units. Despite of that, the flotation phenomenon used in this unit operation for removal suspended solids from water or wastewater is still the same.

• 대한환경공학회지
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• 제33권10호
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• pp.739-747
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• 2011

충청남도 주요 지류하천 유역을 정확히 파악하고 수질개선이 우선적으로 필요한 하천유역을 선정하기 위해 충청남도 주요 지류하천 81개를 대상으로 유량 및 수질을 모니터링 하였다. 충청남도의 남부와 북부지역에 위치한 지류하천들의 유량이 상대적으로 많은 것으로 나타났으며, 금강수계 논산천 유역의 하천들과 삽교호수계의 곡교천, 무한천, 삽교천 등이 큰 경향을 보였다. 수질항목에 관계없이 유역면적에 비해 오염원이 밀집되어 있는 금강수계의 논산천 유역, 삽교호수계의 곡교천 유역, 안성천 유역에 위치한 하천들이 수질오염물질의 농도는 높은 것으로 나타났다. 한편, '환경정책기본법'의 하천수질 II등급을 금강수계의 하천들은 64%, 삽교호수계의 하천들은 45%, 서해수계의 하천들은 26% 만족한 반면, 안성천수계의 하천들은 모두 하천수질 II등급을 초과하여 충청남도에서는 안성천수계, 서해수계, 삽교호수계 순으로 하천 수질개선을 위한 정책을 수립하여야 한다. 결론적으로 충청남도에서 수질개선이 필요한 하천유역은 하천 유량이 많고 수질오염물질의 농도가 높은 강경천, 금천, 논산천, 석성천, 승천천, 정안천, 증산천(이상 금강수계), 곡교천, 남원천, 매곡천, 무한천, 삽교천, 온천천, 천안천(이상 삽교호수계), 광천천, 당진천, 대천천, 도당천, 와룡천, 청지천, 판교천, 흥인천(이상 서해수계), 둔포천, 성환천, 입장천(이상 안성천수계) 등이며, 이러한 하천유역에는 하천의 수질개선을 위해 유역 내 오염원 저감을 위한 환경기초시설의 설치 등과 같은 수질개선방안의 수립 및 시행이 시급한 것으로 판단된다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권3호
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• pp.275-284
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• 1998

Standard on the carbon dioxide extinguishing system was prepared by the committed of the national fire protection assocition(NFPA)in USA on 1980. And this code is also applied to the design of a marine fire extinguishing system The most important problem in design is the uniform discharge of $CO_2$ through each nozzle from the high pressure $CO_2$ storage facility. The purpose of this paper is to develop the computer software to design the marine fire protection piping system. By solving the continuity equation energy equation and Bernoulli's equation simulataneously the flowrate in branch pipelines and discharge nozzles can be calculated.

• 한국가시화정보학회지
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• 제16권1호
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• pp.54-60
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• 2018

It is important to develop more efficient and productive casting processes for an automated high precision molten-metal casting system. Detailed analysis of molten-metal flow in the casting process by the numerical approach will help to optimize the control of a ladle. In this study, the smoothed particle hydrodynamics method was applied to analyze casting flow characteristics with different tilting angular speed and initial molten-metal level. The smoothed particle hydrodynamics technique has advantages to easily handle non-linear free surface behavior with the absence of a computational mesh. We found that tilting angular speed has relatively greater effect on the casting flowrate and that the effect of the initial molten-metal level is only minor. Further extensive study will be necessary to find an optimal condition for high efficient casting system.

• 대한환경공학회지
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• 제38권9호
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• pp.476-481
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• 2016

압력지연삼투는 삼투압을 구동력으로 하여 에너지를 생산하는 새로운 막 기술이다. 압력지연삼투는 반투과성 막을 사이에 두고 삼투압으로 인해 저농도의 유입원수가 고농도의 유도용액으로 이동하는 것이다. 본 연구는 역삼투 공정의 농축수를 유도용액으로, 역삼투 공정의 생산수를 유입원수로 하여 8인치 나권형 막모듈의 성능을 평가 하였다. 실험에 사용된 유입원수와 유도용액의 유량은 2.4 L/min, 5.0 L/min, 10.0 L/min, 압력범위는 5 bar에서 30 bar이다. 유입원수와 유도용액의 농도, 유입유량, 유입비에 따른 공정 성능의 영향을 본 연구에서 확인 하였다. 중요 결과로 유도용액의 농도의 증가는 압력지연삼투 공정의 전력밀도, 투과수량을 향상시키는 결과를 보였다. 유입유량의 증가 또한 전력밀도와 투과수량을 향상시키는 결과를 보였다. 또한 최대 전력밀도를 형성하는 유입원수와 유도용액의 최적 유입비는 1:1의 비에서 나타났다.

• 한국물환경학회지
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• 제26권5호
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• pp.860-870
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• 2010

Long term monthly monitoring data showed that the water quality of streams flowing into Lake Paldang has been improved by various strategy for water. However, the effect of quality on Lake Paldang is still insufficient because of nonpoint source from watershed. In order to evaluate quantifying methods for pollution source and make a suggestion on improvements, Storm Water Management Model (SWMM) was constructed by using data set from the water quality and streamflow monitoring network in the Kyoungan watershed for Total Maximum Daily Loads (TMDLs). Load duration curve (LDC) based on the result of the Kyoungan watershed SWMM indicated that the water quality criterion on $BOD_5$ was often exceeded in up-stream than down-stream. From flowrate-load correlation curve, SS load significantly increased as streamflow increases. 75.3% of streamflow and 62.1% of $BOD_5$ loads is discharged especially in the zone of high flows, but monitoring data set didn't provide proper information about the conditions and the patterns associated with storm events. Therefore, it is necessary to acquire representative data set for comparing hydrograph and pollutograph through monitoring experimental watershed and to establish methods for quantifying point and nonpoint source pollutant loads.

• 한국환경과학회지
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• 제13권3호
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• pp.251-262
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• 2004

To identify the characteristics of wastewater flow generated in treatment basins of Seogwipo-city, we selected 3 stations representing the basin and performed 7 times of field survey including 5 times in dry periods and 2 times in wet periods from Feb. 25 to May 27, 2002 for the selected stations. From the analysis of flow data measured for more than 60 days in the interval of 5 minutes and concentration data obtained from laboratory analysis, we can draw several conclusions. First, in the analysis of diurnal variation of wastewater flow for land-use types, we could find the following results: in the residential area, it is observed that wastewater flow rates rise early in the morning for the office-going hour and fall gradually and rise again after the office-leaving hour, showing typical residential wastewater flow pattern, while for the residential and commercial area flow rates rise early in the morning at the office-going hour and move up and down repeatedly within wide range and last till the office-leaving hour, which can be resulted from wastewater that is generated by tourists activated after early in the afternoon, while for the touristy area flow rates rise early in the morning and fall gradually and rise again within wide range. Second, in the analysis of temporal variation of wastewater flow for monthly, it can be observed that in the residential area, in the residential and commercial areas the flow rate of May is higher than that of Feb., March, while for the touristy area flow rate is without monthly because it reflects the movement of population, Third, in wet periods concentration of water-quality item such as SS, BOD, and COD_{cr}$ is high in the beginning of rainfall by first flush, and falls down gradually to reach the steady state, which is the level of wastewater in dry periods after the cease of storm water due to diluting effect resulting from additional runoff water through storm sewers.

• 상하수도학회지
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• 제24권4호
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• pp.443-451
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• 2010

This study was conducted to confirm the CSOs characteristics, and to estimate treatment efficiency of CSO treatment process. Flowrate was average $53,500m^3$/d, maximum $58,100m^3$/d during dry season, but after rain-fall, the flowrate was increased more than twice that of the dry season. And, water pollution concentrations, such as $COD_{Cr}$, SS, $BOD_5$, TN and TP of after rain-fall, were also increased. Thus, for more efficient treatment of pollutants during rainy season, The vortex separator and continuous fiber filter devices were used. From the results on particle range, removal efficiency of particle was 99.7% at the particle size range of $40{\sim}100{\mu}m$ but decreased as 55-80% at the below $40{\mu}m$. The removal efficiencies of $COD_{Cr}$, SS, TN and TP were approx. 70, 60, 70 and 50, respectively during the dry season and approx. 50, 50, 8 and 18% during the rainy season. Also, when compared with the primary sediment basin, $COD_{Cr}$, SS, TN and TP removal efficiencies were high. especially, at the case of TN and TP, TN was more removed than TP because of higher conversion factor value. But we needed more study for the injection of a coagulants to get more stable treatment efficiency for soluble pollutants. Consequently, This process can be used for CSOs treatment as well as replace the primary sedimentation basin during the dry season.

• Environmental Engineering Research
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• 제25권4호
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• pp.498-505
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• 2020

This study analyzes the velocity and pressure incurred by protruding shapes installed within the inlet part of a pressurized membrane module during operation to determine the fluid flow distribution. In this paper, to find the flow distribution within a module, it investigates the velocity and pressure values at cross-sectional and outlet planes, and 9 sections classified on outlet plane using computational fluid dynamics. From the Reynolds number (Re), the fluid flow was estimated to be turbulent when the Re exceeded 4,000. In the vertical cross-sectional plane, shape 4 and 6 (round-type protrusion) showed the relatively high velocity of 0.535 m/s and 0.558 m/s, respectively, indicating a uniform flow distribution. From the velocity and pressure at the outlet, shape 4 also displayed a relatively uniform fluid velocity and pressure, indicating that fluid from the inlet rapidly and uniformly reached the outlet, however, from detailed data of velocity, pressure and flowrate obtained from 9 sections at the outlet, shape 6 revealed the low standard deviations for each section. Therefore, shape 6 was deemed to induce the ideal flow, since it maintained a uniform pressure, velocity and flowrate distribution.

• 한국물환경학회지
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• 제20권6호
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• pp.563-570
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• 2004

Phased isolation intrachannel clarifier ditch process developed in this study is an enhanced biological nutrient removal process employing two ditches with intrachannel clarifiers. Bench-scale phased isolation ditch process was used to evaluate the system performance on municipal wastewater and detailed assessment of internal behavior in a ditch and each reactions. When the system was operated at the HRTs of 6~12hours, SRTs of 9~31 days, and cycle times of 4hours, the system showed removals of BOD, TN, and TP as high as 88~97%, 73~78%, and 65~90%, respectively. The internal behavior were well matched on each reactions such as nitrification, denitrification, and phosphorus release and uptake. As the SRT became longer, TN removal increased gradually, whereas TP removal decreased contrarily. However, the system was capable of producing an effluent TP concentration 1mg/L or less even at longer SRTs except the case of solids discharge by malfunction of intra-clarifier occurred by its geometrical limit. The system performance slightly decreased by hydraulic shock loading(increasing of influent flowrate and decreasing of system HRT). However, the higher system performance could be achieved again after four cycles. Thus, the system reliability could be successfully achieved short-term hydraulic shock loading that occurred in medium- and small-sized wastewater treatment plants suffering fluctuation of influent quality and flowrate during wet season.