수치모의를 통한 침사지에서의 흐름 및 침사효율 해석

김대근,김성만,박원철 대한상하수도학회 2010 상하수도학회지 Vol.24 No.6

This paper has assessed the flow patterns and settling efficiency in the sedimentation basin using the particle tracking method of the CFD code and has reached the following conclusions: In the original design where no baffle is installed in the sedimentation basin, a large recirculating area where the flow stagnates is created in the right side of the sedimentation basin, with most of the particles moving to the left side of the sedimentation basin following the flow. This biased flow structure in the sedimentation basin reduces the residence time of particles and thereby undermines settling efficiency. The biased flow toward the left side of the sedimentation basin is alleviated by installing a baffle in the sedimentation basin, promptly reducing the fast flow of over 0.7 m/s in the inlet of the sedimentation basin to the rate below 0.2 m/s. In this paper’s simulation conditions, if a one-sided baffle is to be installed in the sedimentation basin, placing it 15 meters away from the basin’s inlet leads to the best settling efficiency; it has also been analyzed that installing a two-sided baffle—rather than a one-sided one—is a better option in terms of settling efficiency. The highest settling efficiency of 96.2% is achieved when the underwater length of the two-sided baffle is set at 8 meters.

3차원 수치모의를 통한 침사지에서의 부유사 밀도류 해석

안상도,김기호,박원철,Van Thinh Nguyen 대한상하수도학회 2013 상하수도학회지 Vol.27 No.3

A sedimentation basin is used to remove suspended sediments which can cause abrasive and erosive wear on hydraulic turbines of hydropower plants. This sediment erosion not only decreases efficiency of the turbine but also increases maintenance costs. In this study, the three-dimensional numerical simulations were carried out on the overseas hydropower project. The simulations of flow and suspended sediment concentration were obtained using FLOW-3D computational fluid dynamics code. The simulations provide removal efficiency of a sedimentation basin based on particle sizes. The influence of baffles on the flow field and the removal efficiency of suspended sediments in the sedimentation basin has been investigated. This paper also provides the numerical simulations for sediment-induced density currents that may occur in the sedimentation basin. The simulation results indicate that the formation of density currents decreases the removal efficiency. When a baffle is installed in the sedimentation basin, the baffle provides intensive settling zones resulting in increasing the sediments settling. Thus the enhanced removal efficiency can be achieved by installing the baffle inside the sedimentation basin.

유사배제를 위한 역쐐기 천공형 래버린스 보의 최적 설계인자 도출

김수영,임장혁,이승오 한국방재학회 2014 한국방재학회논문집 Vol.14 No.3

Various transverse artificial structures have been constructed in rivers and streams. A weir, one of representative transverse structures,plays a significant role in maintaining the upstream depth of water and securing water resources. However, it has generic disadvantageof undermining sediment continuity due to sediment deposition at direct upstream of weir. Because of these things, ecosystemsof the weir downstream could be effected or disturbed. In this study a trapezoidal Labyrinth weir was modified to increasesediment exclusion efficiency upstream, called as the Sediment Exclusion Labyrinth weir (SEL weir). Various effective factors, theratio of hole area (a/A), the hole number (n) and the ratio of height of holes and weir (hhole/hw), were examined in order to find optimaldesign factor with numerical simulation. As numerical results, when the ratio of hole area was less than 0.069, the reduction rateof upstream height was less than 3.0%, where the upstream water depth was approximately was maintained. When the hole numbersbecame 4, the maximum accumulated sediment exclusion efficiency was occurred. However, the role of hole number was not playedimportant to accumulated sediment exclusion efficiency. And the maximum accumulated sediment exclusion efficiency was occurredat hhole/hw=0.1. In this study, it is expected to increase sediment exclusion efficiency and availability with relatively simple and easymodification in terms of construction and management. In the future, the validation of design adequacy and sediment exclusive efficiencywill be asked through construction of model and prototype using design factors presented in this study. 하천에 설치된 대표적인 횡단구조물인 보(Weir)는 수심을 유지시켜주고 수자원(Water resource)확보에 많은 역할을 하는 구조물이다. 그러나 보는 보의 직상류에 유사(sediment)를 퇴적시키는 단점을 가지고 있다. 이는 보의 하류로는 유사가 전달되지 않아 유사연속성(sediment continuity)을 저해하며 이로 인해 보 하류부 생태계에 영향을 미치게 되며 자칫 생태계의 교란을 야기할 수도 있다. 본 연구에서는 일반형 사다리꼴 래버린스 보를 개선하여 유사배제효율(Sediment exclusion efficiency)을 증가시킨 유사배제형 래버린스 보를제안하였다. 천공의 면적비, 개수, 높이비를 주요변수로 설정하여 변화시켜가면서 수치모의하여 수심유지효과와 유사배제효율에 대한최적 설계인자를 도출하였다. 그 결과 역쐐기 천공형에 대한 설계인자인 천공면적비는 0.069 이하 일 때, 상류수심의 감소율이 3.0%이하로 수심유지효과가 보존되는 것으로 나타났으며, 천공개수는 월류벽면 당 4개 일때 최대누적유사배제효율을 나타냈으나 큰 영향을 미치지는 못했다. 천공의 높이비(hhole/hw)는 0.1일 때 최적인 것으로 나타났다. 본 연구에서는 제안된 역쐐기 천공형 유사배제형 래버린스 보는 상대적으로 간단한 시공만으로 유사배제효과를 기대할 수 있으므로 활용성이 높을 것으로 판단되며 추후 설계인자를 이용한 시공을 통해 설계인자 설정의 적절성과 유사배제효율 등의 검증이 가능할 것이다. 또한 생태적인 효과에 대한 검증도 함께 이뤄진다면 그 활용성은 더 증가될 것으로 판단된다.

경사판 칩전지의 효율 특성에 관한 연구

양원영(Yang Won-Young) 한국지적정보학회 2002 한국지적정보학회지 Vol.4 No.-

본 연구에서는 경사판침전지의 효율특성을 파악하고자 일반침전지와의 비교실험을 하였다. 경사판침전지의 실험조건이 각각의 경사판 각도 60˚, 70˚, 80˚, 90˚로 변화를 주었고, 경사판과 경사판 간격은 100㎜로 선정하여 실험을 하였다. 그리고, 일반침전지를 경사판침전지의 동일 조건에서 실험을 실시하였다. 실험결과는 경사판침전지가 경사판 각도 60˚ 이고 경사판간격 100㎜일 때, 일반침전지의 침전효율은 62%이고 경사판침전지의 71%로 경사판침전지가 일반침전지보다 효율면에서 9% 침전효율이 높은 것으로 나타났다. 따라서, 현재 대부분의 정수장에서 일반침전지를 적용하고 있는데, 앞으로 경사판침전지에 대해 많은 연구가 이루어진다면, 보다 침전효율이 높은 침전지를 정수장을 기획, 설계하는데 도움이 될 것으로 판단된다. In this paper, in order to know sedimentation efficiency of normal sedimentationㆍinclination plate sedimentation compared with laboratory test. According to inclination plate's angle of inclination plate sedimentation, as a result of laboratory get most optimized inclination plate in laboratory is inclination plate with 60° angle, and 100㎜ interval of inclination plate. Sedimentation efficiency of normal sedimentationㆍinclination plate sedimentation is 62% and 71%. Also. the rate of sedimentation was increased 9%. As a conclude, From now on, Inclination plate sedimentation requirement in study.

저수지 내 침강지의 유형별 수질정화 효율과 퇴적물 특성 변화

장정렬 ( Jang Jeong-ryeol ),최선화 ( Choi Sun-hwa ),남귀숙 ( Nam Gui-sook ),권순국 ( Kwun Soon-kuk ) 한국농공학회 2004 한국농공학회 학술대회초록집 Vol.2004 No.-

본 연구에서는 농업용 저수지 내에 체류지와 유사한 기능을 하는 침강지를 준설형, 차수막형, 보조댐형의 3가지 유형으로 조성하여 COD, T-N, T-P, SS에 대한 수질정화효율과 침강지 조성 전후의 퇴적물의 특성변화를 살펴보았다. 침강지의 정화효율은 수질항목 및 조사시기에 따라 다양한 변화를 나타내었으며 조사항목 평균으로 각각 준설형 18%, 차수막형 11%, 보조댐형 42%순으로 보조댐형이 높게 나타났고 이러한 경향은 우기에는 더욱 높았다. 보조댐형 침강지는 조성 후 퇴적물의 토성변화가 있었고 특히, Silt 성분의 침강효과가 높은 것으로 추정되었다. 현재 1,221개소의 농업용 저수지에 대한 중장기 준설계획이 수립된 바, 준설 시에 유입부를 깊게 준설하고 보조댐을 쌓는 방안을 검토하여 당초 목적한 수자원확보 뿐 만 아니라 저수지 수질관리와 사후 준설작업의 효율성을 증대시킬 수 있는 방안의 검토가 필요하다. 앞으로 침강지 내 퇴적물이 침강지 수질과 정화효율에 미치는 영향을 고려한 합리적인 준설구기에 대한 지속적인 연구가 필요하다. Three types of sedimentation basin(SB), ie., dredging, shield skirt and auxiliary dam, were constructed at the inlets of two irrigation reservoirs and were monitored to evaluate their pollutant removal efficiencies for COD, T-N, T-P, and SS. Removal efficiencies were varied wide ranges from -87.3 to 92.2 % with times and the kind of pollutants. Regression of Concentration(ROC) method was introduced to evaluate the long-term average removal efficiencies. The overall ROC efficiencies of dredging, shield skirt and auxiliary dam were 18%, 11% and 42%, respectively, and those removal efficiencies significantly increased during the rainy season. The auxiliary dam type was more effective than others to trap efficiency. It is recommended that SB, at the inlet of an reservoir, would be constructed as completely separated structure from the water body of reservoir.

저수지 내 유입부 침강지의 수질정화 효율

장정렬 ( Jeong Ryeol Jang ),최선화 ( Sun Hwa Choi ),권순국 ( Soon Kuk Kwun ) 한국물환경학회 2004 한국물환경학회지 Vol.20 No.5

A sedimentation basin (SB) at the inlet of an irrigation reservoir which was constructed using an auxiliary dam was monitored to evaluate its pollutant removal efficiency. Water sampling at three points, i.e., inflow stream, upstream and downstream of the reservoir, were taken 5 times before and after the construction of the SB in 1999 and 2003, respectively. No significant water quality variations in inflow stream were observed during these periods. The COD, T-N, T-P and SS removal efficiencies were 38, 24, 35 and 49%, respectively. The results indicated that those removal efficiencies significantly increased during the rainy season and COD removal efficiency, especially, was higher than others studies. The scale of SB in this study was rational as aspects of pollutant removal efficiency and hydraulic detention time. And it is recommended that SB, at inlet of an reservoir, should be constructed as completely separated structure from reservoir water body and having SAR Index from 0.7% to 1.0%.

시화호 인공습지에서 표층퇴적토의 오염물질 함량 분포와 제거효율 평가

최돈혁(Don Hyeok Choi),최광순(Kwang Soon Choi),김동섭(Dong Sup Kim),김세원(Sea Won Kim),황인서(In Seo Hwang),이미경(Mi Kyung Lee),강호(Ho Kang),김은수(Eun Soo Kim) 大韓環境工學會 2009 대한환경공학회지 Vol.31 No.9

시화호 인공습지내 표층퇴적토에 의한 오염물질 제거효율을 평가하기 위하여 표층퇴적물내 물질함량과 퇴적토에 의한 오염물질의 용출여부를 조사하였다. 조사기간 동안 표층퇴적물의 COD, TOC, IL, TN, TP 함량은 각각 4.1~47.7 mg/g, 0.29~2.81%, 1.88~8.15%, 0.03~0.35%, 362~1,150 μg/g의 범위로 조사지점과 시기에 따라 차이를 보였다. 유기물과 TN 함량은 봄에 높고 시간이 지날수록 감소하는 경향을 보인 반면 TP 함량은 유의적인 차이를 보이지 않았다(3월≥5월≥7월≥9월, p=0.003 for COD, p=0.001 for TOC, p=0.017 for IL, p=0.015 for TN). 표층퇴적토의 중금속 함량은 As 3.5~13.9 μg/g, Cd 0.08~0.38 μg/g, Cr 51.8~107.0 μg/g, Cu 16.4~81.8 μg/g, Pb 26.8~81.8 μg/g, Zn 85~559 μg/g의 범위로 항목에 따라 상이한 시공간적인 분포를 보였다. 퇴적물환경기준으로 볼 때 유기물 함량은 대부분 기준 이하의 수준을 보인 반면 TN과 TP는 "중간오염" 또는 "심한 오염" 수준을 보였다. 그리고 중금속 함량은 Cd과 Pb을 제외한 모든 항목에서 퇴적물 환경기준으로 초과하는 것으로 나타났다. 퇴적토의 용출실험 결과로부터 TN, Pb, Zn은 퇴적토에 의해 제거되는 반면 TP, Cd, Cu는 퇴적토로부터 용출되는 경향을 보였다. 그러므로 시화호 인공습지에서 표층퇴적토의 수질정화기능을 향상시킬 수 있는 방안수립이 필요하다. To estimate the pollutant removal efficiency by surface sediment, matter content within surface sediment and its release from the sediment were investigated at 12 sites in the Sihwa constructed wetland. The content of COD, TOC, IL, TN, and TP within sediment varied temporally and spacially, showing ranges of 4.1~7.7 mg/g, 0.29~2.81%, 1.88~8.15%, 0.03~0.35%, 362~1,150 μg/g, respectively. The contents of organic matter and TN were significantly highest in March and decreased towards fall (March≥May≥July≥September, p=0.003 for COD, p=0.001 for TOC, p=0.017 for IL, p=0.015 for TN), whereas TP content was not significant statistically in difference between sampling times. The contents of heavy metals also varied largely with sampling sites and times (As:3.5~3.9 μg/g, Cd:0.08~0.38 μg/g, Cr:51.8~107.0 μg/g, Cu:16.4~81.8 μg/g, Pb:26.~81.8 μg/g, Zn:85~559 μg/g). As compared with sediment quality guideline, the content of organic matter within surface sediment of the Sihwa constructed wetland was classified as unpolluted level. In contrast, the contents of TN, TP and heavy metals were classified as medium or severe pollution state, except some heavy metals (Cu and Pb). From the results of release experiment, TN, Pb, and Zn tend to be removed by surface sediment, but TP, Cd, and Cu have a tendency to released from sediment. Therefore, a relevant plan to improve the removal efficiency of pollutant (especially phosphorus) by surface sediment in the Sihwa constructed wetland is needed.

Design of Coanda Intakes for Optimum Sediment Release Efficiencies

Oğuz Hazar,Sebnem Elçi 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.2

When the water has to be diverted from a turbid source having a great amount of suspended materials in it, bottom intake structures such as Coanda and Tyrolean types are preferred. To perform this task, diverted water is captured by a transversal rack, and a gallery located in the control crest is utilized. This study was motivated by a search for the best design where the quality of the diverted water can be increased by screening out most of the sediments in the flow. Current work focuses on the water capture and sediment release efficiencies of both Tyrolean and Coanda type intakes through experimental work. It complements and extends existing experimental studies by considering sediment-laden flow. We used a novel sediment feeding system designed specifically for this study in the experiments. Study results pointed out that when sediment release efficiency is considered, all types of Coanda intakes having different design parameters performed better as compared to Tyrolean intakes. Water capture and sediment release efficiencies are related to parameters used in the experiments including Coanda type, rack angle, void ratio, sediment amount, and flow rate based on the statistical analyses of these parameters. An optimum design is proposed with the maximum sediment release efficiency to prevent clogging during the operation of the intakes.

Sediment Treatment by a Centrifugal Device

Oh, Jong-Min,Lee, Yong-Sik,Jo, Young-Min 한국육수학회 2001 생태와 환경 Vol.34 No.4

본 연구는 호소내 오염된 퇴적물 처리를 위한 분리 및 농축을 위한 전처리 장치로서 hydrocyclone의 이용 가능성을 평가하는 실험이다. 외국의 선행 연구자인 Rietema의 표준 규격을 참고하여 제작된 Hydrocyclone을 이용하여 분리 및 농축 실험과 유입 및 배출 시료의 물리화학적 특성을 조사하였다. 실험결과 Hydrocyclone의 장치특성 실험에서 분리 및 농축에 가장 큰 영향요소는 몸통 직경이며, 유입속도, 유입시료의 농도에 영향을 받는 것으로 조사되었다. 분리 및 농축에 필요한 한계 유입속도는 1.5m/s로 조사되었으며, Cyclon의 몸통 직경이 작고, 유입속도가 빠르며, 유입되는 시료의 농도가 낮을수록 분리 및 농축 효율이 높은 것으로 조사되었다. 재활용 가능성 평가를 위한 오염도 평가 결과 입자의 입경이 작을수록 오염도가 높은 것으로 조사되었으며, 분리 처리 결과 현저하게 높은 유기물 제거율을 보였다. The present work is to introduce the preliminary experimental results for a primary hydrocyclones process in lake sediment thickening. A few cyclones based on the Rietema standard geometry were prepared. The test particles were sediments from a local lake and waste coal fly ash for a reference test. As a result of the chemical analysis, organic contaminants were abundantly found in smaller particles in overflow. Experimental results showed that the physical characteristics of particles, configuration of the cyclone and operating variables including feed solids concentration and volumetric flow rate could affect the separation efficiency. The limiting feeding velocity for the separation and enrichment of particles was 1.5m/s, higher separation efficiency, in general, was obtained under the high velocity with the small cyclones.

준설토 산세척 시 염산 농도가 중금속의 정화효율 및 존재형태에 미치는 영향

김기범,최용주,Kim, Kibeum,Choi, Yongju 한국지하수토양환경학회 2020 지하수토양환경 Vol.25 No.1

In this study, the effect of hydrochloric acid (HCl) concentrations on removal efficiency and chemical forms of heavy metals in dredged sediment during acid washing was investigated. The removal efficiencies of Zn, Cu, Pb, Ni and Cd by acid washing were 18.4-92.4%, 7.2-83.7%, 9.4-75%, 8.1-53.4% and 34.4-70.8%, respectively. Overall, the removal efficiencies of heavy metals were remarkably enhanced with the increase of the acid strength. However, the removal efficiencies for 0.5 and 1.0 M HCl were comparable, and both cases met the Korean soil contamination standard. Based on the sequential extraction results, concentration of the exchangeable fraction (F1), the most labile fraction, increased whereas concentrations of the other fractions decreased with increasing acid strength. Particularly, the carbonate (F2) and Fe/Mn oxides (F3) fractions drastically decreased by using 0.5 M or 1.0 M HCl. The current study results verified that acid washing could effectively reduce heavy metal concentrations and its potential mobility in dredged sediments. However, the study also found that acid washing may cause significant increase in bioavailable fraction of heavy metals, suggesting the need to evaluate the changes in chemical forms of heavy metals by acid washing when determining the acid strength to be applied.