• Title, Summary, Keyword: Sedimentation basin

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Numerical analysis of flow and settling efficiency in a sedimentation basin (수치모의를 통한 침사지에서의 흐름 및 침사효율 해석)

  • Kim, Dae-Guen;Kim, Sung-Man;Park, Won-Cheol
    • Journal of Korean Society of Water and Wastewater
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    • v.24 no.6
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    • pp.713-722
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    • 2010
  • 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.

Three-dimensional numerical modeling of sediment-induced density currents in a sedimentation basin (3차원 수치모의를 통한 침사지에서의 부유사 밀도류 해석)

  • An, Sang Do;Kim, Gi-Ho;Park, Won Cheol
    • Journal of Korean Society of Water and Wastewater
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    • v.27 no.3
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    • pp.383-394
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    • 2013
  • 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.

Evaluation of the Effects of the Longitudinal Baffle on Settling Efficiency within Rectangular-shaped Sedimentation Basin (장방형 침전지내 도류벽의 침전효율에 대한 영향 평가)

  • Park, No-Suk;Kim, Seong-Su;Seo, In-Seok;Min, Kyong-En
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.5
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    • pp.573-581
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    • 2009
  • In the case that the average velocity within rectangular-shaped sedimentation basin is less than 1.5cm/sec, and Froude number less than $10^{-6}$, it can not be expected that the longitudinal baffle improves the sedimentation efficiency. Also, since relatively lower velocity increases the effect of geostrophic body force, asymmetric flow pattern on a plane occurs within the basin. From the results of CFD (Computational Fluid Dynamics) simulation, in the case that the highest velocity within rectangular-shaped sedimentation basin is over 1.5cm/sec, and Froude number over $10^{-6}$, it can be expected that the longitudinal baffle installed within rectangular-shaped sedimentation basin improves the sedimentation efficiency.

Evaluation of the Effect of Sedimentation Basin Structure on Hydrodynamic Behavior using CFD(I): The Effect of Longitudinal Baffle (CFD를 이용한 침전지 구조가 수리거동에 미치는 영향 평가(I): 도류벽의 영향)

  • Park, Se-Jin;Park, No-Suk;Lim, Jae-Lim;Kim, Sun-Kyu;Kim, Sug-Goo;Mun, Yong-Taek;Bang, Ki-Woong
    • Journal of Korean Society of Water and Wastewater
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    • v.20 no.5
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    • pp.667-676
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    • 2006
  • This study was conducted to evaluate the effect of longitudinal baffle on hydrodynamic behavior within a certain full-scale sedimentation basin (flow rate per basin; $1,000m^3/d$). Comparative experimental investigations have been carried out on the sediment removal efficiencies and the sludge deposit distribution in the baffled and un-baffled sedimentation basin, respectively. From the results derived in the baffled and un-baffled sedimentation, the turbidity removal rate in the baffled sedimentation basin is about 38% higher than that in un-baffled. Also, the height of sludge deposit in the baffled sedimentation basin is approximately 20% lower, and the sludge concentration is 10% higher than those in un-baffled sedimentation basin. In order to explain the experimental results and investigate the effect of longitudinal baffle in more detail, we conducted Computational Fluid Dynamics (CFD) simulation. From the results of CFD simulation, the flow, especially in the near of outlet orifice, was more stable in the case of longitudinal baffled sedimentation basin than that in un-baffled basin. Also, it could be concluded that the longitudinal baffle made a fully developed flow more effective for sedimentation.

Water Purification Characteristics of Sedimentation Basin for Agricultural Water Quality Improvement (농업용수 수질개선을 위한 침강지의 수질정화 특성)

  • Kim, Hyungjoong;Kim, Donghwan
    • KCID journal
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    • v.21 no.1
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    • pp.55-63
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    • 2014
  • A sedimentation basin for agricultural water quality improvement was researched to analyze the water quality purification characteristics. The sedimentation basin constructed at the inlet of Gamdon reservoir in Muan-gun, Jeollanam-do was selected as the research field of this study. The surface area of the sedimentation basin is $34,000m^2$, volume is $122,000m^3$, and hydraulic retention time is 0.3hr~7.3day. The average influent loading of SS was 156.6kg-SS/d, and the effluent loading was 67.5kg-SS/d with the average removal rate of 56.9%. The average influent loadings of BOD and COD were 33.0kg-BOD/d and 60.3kg-COD/d respectively, and the effluent loadings were 26.4kg-BOD/d and 48.6kg-COD/d with the average removal rate of 20.1% and 19.3% respectively. Therefore, the results of this study show that a sedimentation basin can purify SS and organic matters. The average influent loadings of T-N and T-P were 28.7kg-TN/d and 2.97kg-TP/d respectively, and the effluent loadings were 16.3kg-TN/d and 1.41kg-TP/d with the average removal rate of 43.0% and 52.6% respectively. In conclusion, the overall results of this study show that a sedimentation basin is a feasible alternative to purify organic matters and nutrients.

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A study on sedimentation characteristic according to concentration change of top soil lost by flood (유실토양의 농도변화에 따른 침강특성에 대한 연구)

  • Jeon, Young-Bong;Kang, Seon-Hong
    • Journal of Korean Society of Water and Wastewater
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    • v.28 no.5
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    • pp.581-587
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    • 2014
  • Sediment basin that is typical facility installed for development business to prevent soil erosion has low removal efficiency and therefore, it causes complaints from the residents and has a bad effect on ecosystem. Thus there is a limit to control soil erosion using the existing design methods of sediment basin, so the purposes of this study is providing suitable design factors for sediment basin with regarding soil characteristic of development areas and analysing sedimentation characteristic by inflow concentration changes. The results, for analyzing the sedimentation characteristic by soil concentrations within approximately 2,000 ~ 20,000 mg/L of initial SS concentration, indicated similar sedimentation trends for same soil in the supernatant regardless of initial concentrations. However, for different soil characteristic (percent finer), there are different results in sedimentation rate and concentrations of the supernatant. Thus it is recommended that sediment basin to prevent soil erosion during construction should be designed based on retention time derived from soil sedimentation experiments regardless of inlet concentration. In addition, installing the soil erosion prevention facility at the back to satisfy effluent water quality should be considered to minimize soil erosion effectively.

The Effect of Open Ratio of the Inlet Baffle on Hydraulic Behavior within a Rectangular Sedimentation Basin (장방형 침전지 유입 정류벽 유공비의 지내 수리거동에 미치는 영향 연구)

  • Park, No-Suk;Kim, Seong-Su;Lim, Sung-Eun;Lee, Doo-Jin;Seo, In-Seok
    • Journal of Korean Society of Water and Wastewater
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    • v.23 no.3
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    • pp.345-352
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    • 2009
  • The purpose of inlet baffle is to distribute the flow uniformly over the entire cross-sectional area of the sedimentation basin. The goal when designing this baffle is to achieve some head loss while keeping the velocity gradients through the ports equal to the velocity gradient in the end of the flocculator, so as to not break up the flocs. Sedimentation tank performance is strongly influenced by hydrodynamic and physical effects such as inlet design. This study was conducted to evaluate the effect of open ratio of the inlet baffle on hydraulic behavior within a rectangular sedimentation basin using CFD simulation and ADV technique. In order to verify the CFD simulation, we measured the factual velocity at 18 points in the full-scale sedimentation basin at Y water treatment plant. Good agreement was obtained between the CFD predictions and the experimentally measured data. From the simulation results of the existing basin with 7.4 % open ratio, it was investigated that extreme decrease in velocity occurred in the middle of basin. Since then, flow features was unstable. The region which the velocity decrease rapidly moved forward to the flow direction in proportion to the increase of inflow velocity. Also, it was investigated that the flow characteristic of 6.0 % open ratio was significantly different from 7.4 % open ratio at the same configuration condition. These results are a clear indication that inflow momentum and open ratio are the parameters affecting the characteristics of hydraulic patterns. The influence of these parameters on the sedimentation performance requires further study.

Research of Sludge Quantity and Evaluation of Sludge Handling Facilities in Water Treatment Plants (정수 슬러지 발생량 조사 및 슬러지 처리시설의 공정평가)

  • Moon, Seong-Yong;Kim, Seung-Hyun
    • Journal of Korean Society of Water and Wastewater
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    • v.18 no.3
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    • pp.279-290
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    • 2004
  • Sludge quantity has increased at "A"water treatment plant due to deterioration of raw water quality and GAC installation. Increased sludge resulted in overloading on sludge handling facilities. The object of this study is to survey sludge quantity and capacity of sludge handling facilities at "A"water treatment plant. Measured quantity of sedimentation sludge considerably exceeded the design capacity of sludge holding basin. Sludge holding basin was properly designed, but low concentration of sludge discharged from sedimentation basin caused production of large volume of the sludge. Timer operated control system for sludge withdrawal unit and leakage through a control valve were suspected to cause the low concentration. Augmentation of the control system by a turbidity meter and addition of a new control valve successfully reduced the sludge volume enough to satisfy the design capacity of sludge holding basin. Unlike sedimentation sludge, measured quantity of washwater was considerably less than the design capacity of washwater basin because it was over-designed.

A Study on effective Discharge Equipment for Sedimentation Basin (효율적인 침전슬러지 배출설비에 관한 연구)

  • Park, Jae-Kyeoung;Oh, Sueg-Young;Lee, Nam-Young;Oh, Jeong-Jin
    • 유체기계공업학회:학술대회논문집
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    • pp.259-264
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    • 2003
  • This research inspects discharge state of inside of sedimentation basin, md, through the aboard literature and data, examine sedimentation sludge about discharge plan of effective sedimentation sludge that can discharge in state of high concentration.

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Analysis of Attached Algae and Microbial Community Structure in Sedimentation Basin of Water and Wastewater Treatment Plant (정수 및 하수처리공정 중 침전지 부착조류 및 미생물 군집구조 해석)

  • Lim, Byung-Ran;Ahn, Kyu-Hong;Song, Kyung-Gun;Park, Yu-Jung;Jun, Dae-Young
    • Journal of Korean Society of Water and Wastewater
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    • v.19 no.1
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    • pp.61-67
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    • 2005
  • The objective of this study was to investigate community structure of attached algae and microbes in sedimentation basin of water and wastewater treatment plants by using respiratory quinone profile. There was an evident difference, in microbial community structure and attached algae species, between inclination plate settler and drainage canal in the sedimentation basin. The algae was composed of species in following order; Chlorophyceae>Bascillariophyceae>Cyanophyceae. The dominant quinone types of attached microorganisms in the wastewater treatment plant were plastoquinone (PQ)-9, vitamin(V)K-1 followed by UQ-8, but those for water treatment plant were VK-1, PQ-9 followed by UQ-8. These results suggests that nutrients, seasons and material of sedimentation basin have notable influence on composition of attached algae and microbial community structure in water and wastewater treatment plants.