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Michael K Stenstrom - One of the best experts on this subject based on the ideXlab platform.

  • The influence of wind in secondary Settling Tanks for wastewater treatment-A computational fluid dynamics study. Part I: Circular secondary Settling Tanks.
    Water environment research : a research publication of the Water Environment Federation, 2019
    Co-Authors: Michael K Stenstrom
    Abstract:

    Computational fluid dynamics model is used to understand the impact of wind on the performance of a secondary Settling Tank (SST) in a wastewater treatment plant (WWTP). Unlike most of the previous modeling studies which evaluated the wind effect on the Settling Tank in a water treatment plant, this study evaluates a circular SST in a WWTP at different current velocities and flow conditions. Performance indicators, such as effluent suspended solids and sludge blanket height, and three-dimensional hydrodynamics profiles are compared among different windy conditions and the calm condition and under different wind directions and flow conditions. The simulation results show that the existence of wind has strong negative impacts on the overall performance of the circular SST. The prediction of ESS is doubled in the circular SST under the mild wind condition. Moreover, the circular SST is more sensitive to the wind along the inlet port direction. PRACTITIONER POINTS: This is the first comparison of wind effects on a circular secondary Settling Tank Detailed computational fluid dynamics solution procedures to simulate a secondary Settling Tank Wind effects are investigated under multiple flow conditions, current velocities, and wind directions The performance of a circular secondary Settling Tank is very sensitive to the wind Wind along the inlet port direction has stronger negative impacts than it along 45° to the inlet direction.

  • The influence of wind in secondary Settling Tanks for wastewater treatment - A computational fluid dynamics study. Part II: Rectangular secondary Settling Tanks.
    Water Environment Research, 2019
    Co-Authors: Michael K Stenstrom
    Abstract:

    : Computational fluid dynamics model is used to understand the impact of wind on the performance of a secondary Settling Tank (SST) in a wastewater treatment plant (WWTP). Unlike most of the previous modeling studies which evaluated the wind effect on the Settling Tank in a water treatment plant, this study evaluates a circular SST in a WWTP at different current velocities and flow conditions. Performance indicators, such as effluent suspended solids and sludge blanket height, and three-dimensional hydrodynamics profiles are compared among different windy conditions and the calm condition and under different wind directions and flow conditions. The simulation results show that the existence of wind has strong negative impacts on the overall performance of the circular SST. The prediction of ESS is doubled in the circular SST under the mild wind condition. Moreover, the circular SST is more sensitive to the wind along the inlet port direction. PRACTITIONER POINTS: This is the first comparison of wind effects on a circular secondary Settling Tank Detailed computational fluid dynamics solution procedures to simulate a secondary Settling Tank Wind effects are investigated under multiple flow conditions, current velocities, and wind directions The performance of a circular secondary Settling Tank is very sensitive to the wind Wind along the inlet port direction has stronger negative impacts than it along 45° to the inlet direction.

  • a sensitivity and model reduction analysis of one dimensional secondary Settling Tank models under wet weather flow and sludge bulking conditions
    Chemical Engineering Journal, 2016
    Co-Authors: Ben Li, Michael K Stenstrom
    Abstract:

    Abstract In this study, we provide the sensitivity and reduction analysis of the current, most advanced one-dimensional (1-D) secondary Settling Tank (SST) model, the Burger–Diehl model, under non-ideal flow and Settling conditions. Parameter subsets suitable for the Burger–Diehl model calibration are identified. For example, under the wet-weather condition, all model parameters, except fn and Dc,0, are influential to SST performance. When filamentous bulking occurs, the outputs of the Burger–Diehl model are most sensitive to the hindered Settling parameters, v0 and rh. In terms of parameter interactions, strong interactions are found among parameters in predicting Ce. However, for Cu, SI and Fluxop under the bulking condition, the Burger–Diehl model is almost additive with negligible parameter interactions. Moreover, the sensitivity of the Burger–Diehl model outputs to parameters is highly impacted by the imposed simulation conditions, thus resulting in different parameter subsets for model calibration. For example, under the wet-weather condition, the compression Settling parameters can be as important as the hindered Settling parameters, while bulking of the sludge greatly increases the influence of the hindered Settling parameters (v0 and rh), and decreases the influence of the compression Settling parameters. In terms of model reduction, reliable reduction of the Burger–Diehl model can be achieved based on GSA results. For example, under the bulking condition, the Burger–Diehl model can be reduced to the hindered–dispersion model regardless to model outputs. The reliability of the Burger–Diehl model reduction can be evaluated based on uncertainty, and unreliable reduction can negatively impact the decision making in SST design and control.

  • optimization of Settling Tank design to remove particles and metals
    Journal of Environmental Engineering, 2008
    Co-Authors: Yingxia Li, Joohyon Kang, Masoud Kayhanian, Michael K Stenstrom
    Abstract:

    Mass reduction rates of particles and metals were simulated for a two-compartment Settling Tank composed of a storage compartment and a continuous flow compartment. Particle-size distribution, rainfall, and flow data from 16 storm events measured at three highway sites were used. The volume ratio (i.e., ratio of surface areas for a given depth) between storage and continuous flow compartment was optimized for a given design storm size to maximize total mass reduction rates of particles and heavy metals. Measured Settling velocity profiles of runoff samples were used in the simulation. Simulation results showed that in a given total design storm, larger storage compartment fractions (>0.95) enhanced the removal of smaller particles (2–104 μm) and particulate phase metals, and even a small fraction (<0.05) of continuous flow compartment effectively removed larger particles (104–1,000 μm) . A volume fraction of 0.75 for the storage compartment is suggested to optimize annual reductions of particles and assoc...

  • dynamic characteristics of particle size distribution in highway runoff implications for Settling Tank design
    Journal of Environmental Engineering, 2006
    Co-Authors: Yingxia Li, Masoud Kayhanian, Michael K Stenstrom
    Abstract:

    To understand the characteristics of particle size distribution (PSD) in highway runoff and to facilitate designing best management practices, PSD (2–1,000 μm) was monitored in seven rainfall events in the 2002–2003 rainy season at three highway sites in west Los Angeles. Most of the particles in number were less than 30 μm in diameter and more than 90% were less than 10 μm . Particle number concentration decreased rapidly to 6 mm of accumulated rainfall and then declined more slowly throughout the storm. Particle number concentration was correlated with total suspended solids (TSS) and turbidity. Grab sample particle median diameter increased with increasing TSS. A two-compartment Settling Tank was evaluated using the measured PSD and was effective in removing both small and large particles. Capturing and retaining the first 20% of the runoff volume on seasonal average can remove 40% of the total particulate load based on calculated particle mass. Using literature data for metal concentrations sorbed to ...

K. Fujisaki - One of the best experts on this subject based on the ideXlab platform.

  • Enhancement of Settling Tank capacity using a new type of tube settler.
    Water Science and Technology, 2010
    Co-Authors: K. Fujisaki
    Abstract:

    The effectiveness of a newly developed lamellar settler was confirmed by onsite experiments. The device had inclined parallel plates arranged in a vertical direction in a Settling Tank. This vertical arrangement method enables many more plates to be set compared to the conventional horizontal arrangement. As an original and distinctive innovation, both the right and left edges of the plates were closed, for removing the clear water between the plates, The tube settler modules were installed in a final Settling Tank of a sewage treatment plant. Tests conducted over a 9 months period showed that the system operated successfully and under normal operation conditions, the new device could treat almost the same flow rate as that treated by a conventional Tank, 5,000 m3/day. For storm water, the new tube settler was demonstrated to enhance the Settling Tank capacity by up to 3 times.

  • Improvement Of Settling Tank PerformanceUsing Inclined Tube Settlers
    2005
    Co-Authors: K. Fujisaki, M. Terashi
    Abstract:

    The newly developed settler is an application of the lamella settler, which arranges inclined parallel plates in the vertical direction, contrary to the usual horizontal arrangement. In this method, the separated clear water is removed directly by suction from the top end of the parallel plates. For the removal of clear water, the right and left edges of the plates are closed, to make a tube with a rectangular cross section. These are the unique and original features of the equipment. Since each Settling tube acts as a small Settling Tank, the treatment capacity is proportional to the number of Settling tubes. Based on the results of the laboratory and on-site experiments, it is shown that the new tube settler system is very effective for the enhancement of Settling Tank performance. It is also shown from a numerical estimation that the Settling Tank installed with the new system has extremely high performance compared with the conventional Settling Tank.

  • Turbidity current in a circular Settling Tank.
    Water Science and Technology, 2004
    Co-Authors: K. Fujisaki, N. Nagata
    Abstract:

    This paper deals with turbidity currents in a circular Settling Tank. A mathematical model with a k-ɛ turbulence model has been developed. Using this mathematical model, the following unique properties of turbidity currents in a circular Settling Tank are demonstrated: turbulence induced by the turbidity currents remains after most sediment particles have settled down. This residual turbulent diffusivity has a serious effect on the Settling of finer particles. This phenomenon is a very important result in this study. Especially, in the case of a smaller densimetric Froude number, which is a stronger density effect, this residual turbulence effect increases, and also decreases the removal ratio in the downstream with low concentration. Generally, the bottom density current enhances the sediment transport near the Tank bottom, while the bottom shear gives reversal influence. When the Settling velocity is high, the Settling ends under the developing stage both of the turbidity current and of the bottom boundary layer. On the contrary, if the Settling velocity is low, the sediment travels a long distance, where the boundary layer is built up, resulting in the reduction of sediment transport near the Tank bottom. The overall properties of the density-affected Settling Tank are also investigated in terms of the removal ratio.

  • enhancement of Settling Tank capacity with inclined tube settlers
    Kagaku Kogaku Ronbunshu, 2004
    Co-Authors: K. Fujisaki
    Abstract:

    この論文は横流式沈殿池の処理効率を増大させる手法を検討したもので, 沈殿池内に設置される新しい装置を提示し, その有効性を示したものである.大都市で広く採用されている合流式下水処理方式では, 豪雨時には流入量が急増するため, 流入下水の多くが簡易処理のみで放流されていた. 最近この簡易処理のみで放流される排水による水域汚染が問題となり, 下水処理場の処理能力の増強が求められている. この研究は, この問題に対する一つの解決策として, 沈殿池の水表面積を増やすことなく, その処理能力の増強をはかる手法を開発することを目的としている.まず, 横流式矩形沈殿池の挙動について, コンピュータシミュレーションを行い, 現存の沈殿池の流入負荷増に対する処理能力の限界を示した.新しく開発した手法は, 傾斜板沈殿池の考えを応用したものである. 通常の傾斜板は水平に配置されるが, 本研究ではこれを鉛直に多数並べて設置した. 傾斜板の左右両端を閉じて断面が矩形の傾斜管とし, 個々の沈降管内の上澄水を吸い上げて採取する方法について検討した. この点がこの研究の独創的な点である. 個々の沈降管はそれぞれが小さな沈殿池として機能するため, 処理能力は沈降管の数に比例する. さらにこの方式は傾斜管を鉛直に並べるため, 沈殿池の水表面積の制約を受けることが少ない.室内実験と数値解析によりこの方法の有効性を確かめた. また, この手法を実際の沈殿池に応用するための試算では, 現在の沈殿池の5倍以上の流入量の沈降濃縮処理が可能という結果が得られた.

Franci Steinman - One of the best experts on this subject based on the ideXlab platform.

  • Phenomenological Sedimentation Model for an Industrial Circular Settling Tank
    Strojniški vestnik, 2020
    Co-Authors: Leon Gosar, Brane Sirok, Franci Steinman, Tom Bajcar
    Abstract:

    The paper presents a study of the influence of integral parameters of an industrial Settling Tank on the process of sedimentation. An organic water suspension was used in the experiment where the impact of the suspension age on sedimentation was determined experimentally and by computer-aided visualization. Measurements of the inlet- and outlet suspension concentration, the difference in the level of suspension between the reservoir and Settling Tank as well as the suspension volume flow rate were carried out on a newly developed continuous sedimentation Tank. The results of the measurements served as the basis for a phenomenological multi-regression model that was developed to determine the functional dependence of the ratio between inlet- and outlet suspension concentration on the independent parameters of the process. According to the obtained results of the model, the most influential parameters of the sedimentation process are the inlet concentration and the massflow of the suspension.

  • Sedimentation efficiency of two continuously operating circular Settling Tanks with different inlet- and outlet arrangements
    Chemical Engineering Journal, 2011
    Co-Authors: Tom Bajcar, Brane Sirok, Franci Steinman, Tanja Prešeren
    Abstract:

    Abstract The paper presents an experimental study of suspension flow patterns and velocity field inside two types of circular Settling Tanks with continuous operation. The two Tanks differ in inlet- and outlet configurations. Research was focused on the influence of flow field on the sedimentation efficiency of both Settling Tanks. Experiment was carried out on a Settling Tank sections made of plexi-glass that represented radial slices of prototype circular Settling Tanks. Kinematic flow properties inside Settling Tank sections were determined by computer-aided visualization in order to analyse the whole instantaneous flow field at once. Sedimentation efficiency was assessed by measurements of inlet- and effluent suspension concentrations. Pronounced density current evolved in both Tanks, which under certain conditions enhanced sedimentation. Flow field showed qualitative changes during operation and proved to be significantly dependent on average suspension density in the inner chamber of the Settling Tank. Some important properties of the flow field could also be reconstructed from the spatial distribution of the remaining sludge. Centrally fed Settling Tank with peripheral effluent generally performed better in terms of sedimentation efficiency mainly due to insufficient height of the effluent baffle in the peripherally fed Settling Tank.

  • influence of flow field on sedimentation efficiency in a circular Settling Tank with peripheral inflow and central effluent
    Chemical Engineering and Processing, 2010
    Co-Authors: Tom Bajcar, Leon Gosar, Brane Sirok, Franci Steinman
    Abstract:

    The paper presents an experimental study of suspension flow patterns and velocity field inside a circular Settling Tank with continuous operation. Research was focused on the impact of a specific flow pattern on the sedimentation efficiency of the prototype Settling Tank. The latter differed from a common circular Settling Tank in that it was peripherally fed and had the central draw-off. Experiment was carried out on a Settling Tank section made of plexiglass and represented a radial slice of a prototype Settling Tank. The flow field and local suspension concentration was determined by computer-aided visualization. Sedimentation efficiency was assessed relatively by comparison of the amount of settled particles (sludge height measurements) between different types of flow in a certain time period of the Settling Tank operation. Results showed that there were two types of flow in the Settling Tank that were initiated by a horizontal or vertical inflow from the distribution ring. The type of inflow (horizontal or vertical) was a function of the suspension height in the Settling Tank. Significant differences in sedimentation efficiency were observed between both types of flow, particularly at lower inlet suspension concentrations. Horizontal inflow proved to be less efficient in terms of Settling.

George A. Ekama - One of the best experts on this subject based on the ideXlab platform.

  • Mass balance-based plant-wide wastewater treatment plant models - Part 4: Aerobic digestion of primary and waste activated sludges
    Water SA, 2006
    Co-Authors: S. W. Sötemann, M C Wentzel, George A. Ekama
    Abstract:

    From a theoretical investigation of the continuity of wastewater organic (COD) and N compounds along the links connecting the primary Settling Tank (PST), fully aerobic or N removal activated sludge (AS) treating raw and settled wastewater and aerobic digestion unit operations, it was found that the PS characteristics, viz. the biodegradable and unbiodegradable soluble and particulate COD and N concentrations, need to be calculated from mass balances around the PST so that the organic and N concentrations conform to continuity principles. Also, it can be accepted that the influent wastewater (fixed) inorganic sus- pended solids (ISS) concentration is conserved through the primary Settling Tank, activated sludge, aerobic digestion systems. However, the measured ISS flux at different stages through a series of wastewater treatment plant (WWTP) unit operations is not equal to the influent ISS flux because the OHO biomass contributes to the ISS flux by differing amounts depending on the active fraction of the VSS solids at that stage. The steady state activated sludge and aerobic digestion models, both modified to include the inorganic suspended solids (ISS) and the latter to include aerobic digestion of primary sludge, yielded virtu- ally identical results as Activated Sludge Model No 1 (ASM1), also modified to include the ISS. This research shows that the mass balance-based steady state activated sludge and aerobic digestion models, modified to include the ISS compound, can be coupled to produce a plant-wide WWTP model for aerobic stabilisation of sludge that can be used for design and operation and checking of simulation model results

  • Efficiency in Electricity Generation
    Water Research, 2003
    Co-Authors: George A. Ekama, S. W. Sötemann, M C Wentzel
    Abstract:

    From a theoretical investigation of the continuity of wastewater organic (COD) and N compounds along the links connecting the primary Settling Tank (PST), fully aerobic or N removal activated sludge (AS) treating raw and settled wastewater and aerobic digestion unit operations, it was found that the PS characteristics, viz. the biodegradable and unbiodegradable soluble and particulate COD and N concentrations, need to be calculated from mass balances around the PST so that the organic and N concentrations conform to continuity principles. Also, it can be accepted that the influent wastewater (fixed) inorganic sus- pended solids (ISS) concentration is conserved through the primary Settling Tank, activated sludge, aerobic digestion systems. However, the measured ISS flux at different stages through a series of wastewater treatment plant (WWTP) unit operations is not equal to the influent ISS flux because the OHO biomass contributes to the ISS flux by differing amounts depending on the active fraction of the VSS solids at that stage. The steady state activated sludge and aerobic digestion models, both modified to include the inorganic suspended solids (ISS) and the latter to include aerobic digestion of primary sludge, yielded virtu- ally identical results as Activated Sludge Model No 1 (ASM1), also modified to include the ISS. This research shows that the mass balance-based steady state activated sludge and aerobic digestion models, modified to include the ISS compound, can be coupled to produce a plant-wide WWTP model for aerobic stabilisation of sludge that can be used for design and operation and checking of simulation model results

Tom Bajcar - One of the best experts on this subject based on the ideXlab platform.

  • Phenomenological Sedimentation Model for an Industrial Circular Settling Tank
    Strojniški vestnik, 2020
    Co-Authors: Leon Gosar, Brane Sirok, Franci Steinman, Tom Bajcar
    Abstract:

    The paper presents a study of the influence of integral parameters of an industrial Settling Tank on the process of sedimentation. An organic water suspension was used in the experiment where the impact of the suspension age on sedimentation was determined experimentally and by computer-aided visualization. Measurements of the inlet- and outlet suspension concentration, the difference in the level of suspension between the reservoir and Settling Tank as well as the suspension volume flow rate were carried out on a newly developed continuous sedimentation Tank. The results of the measurements served as the basis for a phenomenological multi-regression model that was developed to determine the functional dependence of the ratio between inlet- and outlet suspension concentration on the independent parameters of the process. According to the obtained results of the model, the most influential parameters of the sedimentation process are the inlet concentration and the massflow of the suspension.

  • Sedimentation efficiency of two continuously operating circular Settling Tanks with different inlet- and outlet arrangements
    Chemical Engineering Journal, 2011
    Co-Authors: Tom Bajcar, Brane Sirok, Franci Steinman, Tanja Prešeren
    Abstract:

    Abstract The paper presents an experimental study of suspension flow patterns and velocity field inside two types of circular Settling Tanks with continuous operation. The two Tanks differ in inlet- and outlet configurations. Research was focused on the influence of flow field on the sedimentation efficiency of both Settling Tanks. Experiment was carried out on a Settling Tank sections made of plexi-glass that represented radial slices of prototype circular Settling Tanks. Kinematic flow properties inside Settling Tank sections were determined by computer-aided visualization in order to analyse the whole instantaneous flow field at once. Sedimentation efficiency was assessed by measurements of inlet- and effluent suspension concentrations. Pronounced density current evolved in both Tanks, which under certain conditions enhanced sedimentation. Flow field showed qualitative changes during operation and proved to be significantly dependent on average suspension density in the inner chamber of the Settling Tank. Some important properties of the flow field could also be reconstructed from the spatial distribution of the remaining sludge. Centrally fed Settling Tank with peripheral effluent generally performed better in terms of sedimentation efficiency mainly due to insufficient height of the effluent baffle in the peripherally fed Settling Tank.

  • influence of flow field on sedimentation efficiency in a circular Settling Tank with peripheral inflow and central effluent
    Chemical Engineering and Processing, 2010
    Co-Authors: Tom Bajcar, Leon Gosar, Brane Sirok, Franci Steinman
    Abstract:

    The paper presents an experimental study of suspension flow patterns and velocity field inside a circular Settling Tank with continuous operation. Research was focused on the impact of a specific flow pattern on the sedimentation efficiency of the prototype Settling Tank. The latter differed from a common circular Settling Tank in that it was peripherally fed and had the central draw-off. Experiment was carried out on a Settling Tank section made of plexiglass and represented a radial slice of a prototype Settling Tank. The flow field and local suspension concentration was determined by computer-aided visualization. Sedimentation efficiency was assessed relatively by comparison of the amount of settled particles (sludge height measurements) between different types of flow in a certain time period of the Settling Tank operation. Results showed that there were two types of flow in the Settling Tank that were initiated by a horizontal or vertical inflow from the distribution ring. The type of inflow (horizontal or vertical) was a function of the suspension height in the Settling Tank. Significant differences in sedimentation efficiency were observed between both types of flow, particularly at lower inlet suspension concentrations. Horizontal inflow proved to be less efficient in terms of Settling.