• 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.

• Environmental Engineering Research
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• v.14 no.4
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• pp.238-242
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• 2009

This study investigated the effects of organic loading rates on simultaneous carbon and nitrogen removal in an innovative fixed-film aerobic bioreactor. The fixed-film bioreactor (FFB) was composed of a two-compartment aeration tank, in which a synthetic filamentous carrier was submerged as biofilm support media, and a settling tank which polyvinylidene media (Saran) was used as settling aid for suspended solids. Three different organic loading rates, ranging from 0.92-2.02 kg chemical oxygen demand/$m^3$/day were applied by varying hydraulic retention time (HRT). The total soluble organic carbon removal efficiencies were in the range of 90-97%. The removal efficiency of ammonia was found to be in the range of 70-84%. Total nitrogen removal efficiency was found to be in the range of 40-45%, which indicates that denitrification reactions occurred simultaneously in the attached biofilm on the fibrous media in the aeration tank. The settling performance of suspended solids was significantly improved due to the presence of Saran media in the settling compartment, even for a short HRT. The fixed-film aerobic bioreactor used in this study demonstrated efficient treatment efficiency even at higher organic loading rates and at short HRTs.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.1
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• pp.103-108
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• 2010

Until now, research reports that it is difficult for brokenup floc after coagulation to reaggregate and settling efficiency of reaggregated floc is relatively low have dominated in water treatment process. In contrast, from recent study conducted by the French researcher, because the density of the reaggregated floc was higher than the previous floc, the settling efficiency of reaggregated floc increased. In this study, 15 times wet test were carried out and the removal efficiency of reagrregated floc was considerably increased. Moreover, this result was explained using the turbulent model for the flow occurred around the floc. Consequently, in the case of suitable hydrodynamic condition for the reaggregation, the characteristics of the reaggregated floc was changed into the favorable condition for improvement of settling efficiency. Also, the most important factor for reaggregation of floc was governed by hydrodynamic shear stress.

• Journal of Korea Water Resources Association
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• v.37 no.4
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• pp.293-304
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• 2004

Sedimentation basin plays an important role in urban water treatment, and there are many complicated phenomena which need to be understood for efficient design and control of it. Especially, the study on the improvement of settling efficiency is required. In this study, commercial CFD (Computational Fluid Dynamics) program, FLUENT, and particle tracking method were used to simulate the flow in sedimentation basin, and to predict the settling efficiency. Computational domain of real scale was made, and detail factors such as porous wall, and outlet trough were considered instead of being simplified. The simulation results were compared with the experimental data to calibrate the parameters of particle tracking method. Sensitivity analysis showed that the particle diameter had more significant effects on settling efficiency than the particle density. The computation results gave the best agreements with the experimental data, when the value of particle diameter was 26.5 ${\mu}{\textrm}{m}$.

• Membrane and Water Treatment
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• v.8 no.5
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• pp.423-435
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• 2017

Settling Basins are one of the most important and popular methods for removal of suspended sediments irrigation and drainage networks or power canals taking off from an alluvial river and wastewater treatment plant. Improving the performance and so increasing sediment removal efficiency of settling basins by an alternative method is necessary. In the present work, the effect of baffle and its angle of attack with the flow (${\theta}$) on the sediment removal efficiency is investigated by conducting a series of experiments on a straight canal with 8 m length, 0.3 m width and 0.5 m height and 3 m length of basin equipped with an adjustable glass baffle. A numerical analysis has been carried out using ANSYS Fluent 3D software (a general purpose computational fluid dynamics simulation tool) for three Froude numbers from the experiments. The numerical and experimental results were found to match reasonably well.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.4 s.107
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• pp.67-76
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• 2004

Because paper industry spends lots amount of water, the recycling of water is very important in economical as well as environmental aspects. In order to optimize the process water recycling system, the efficiency of unit operation for water circulation, such as save-all system, CDS and settling tank, plays an important role in. In this study, the sedimentation efficiency of process water was evaluated by SS measurement with the different amounts of flocculent addition. 3 different kinds of process water were collected from fine paper mill, and applied in laboratory sedimentation equipment for the measurement of settling efficiency of SS materials. The addition amounts of alum and PAC were resulted in optimum efficiency of sediments in the condition of 100 ppm of alum and 500 ppm of PAC respectively. In the comparison of sedimentation efficiency between alum and PAC, alum showed more economical and efficient results. The SS of spill water and the particle size of suspended materials treated by alum flocculents were below 50 ppm and about 1 $\mu$m. It would be considered that the spill water can be substituted to superclear water grade.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3B
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• pp.153-159
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• 2012

In this study, we proposed modified settling basins transformed by substituting the downstream sill for low head weirs such as generic labyrinth weir and inclined crest labyrinth weir worked as internal baffles. Laboratory experiments were carried out to understand hydraulic characteristics inside of the settling basin to improve the efficiency of sedimentation rate. For a quantitative analysis, we suggested the headwater ratio($H_t/P$), the magnification ratio(L/W) and the inflow rate per total crest length($q_L$) as primary analysis indexes for sedimentation efficiency. Six different types of settling basin were used for labscaled pilot tests by distinguishing with internal structures. Based on results, the variation of headwater ratio with the change of magnification ratio would highly affect the deposition efficiency(%) and it was improved under specific condition that repeating arrange number(N) of labyrinth weir was between 2 and 4. Also, the regression analysis showed that initial condition and shape for improving sedimentation efficiency were plotted on the graph for both $q_L{\geq}3.5cm^2/s$ and $L/W{\leq}3.5$. It would be expected that the geometrically optimized labyrinth settling basin could be designed with proper deposition efficiency for inflow rates of influent and required area of settling basin utilizing the proposed analysis index in this study.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.5
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• pp.609-614
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• 2014

Researcher of this study improved conventional circle secondary settling basin, through the way such as extend of inlet pipe length, introduction of device for inducting uniforming of flow, keeping of height of sludge interface. Also, we compared conventional circle settling basin to improved circle settling basin the water treatment efficiency. Result of research, when SVI is average 117, improvement rate of SS and BOD were 51.0%, 37.0% approximately compared to conventional settling basin. And when SVI is average 178, improvement rate of SS and BOD were 22.7%, 36.0% approximately. Also when SVI is average 196, improvement rate of SS and BOD were 24.7%, 30.3% approximately. When it's winter, improvement rate of SS, BOD, COD, TN and TP were 20.6%, 17.9%, 13.9%, 13.5%, 12.4% approximately. Therefore, we can be the judge, this improved settling basin can be used as the final settling basin in the waste water treatment plant.

• Journal of Environmental Science International
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• v.25 no.9
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• pp.1233-1239
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• 2016

This study aimed to evaluate changes in the TN and TP removal efficiencies, depending on whether or not a settling process is applied, in a sequencing batch reactor (SBR) process with a membrane bioreactor (MBR). Nutrient removal was considered in terms of developing an advanced water treatment system for ships in accordance with water quality standards set forth by 227(64). For these purposes, the TN and TP concentrations in the inflow and outflow water were measured to calculate the TN and TP removal efficiencies, depending on whether or not a settling process was used. Water discharged from a bathroom, which was constructed for the experiment, was used as the raw water. The experiment that included a settling process was conducted twice, and the operating conditions were: aeration for 90 min, settling for 30 min, agitation for 15 min, and settling for 15 min for one experiment; and aeration for 150 min, settling for 45 min, agitation for 15 min, and settling for 15 min in the other. Operating conditions for the experiment that did not include a settling process were: aeration for 180 min and agitation for 60 min. The concentration of the mixed liquor suspended solids (MLSS) in the reactor was 3,500 mg/L, while the aeration rate was 121 L/min and the water production rate was 1.5 L/min. For the two experiments where a settling process was applied, the average TN removal efficiencies were 44.39% and 41.05%, and the average TP removal efficiencies were 47.85% and 46.04%. For the experiment in which a settling process was not applied, the average TN removal efficiency was 65.51%, and the average TP removal efficiency was 52.51%. Although the final nutrient levels did not satisfy the water quality standards of MEPC 227(64), the TN and TP removal efficiencies were higher when a settling process was not applied.