Investigation of anaerobic zone short-circuiting using computational fluid dynamics

Sherwin, C; Ta, C. T.

doi:10.2166/wst.2002.0618

Cited by 3 publications

(3 citation statements)

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“…One of these methods is by introducing a second species which acts as the tracer and this species can be monitored at the outlet and an RTD curve plotted. Sherwin and Ta [8] used this to investigate short-circuiting in an anaerobic zone consisting of a baffle plate and two mixers. Ta and Brignal [9] used the same technique to study the residence time of a storage reservoir.…”

Section: Determination Of the Residence Time Using Computational Methodsmentioning

confidence: 99%

Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

Egarr

Faram²,

O'Doherty

et al. 2005

Proceedings of the Institution of Mechanical Engineers, Part E:

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A hydrodynamic vortex separator (HDVS) has been modelled using computational fluid dynamics (CFD) in order to accurately determine the residence time of the fluid at the two outlets of the HDVS using a technique that was developed for use in heating, ventilation, and air conditioning (HVAC). The results have been compared with experimental data [1]. It is shown that, in using CFD, it is possible to study the response to a variety of inputs, and also to determine the mean residence time of the fluid within the separator. Although the technique used for determining the residence time was developed for use in HVAC, it is shown here to be applicable for the analysis of hydraulic systems, specifically, wastewater treatment systems.

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Section: Determination Of the Residence Time Using Computational Methodsmentioning

confidence: 99%

Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

Egarr

Faram²,

O'Doherty

et al. 2005

Proceedings of the Institution of Mechanical Engineers, Part E:

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show abstract

“…no moving of the impeller is modelled. As the interactions between the mixers and the baffles or walls are weak as in oxidation ditch, this approach is powerful (Essemiani et al, 2002, Sherwin andTa, 2002). However if exact solutions are to be simulated, the sliding mesh model should be performed.…”

Section: Agitationmentioning

confidence: 99%

Trouble Shooting of Agitation in an Oxidation Ditch : Applicability of Hydraulic Modeling

Vermande¹,

Essemiani²,

Meinhold³

et al. 2003

proc water environ fed

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Hydrodynamics in an oxidation ditch is a main key of an optimal treatment. Mixing and aeration are closely linked to biological performances. One parameter considered to be essential for correct design and operation is the horizontal velocity without aeration. A value of 0.3-0.35 m.s -1 for this parameter is regarded as a prerequisite (Da Silva, 1994). Hence its correct prediction is high importance. Different CFD modelling approaches have been applied and evaluated with regard to their performance in modelling the agitation in an oxidation ditch and consequently assessing the horizontal velocity. The two approaches used differ in the way they take the agitation, i.e. the impeller, into account in the model set-up : a) the "Fixed Values" approach, imposing a local axial velocity on cylinders which represent the impellers; b) the "Multiple Reference Frame" approach (MRF), using the exact geometry of the impellers. Theses approaches are compared with experimental data, i.e. with the average horizontal velocity as well as with velocity profiles. The first CFD agitation model ("Fixed Values") is highly dependant on the quality of the information provided by the supplier of the impellers. This is due to the fact that the supplier presents the value of the imposed axial velocity for a given impeller. Hence this whole modelling approach depends on the accuracy of the value provided. However, once applying the correct axial velocity imposed, this approach can gain quite some relevance as it is less computational intensive than the MRF approach . Experimental measurements have in fact revealed a too low horizontal velocity in the oxidation ditch of concern. Thanks to the CFD simulations, presented in this study, explanations of the low horizontal velocity could be put forward. This illustrates their potential for advanced troubleshooting.

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“…The results of both numerical studies indicate that the placement and dimensions of the baffle wall are important to prevent short-circuiting and the retention of solids in suspension. Ahmed et al (1996) observed, for example, that if the opening beneath the baffle wall is small, biosolids retention in a sedimentation basin is decreased, while the numerical studies of McCorquodale et al (2007) and Sherwin and Ta (2002) suggest that there is an optimal baffle opening for solids retention. Because the geometries of the rectangular basins in these studies are substantially different than in a treatment shaft, any guidance provided by these previous studies is only qualitative.…”

Section: Introductionmentioning

confidence: 99%

Treatment Shaft for Combined Sewer Overflow Detention

Wright

Ghalib²,

Eloubaidy

2010

Water Environment Research

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A deep, large-diameter underground shaft to provide detention storage for combined sewer overflow control may be advantageous in urban environments, where space limitations require solutions with a small footprint. An underflow baffle wall is provided at the center of the treatment shaft to prevent short-circuiting of the flow. An additional objective is to maintain low headlosses through the structure. A physical model study was conducted to determine the effect of the bottom elevation of the baffle wall on the headloss and breakthrough curve for dye injected to the inflow. It was found that there is a considerable range of elevations for which the structure behaves acceptably in providing adequate contact time for disinfectant while maintaining small headlosses.

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Investigation of anaerobic zone short-circuiting using computational fluid dynamics

Cited by 3 publications

References 0 publications

Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

Computational fluid dynamic prediction of the residence time distribution of a prototype hydrodynamic vortex separator operating with a base flow component

Trouble Shooting of Agitation in an Oxidation Ditch : Applicability of Hydraulic Modeling

Treatment Shaft for Combined Sewer Overflow Detention

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