Generalizing the effects of the baffling structures on the buoyancy-induced turbulence in secondary settling tanks with eleven different geometries using CFD models

Gao, Haiwen; Stenstrom, Michael K.

doi:10.1016/j.cherd.2019.01.015

Cited by 20 publications

(14 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Boundary conditions are shown in Table 2. Compared with our previous studies (Gao & Stenstrom, 2018a, 2018b, 2019a, 2019b, the only different boundary condition needed to simulate the windy conditions is the surface boundary condition, which is a constant horizontal velocity as the free surface along the wind direction (Gkesouli et al, 2016;Stamou & Gkesouli, 2015).…”

Section: Cfd Boundary Conditionsmentioning

confidence: 99%

The influence of wind in secondary settling tanks for wastewater treatment – A computational fluid dynamics study. Part II: Rectangular secondary settling tanks

Gao

Stenstrom

2019

Water Environment Research

Self Cite

View full text Add to dashboard Cite

Computational fluid dynamics (CFD) model is used to study the effect of wind on the performance of a rectangular secondary sedimentation tank (SST) in a wastewater treatment plant (WWTP). Unlike most of the previous CFD modeling studies which evaluated the wind effect on the sedimentation tank in only water treatment plants, this study evaluates a rectangular SST in a WWTP at different wind speeds and directions, and under different inflow loading conditions. The wind is qualitatively and quantitatively analyzed for a range of wind speeds and directions as well as loading rates. The net effect is to change the three‐dimensional hydrodynamics profiles, effluent suspended solids, and sludge blanket height. The simulation results show that the wind deteriorates overall clarification performance of the rectangular SST and has little effect on the sludge thickening under mild wind conditions until the speed increases an extreme windy condition. These CFD simulation results suggest that in strong windy climates, covering SSTs or protecting them from strong winds may be justified. Practitioner points This is the first comparison of wind effects on a rectangular secondary sedimentation tank The effects of varied flow conditions, wind directions, and velocities are compared Wind‐induced currents in the settling tank negatively affect removal efficiency Winds have strong negative impact on the performance of sedimentation tanks

show abstract

Section: Cfd Boundary Conditionsmentioning

confidence: 99%

The influence of wind in secondary settling tanks for wastewater treatment – A computational fluid dynamics study. Part II: Rectangular secondary settling tanks

Gao

Stenstrom

2019

Water Environment Research

Self Cite

View full text Add to dashboard Cite

show abstract

“…Although CFD models have been applied to study SSTs in the last three decades, there are some uncertainties of model parameters and only three recent papers (Gao & Stenstrom, , , ) studied the uncertainty of these parameters on the performance of SSTs. These model parameters are (a) generation of turbulent kinetic energy (TKE) due to buoyancy ( G b ) in the TKE equation of the k‐ε family turbulence models; (b) buoyancy coefficient ( C 3 ) in the turbulent dissipation rate (TDR) equation of the k‐ε family turbulence models; (c) turbulent Schmidt number (

σ_{c}

) in the sludge transport equation; (d) the coefficient in the second exponential term of the Takács settling equation ( r p ); and (e) dry solids density (

ρ_{p}

).…”

Section: Applications Of Cfd Modeling Research and Engineering Practicementioning

confidence: 99%

“…However, none has simulated the same cases with and without G b coupling. Therefore, Gao and Stenstrom () studied the need for coupling the G b by simulating same cases with and without coupling G b .…”

Section: Applications Of Cfd Modeling Research and Engineering Practicementioning

confidence: 99%

“…In order to generalize the effects of baffling structures on the buoyancy‐induced turbulence in SSTs, the authors used eleven SST geometries, including four circular SSTs and seven rectangular SSTs in their further study (Gao & Stenstrom, ). The results show that the G b has strong impacts on the prediction of the performance of an SST with similar poor baffling structures to the Darvill SST.…”

Section: Applications Of Cfd Modeling Research and Engineering Practicementioning

confidence: 99%

See 1 more Smart Citation

Development and applications in computational fluid dynamics modeling for secondary settling tanks over the last three decades: A review

Gao

Stenstrom

2019

Water Environment Research

Self Cite

View full text Add to dashboard Cite

Secondary settling tanks (SSTs) are a crucial process that determines the performance of the activated sludge process. However, their performance is often far from satisfactory. In the last 30 years, computational fluid dynamics (CFD) has become a robust and cost-efficient tool for designing new SSTs, modifying the geometries of existing SSTs and improved control techniques in wastewater treatment plants. The first part of this review paper discusses the different approaches to model the motion of particles in SSTs. The applications of different multiphase approaches and the widely applied single-phase approach in different SST studies are reviewed. The second part reviews current CFD research and engineering practice, focusing on the formation and the effect of density currents, effects of different design variables, parameter uncertainties in modeling structures, and atmospheric conditions. Finally, challenges and future improvements of sub-models (sludge settling, rheology, turbulence, and flocculation) in the SST model framework are identified. • Practitioner points• The first journal review for the CFD applications in SSTs over the last decade. • The controversy over the relationship between SOR and SST performance can be largely explained by the prediction of the CFD model. • Density decoupling in the turbulence model is possible for well-baffled SSTs. • The relative importance of three modeling parameters is summarized. • Recommendations for future data collection are provided. • Key wordscomputational fluid dynamics; density-driven flow; secondary settling tank; wastewater treatment

show abstract

“…The application of computational fluid dynamics (CFD) in simulating flocculation processes has been commonly found at water treatment works to increase understanding of floc formation and dissociation mechanisms [12] and optimize the flocculation tank structure [13]. In recent years, He et al [14] investigated the impeller clearance and shear rate effects on aggregation and dissociation behaviors in the whole process of flocculation growth and Gao et al [15] utilized eleven different geometry models to investigate the most effective baffling structures in secondary settling tanks by CFD.…”

Section: Introductionmentioning

confidence: 99%

Flow Field Research of the Reciprocating Baffled Flocculation Tank

Liang

et al. 2020

The 4th EWaS International Conference: Valuing the Water, Carbon, Ecological Footprints of Human Activities

View full text Add to dashboard Cite

To research the reasons for the unsatisfactory hydraulic conditions of the reciprocating baffled flocculation tank, this paper investigates its flow field through PIV (Particle Image Velocimetry) laboratory experiment tests and numerical simulation. Three numerical schemes, the standard model, RNG model and realizable model, are calibrated and validated with the experimental data gained in this study. They are adopted for comparative study of their validity and accuracy for modeling the effect of the hydraulic characteristics of the flow field on flocculation. The best validated model is then applied to explain the reasons for the low flocculation efficiency and is applied to improve the structure of the reciprocating baffled flocculation tank.

show abstract

Generalizing the effects of the baffling structures on the buoyancy-induced turbulence in secondary settling tanks with eleven different geometries using CFD models

Cited by 20 publications

References 28 publications

The influence of wind in secondary settling tanks for wastewater treatment – A computational fluid dynamics study. Part II: Rectangular secondary settling tanks

The influence of wind in secondary settling tanks for wastewater treatment – A computational fluid dynamics study. Part II: Rectangular secondary settling tanks

Development and applications in computational fluid dynamics modeling for secondary settling tanks over the last three decades: A review

Flow Field Research of the Reciprocating Baffled Flocculation Tank

Contact Info

Product

Resources

About