Comprehensive Evaluation of Secondary Sedimentation Performance

Samstag, Randal W.; Zhou, Siping; Chan, Rick L.; Royer, Cynthia; Brown, Kevin M.

doi:10.2175/193864710798208089

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…Perforated concentric circular baffles sufficiently dissipated the inflow energy and distributed the influent flow jets along the vertical and tangential direction before entering the flocculating well. After comprehensive field‐testing and CFD modeling evaluation (Samstag, Zhou, Chan, Royer, & Brown, ), the MEDIC EDI was also recommended for North San Mateo County Sanitation District wastewater treatment plant.…”

Section: Applications Of Cfd Modeling Research and Engineering Practicementioning

confidence: 99%

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

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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

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Section: Applications Of Cfd Modeling Research and Engineering Practicementioning

confidence: 99%

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

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A Protocol for Optimization of Activated Sludge Mixing

Samstag¹,

Wicklein²

2014

proc water environ fed

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The paper outlines a protocol for comprehensive evaluation of mixing devices for activated sludge tanks using field testing for calibration of computational fluid dynamic (CFD) modeling to compare the impacts of tank and mixing device geometry on mixing and energy efficiency. The protocol includes a CFD model for activated sludge solids settling and transport which captures the influence of solids concentration gradients on fluid motion. This element of the protocol is unique in that almost all analyses completed to date for activated sludge biokinetic modeling or mixing have assumed either 1) complete mixing or 2) neutral density CFD. The protocol has been applied to date to several types of mixing devices including jet aeration and mixing, horizontal shaft propeller mixers, and diffused aeration. Field testing of several other types of mixing devices has also been accomplished. The protocol is recommended to optimize design and application of mixing devices for activated sludge service in aerated, anoxic, and anaerobic tanks as part of biological treatment processes. The approach can be extended to incorporate biokinetic models that more accurately predict the impact of tank geometry and mixer configuration on treatment efficiency than can be achieved assuming complete mixing or neutral density CFD. INTRODUCTIONWith increasing recognition of the importance of nitrogen and phosphorus removal from wastewater discharges and recognizing the proven economy of biological treatment processes for nutrient removal, the wastewater treatment industry has seen an increase in the use of unaerated tanks for anoxic uptake of nitrate and anaerobic tanks to facilitate phosphorus removal from wastewater effluents. Anaerobic tanks are also increasingly used to improve activated sludge settleability. In order to facilitate these treatment goals, biological treatment tanks with significant concentrations of suspended solids must be mechanically mixed. With this increasing importance of mixing in standard biological treatment processes, optimization of tank geometry and mixer configuration becomes more important. We want the most efficient mixing in two senses: 1) we want near uniform distribution of suspended solids across our treatment tanks and 2) we want to use tank geometries and mixer configurations that minimize consumption of energy. It is towards this optimization of mixing and energy efficiency that the proposed protocol aims. This paper is an extended version of a poster and paper prepared for the Joint WEF and IWA, WWTMod Conference (Samstag and Wicklein, 2014.)

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Comprehensive Evaluation of Secondary Sedimentation Performance

Cited by 2 publications

References 3 publications

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

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

A Protocol for Optimization of Activated Sludge Mixing

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