Dynamic loading tests for final settling tanks

Baumer, Patrik; Volkart, Peter U.; Krebs, Peter

doi:10.2166/wst.1996.0440

Cited by 5 publications

(3 citation statements)

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“… Kim and Pipes (1996) in their assessment of the predictability of MLSS and sludge blanket depth at the Western Regional Treatment Plant in Chester, Pennsylvania during transient hydraulic conditions, noted that at peaking factors of 1.3 to 1.7 effluent suspended solid concentrations varied from 16 to 169 mg/L. Dynamic testing of final clarifiers at Zurich's Wastewater Treatment Plant revealed that doubling the overflow rate during a wet weather event can quadruple the effluent suspended solid concentration ( Baumer et al, 1996 ). While hydraulic overloading adversely affects clarifier performance by increasing overflow rate and creating turbulent nonquiescent settling, organic and suspended solid overloading increases MLSS, thus reducing the settling velocities dramatically in accordance with the Vesilind model.…”

Section: Discussionmentioning

confidence: 99%

Simultaneous Nitrification–Denitrification and Clarification in a Pseudoliquified Activated Sludge System

Nakhla

Lugowski²,

Sverdlikov³

et al. 2005

Water Environment Research

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This paper describes results from a pilot study of a novel wastewater treatment technology, which incorporates nutrient removal and solids separation to a single step. The pseudoliquified activated sludge process pilot system was tested on grit removal effluent at flowrates of 29.4 to 54.7 m 3 /d, three different solid residence times (SRT) (15, 37, and 57 days), and over a temperature range of 12 to 288C. Despite wide fluctuations in the influent characteristics, the system performed reliably and consistently with respect to organics and total suspended solids (TSS) removals, achieving biochemical oxygen demand (BOD) and TSS reductions of .96% and approximately 90%, respectively, with BOD 5 and TSS concentrations as low as 3 mg/L. Although the system achieved average effluent ammonia concentrations of 2.7 to 3.2 mg/L, nitrification efficiency appeared to be hampered at low temperatures (,158C). The system achieved tertiary effluent quality with denitrification efficiencies of 90 and 91% total nitrogen removal efficiency at a total hydraulic retention time of 4.8 hours and an SRT of 12 to 17 days. With ferric chloride addition, effluent phosphorous concentrations of 0.5 to 0.8 mg/L were achieved. Furthermore, because of operation at high biomass concentrations and relatively long biological SRTs, sludge yields were over 50% below typical values for activated sludge plants. The process was modeled using activated sludge model No. 2, as a two-stage system comprised an aerobic activated sludge system followed by an anoxic system. Model predictions for soluble BOD, ammonia, nitrates, and orthophosphates agreed well with experimental data. Water Environ. Res., 77, 98 (2005).

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Section: Discussionmentioning

confidence: 99%

Simultaneous Nitrification–Denitrification and Clarification in a Pseudoliquified Activated Sludge System

Nakhla

Lugowski²,

Sverdlikov³

et al. 2005

Water Environment Research

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“…However, the sludge was modeled by a non‐flocculent, clay suspension in their research and the effect of the porous wall on the flocculation enhancement cannot be verified. Baumer, Volkart, and Krebs () followed Krebs et al's () research and compared the effect of a solid and perforated baffle with different porosity on the performance of a pilot SST under dynamic loadings. The results showed that the perforated baffle performed better than the solid baffle under dynamic loading conditions, which can be helpful to maintain the stable performance of the SST during the wet weather.…”

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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“…Further improvements of existing secondary clarifiers can be achieved by the installation of vertical perforated walls according to Baumer et al (1996). By slowing down the bottom current, the total sludge mass stored in the final settling tank can be increased, which is especially useful in wet-weather conditions.…”

Section: Inlet Structurementioning

confidence: 99%