Flocculation modelling: a review

Thomas, David N.; Judd, Simon; Fawcett, N.

doi:10.1016/s0043-1354(98)00392-3

Cited by 395 publications

(257 citation statements)

References 48 publications

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“…On the flocculation process, one can find further information in Overbeek (1952), Dyer (1986), Winterwerp (1998), and Thomas, Judd and Fawcett (1999). About settling and deposition, one might see Kynch (1952), Richardson and Zaki (1954), Krone (1962), Mehta (1986), and Winterwerp (2002).…”

Section: On the Dynamics Of Cohesive Sediments Transportmentioning

confidence: 99%

A morphodynamic model for cohesive sediments transport

Peixoto

Rosman

Vinzón

2017

RBRH

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The dynamics of cohesive sediments in natural water bodies is of great importance for coastal engineering. Quite often, it is necessary to assess sedimentological processes in regions where cohesive sediments are prevalent, such as in many harbors. Such assessments poses challenges, especially in quantitative evaluations, as the physics involved in the transport, sedimentation and erosion of cohesive sediments is rather complex. For that, by all means, it is important to have analysis tools capable of computing cohesive sediments dynamics. This paper presents the development of a vertically averaged eulerian transport model for suspended cohesive sediments. Such model is currently available on SisBaHiA  , which is a computational modeling system developed and maintained in COPPE/UFRJ. After describing the model implementation, we present a discussion on consistency and validation tests, for each implemented mechanism within the sedimentological process, with a focus in the erosion and sedimentation fluxes. In sequence, we compare model results with the theoretical results and, for some tests, with the results of the simulations performed with the Delft3D  and Telemac  modeling systems. These models are similar to the one presented in this paper, and are well accepted and widely used on professional projects and studies. The tests showed that the developed model results were consistent for all the evaluated mechanism, and hence it's positively verified.Keywords: Erosion and sedimentation; Environmental modeling; Sediments transport; Cohesive sediments. RESUMOA dinâmica de sedimentos coesivos em corpos d'água naturais é um tema de grande importância na prática da engenharia costeira, sendo recorrente a necessidade de serem feitos prognósticos sobre esses fenômenos. Devido ao fato da física que envolve o transporte desses sedimentos ser relativamente complexa, o desenvolvimento de estudos e avaliações em projetos de engenharia se mostram um desafio. Assim, é importante que existam ferramentas de análise capazes de descrever os processos sedimentológicos para sedimentos coesivos. Nesse sentido, este artigo apresenta o desenvolvimento de um modelo euleriano 2DH de transporte advectivo-difusivo de sedimentos coesivos em suspensão. Tal modelo está disponível no SisBaHiA  , um software computacional de modelagem, desenvolvido e mantido na COPPE/UFRJ. Após a implantação, procedeu-se a etapa de verificação dos mecanismos implementados. Os resultados do modelo foram confrontados com resultados teóricos e, para alguns testes, com os resultados das mesmas simulações feitas com o Delft3D  e o Telemac  , que são modelos similares ao desenvolvido neste trabalho. Os testes confirmaram que o modelo desenvolvido apresenta resultados consistentes para todos os mecanismos avaliados, sendo assim positivamente verificado. Palavras-chave:Erosão e sedimentação; Modelagem ambiental; Transporte de sedimentos; Sedimentos coesivos.

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Section: On the Dynamics Of Cohesive Sediments Transportmentioning

confidence: 99%

A morphodynamic model for cohesive sediments transport

Peixoto

Rosman

Vinzón

2017

RBRH

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“…The G value concept, developed by Camp and Stein (1943), is widely used in designing rapid mixing and flocculation processes (Alley (2007)) and is defined by the equation (Spellman (2008) 2008)). Another parameter used in designing mixing systems is Gt, which is the dimensionless product of G and detention time t in s. Rapid mix and flocculation systems design (Thomas et al (1999)) are temperature-dependent because water viscosity varies with temperature, as shown in Table 6(a). Guidelines for adjusting detention times in both rapid mix and flocculation basins are shown in Table 6 Lu et al (1999)).…”

Section: Design Of Chemical Mixingmentioning

confidence: 99%

Review of Coagulation’s Rapid Mixing for NOM Removal

Ghernaout¹,

Boucherit²

2015

CHEM

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This review focuses on rapid mixing in the coagulation process for improved natural organic matter (NOM) removal in water treatment. Rapid mixing aims to instantly and efficiently disperse coagulant species into raw water, before flocculation, sedimentation, and filtration processes. Mechanical mixing with a longer retention time cannot guarantee an instantaneous and uniform coagulant dispersion. For this reason, the so-called pump diffusion mixer (PDM) has been proposed. Using various rapid mixing devices to test the sedimentation performance, it is showed that in-line hydraulic jet and static mixers are able to achieve performance equivalent to that of the mechanical mixing type at a lower coagulant dosage. On the other hand, the removal of NOM as disinfection by-products (DBPs) precursor by chemical coagulation (CC) has been extensively studied. It is well reported that enhanced coagulation (EC) by adjusting the pH downwards to 4-5 prior to coagulant addition will encourage the formation of soluble NOM-Al complex from low-turbidity waters. In case of most waters, therefore, acid must be added to maintain the desired coagulation pH for EC, and excess coagulant is required to improve the removal of NOM. However, CC using in-line hydraulic jet mixer such as PDM is a reasonable method for the improvement of coagulation process compared to EC, since it is possible to obtain good removals of NOM as well as turbidity using a lower dosages of coagulant without supplementary addition of chemicals for pH control and thus producing a smaller volume of waste solids.

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“…Existing basic theories, based mainly on Smoluchowski's rapid coagulation principle, allow to examine the kinetics of the coagulation process and to predict effect of aggregation expressed as the particles number reduction [3]. Further development of basic theories allow to create mathematical models of flocculation, which consider the process in greater details, namely: characterize size, strength, density of resulting flocs [4]. It is also necessary to mention that newest models take into consideration a mechanism of flocs destruction during flocculation.…”

Section: Introductionmentioning

confidence: 99%

Computer simulation of the aggregates formation during flocculation process

Rybachuk

Jodłowski

2018

E3S Web Conf.

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Abstract. The main goal of this paper is to analyse physical and chemical aspects affecting the structure and strength of flocs, which are created during coagulation and flocculation of water impurities, from the point of view of process computer simulation. Proposed mathematical dependencies were used for computer modelling of the process as well as visualisation of the obtained results. The results of algorithms operation and visualization were shown as graphical representation. Laboratory studies were carried out to check the realism of the proposed algorithm.

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Flocculation modelling: a review

Cited by 395 publications

References 48 publications

A morphodynamic model for cohesive sediments transport

A morphodynamic model for cohesive sediments transport

Review of Coagulation’s Rapid Mixing for NOM Removal

Computer simulation of the aggregates formation during flocculation process

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