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Brentwood Industries explains why the effluent quality is greatly improved out of sedimentation tanks when tube settlers are present.
6. Fong Leung & Probstein, "Lamella and Tube Settlers: Model and Operation", Ind. Eng. Chem. Process Des. Dev., 1983, 22 (1), pp 58-67.
This article explains performance in terms of a two-layer (clarified and sludge) model. Model is generalized and dimensionless and requires knowing the densities of the two layers. Recommends a spacing of 4 cm for lamella and a 2.5 cm diameter for tube settlers, but does not explain the rationale for these values.
7. Okoth, Centikaya, and Briiggemann, "On hydrodynamic optimisation of multi-channel counter-flow lamella settlers and separation efficiency of cohesive particles", Chemical Engineering and Processing, 2008, 47 (1) : 90-100.
This article claims to use a superior model that focuses on the hydraulics of the system (as opposed to describing performance in terms of mass flux); their approach may be useful for our purposes but will have to be modified to apply to cocurrent lamella. Also they apply this model to wastewater treatment, not river water treatment.
8. J. Ziolo, "Influence of the system geometry on the sedimentation effectiveness of lamella settlers", Chem. Eng. Sci. 51 (1) (1996) 149-153.
This article describes the system in terms of "sedimentation effectiveness" which mostly depends on the relative length (L/h for lamella and L/D for tube settlers). Analyzing AguaClara clarifiers in terms of this model could yield valuable spacing guidelines.
9. Chen, Y. R. (1979). Design criteria for inclined tube settlers. AIT master's thesis, Asian Institute of Technology, Bangkok.
This article is frequently referenced in literature that is of interest to us. However, since it is a Master's Thesis from an Asian university, it has been difficult to acquire. This article would be a good bet for finding spacing guidelines and possibly some analysis in terms of the velocity gradients that solid particles encounter in the clarifier (could provide comparisons for our floc rollup findings).