Modelling of flow and settling in storm water sedimentation tanks

Modelling of flow and settling in storm water sedimentation tanks

Kluck, J.

Civil Engineering and Geosciences

Water Management

1994-11-01

In the near future in the Netherlands many reservoirs will have to be built to abate the pollution of the surface water by overflowing storm water from combined sewer systems [Kluck, 1992-a]. These reservoirs, called storm water sedimentation tanks, reduce the pollution in two ways. The most important is by simply storing a part of the sewage (waste water and storm water) and thus reducing the quantity of overflowing water. The second is by providing flow conditions in which particles can settle, so that the overflowing water is less polluted. There are no satisfactory design methods - taking into account the time-varying inflow - for this kind of structures. The aim of the study is to develop design methods for these tanks such that the overall efficiency of the tanks will be optimal. A mathematical model (PHOENICS package) is used to describe the flow and settling in the reservoirs. By using the time-dependent, 2-DV or 3-D mathematical model the effect of changes in lay-out for various shapes of reservoirs can be investigated under variable flows. The course of this study has been defined as follows: First a mathematical model in which only the water flow is considered will be set up. Computational results will be compared with measurements on a scale model. The flow model will be calibrated with these measurements. Next the particle movement will be modelled. Computations will be compared with experimental data and the model will be calibrated. With the validated model different designs of tanks will be judged and optimal working tanks will be designed. The work done in the period February 1992 to July 1993 is presented in four reports [Kluck, 1992-a, 1992-b, 1993-a and 1993-b] (written in Dutch). The first report presents the objectives of the research and the present design methods for storm water sedimentation tanks. In the second report the choice for using PHOENICS to set up a mathematical model has been made. Also a start has been made with setting up a model for water movement only. The next report deals with the problems encountered in modelling a varying free-surface flow. Finally in the fourth report further progress in modelling the water flow is presented. In the future the most important parts of these reports will be translated into English. The present report describes the progress which has been made from July 1993 until July 1994. In chapter 2 a brief description of the flow model is given. Chapter 3 presents the experimental setup in which measurements were carried out. In Chapter 4 the measured data are presented, together with a comparison with computations and analysis. The work done so far to simulate the sedimentation is presented in chapter 5. Finally in chapter 6 the continuation of this research is described.

sedimentation tank
settlement tank
sewer systems

http://resolver.tudelft.nl/uuid:0a42a49b-f934-4fdb-85f4-3fd792c23387

TU Delft, Vakgroep Gezondheidstechniek

Rionedproject 92-05; Report 5 of the Rionedproject: research storm water sedimentation tanks (stora project)

Institutional Repository

report

(c) 1994 TU Delft, Department of Watermanagement