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T3 Three-phase simulation model for odour and corrosion in sewer systems

Doctoral student: Katharina Teuber

Supervisors: Prof. Dr. Reinhard Hinkelmann, Prof. Dr. Matthias Barjenbruch, Prof. Dr. Gunnar Nützmann

Introduction / Background

During its transportation, wastewater in sewer systems undergoes a number of physical, biological and chemical processes and transformations. Under certain conditions such as high detention times, the formation of hydrogen sulfide (H2S) in sewer systems leads to odor in the sewer atmosphere, and after a biogenic oxidation to sulfuric acid to corrosion at sewer walls. The restoration costs for corroded sewers in Germany are estimated to be in a range of billions of US $. Additionally, high concentrations of odorous substances in the sewer atmosphere can even lead to death of sewer workers.

Aims

In this project, a CFD simulation model is being developed in order to numerically describe formations across the wastewater - sewer atmosphere interface. So far, existing model approaches are one-dimensional approaches, neglecting three-dimensional flow effects in sewage and air. The three-dimensional model approach will be able to verify these assumptions and can be an extension of these models in respect to a more detailed analysis of hydraulic aspects.

The work carried out in this research divides in three different parts. The first step is a validation of the water phase described by the numerical model concerning different hydraulic conditions. Because of the fact that sewer systems are focused on in the work of this group of researchers, the consideration especially focuses on flow in closed conduits. After the first validation step is completed, the model can be used to support the experimental work of the collegiate Daneish Despot in the pilot plant of the Berliner Wasserbetriebe in hydraulic questions. The two remaining working steps are the validation of the air phase behavior in closed systems as well as the implementation of transport as well as mass transfer processes depending on factors such as Henry’s law in order to describe H2S formations. At a later stage, the model could even be extended to describe corrosion effects at the atmosphere - biofilm - sewer wall (concrete) interface and interact with project T2 (Maria Grüneberger).

Project structure
Lupe

Methods

For simulation, the open source C++ software OpenFOAM version 2.4.0, especially the multiphase-solver interFoam is being used.

Results

To validate the gas-water flow model, first the water phase behavior has been analyzed.

First test case - single phase flow
Lupe

To begin with, a single phase test case describing flow over a ground sill in a closed duct has been simulated and different turbulence models have been compared. The results have been compared to experimental results.

Second test case - two-phase flow
Lupe

In a second step, the model has been extended to two-phases and the water level drawdown has been compared to analytical results obtained by using Bernoulli and continuity equation.

Third test case - complex sewer geometry
Lupe

The model has been tested under demanding conditions by using a sewer geometry containing different geometries, flow regimes and changing flow conditions.

The results show that the simulations accurately describe the water phase behavior and the system is stable under demanding conditions.

 

Collaborations

 

Initial project plan

Zusatzinformationen / Extras

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