Water Technologies > Case Studies > Degremont/Suez (CH/Fr)

Ozonated water in a baffled-contactor water purification plant



Overview: Urban wastewater market is growing rapidly, representing approx. half the world’s water treatment activities. Companies are seeking efficient solutions (e.g. Ozonation) for wastewater treatment plants that restore high-quality water, whilst respecting the environment. The process of ozonating water is known to produce pure water free of bacteria, viruses, spores, parasites, and chemicals. CFD modelling helps design such treatment plants at the operation level, e.g. fluids mixing and chemical reaction, as well as for plant interiors (baffles) and dimensions. It is important in practice to estimate the flow path and associated recirculation zones at which the mass transfer of Ozone is intensified.

The challenge: Engineers face the challenge to properly dimension the plant and its interior for the specified/operational mass-flow rates such as the fluids are well mixed right downstream the injection, ensuring a high gas surface-area, an efficient chemical reaction and a long-enough residence time of the species in play to promote inter-phase mass transfer. If indeed the ozone is bubbled through the water long enough, the ozonated water increases its purity. Simulation-based design here is also meant to optimize the type of gas injection mechanism and position in the plant.

TransAT Solution: This is a three dimensional problem for which transient RANS multiphase flow equations are solved, while switching on the chemical reaction module, accounting for mass exchanges between the fluid phases and at the wall contact surfaces. The k-? model for turbulence was used. The computational domain for the 0.27m3 laboratory scale contactor was meshed with 33.000 cells. The solution seen here does not yet assume multiphase flow, but it considers mass transfer at the internal walls.

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Dr Karol Swiderski
ASCOMP Switzerland
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