Using computational fluid dynamics to describe H2S mass transfer across the water-air interface in sewers.

For the past 70 years, researchers have dealt with the investigation of odour in sewer systems caused by hydrogen sulphide formations and the development of approaches to describe it. The state-of-the-art models are one-dimensional. At the same time, flow and transport phenomena in sewers can be three-dimensional, for example the air flow velocities in circular pipes or flow velocities of water and air in the reach of drop structures. Within the past years, increasing computational capabilities enabled the development of more complex models. This paper uses a three-dimensional two-phase computational fluid dynamics model to describe mass transfer phenomena between the two phases: water and air. The solver has been extended to be capable of accounting account for temperature dependency, the influence of pH value and a conversion to describe simulated air phase concentrations as partial pressure. Its capabilities are being explored in different application examples and its advantages compared to existing models are demonstrated in a highly complex three-dimensional test case. The resulting interH2SFoam solver is a significant step in the direction of describing and analysing H2S emissions in sewers.