AIR-WATER TRANSFER OF HYDROGEN SULFIDE-An Approach for Application in Sewer Networks
Abstract:The emission process of hydrogen sulfide was studied to improve the understanding and quantification of air-water transfer of hydrogen sulfide, which are to be applied in sewer networks. Hydrogen sulfide transfer across the air-water interface was investigated at different turbulence levels (i.e., Reynolds numbers) and pH values using batch experiments. By means of the overall mass-transfer coefficient, the transfer coefficient of hydrogen sulfide was correlated to that of oxygen (i.e., the reaeration rate).
The obtained results demonstrate that both turbulence in the water phase and pH play a major role for the transfer coefficient of hydrogen sulfide. A logarithmic expression is an appropriate representation of the relationship between the transfer coefficient of hydrogen sulfide and the Reynolds number under all pH conditions studied. As expected, the transfer coefficient of hydrogen sulfide increased with decreasing pH at constant Reynolds numbers. However, the relative difference in the transfer coefficient at different pH became smaller as the Reynolds number decreased. Furthermore, the ratios between the transfer coefficient of hydrogen sulfide and the reaeration rate were, at the fixed pH conditions, observed to be constant, regardless of turbulence applied. The ratio between the transfer coefficient of hydrogen sulfide and the reaeration rate was 0.86 with a 95% confidence interval of 0.08 at pH values where only molecular hydrogen sulfide is present. This ratio was found to be equal to the ratio between the diffusion coefficient of hydrogen sulfide and that of oxygen, which was obtained from a number of empirical equations proposed in the literature. This fact was observed at all turbulence levels investigated.
Based on the findings of this study, an empirical equation that describes the dependency of the ratio between the transfer coefficient of hydrogen sulfide and the reaeration rate at a pH range of 4.5–8.0 is proposed. Theoretical and experimental aspects of hydrogen sulfide emission are discussed related to in-sewer conditions.
Document Type: Research Article
Publication date: January 1, 2002
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