Abstract
Hydrogen sulphide (H2S) is a toxic malodorous gas emitted by wastewater treatment plants (WWTP). In this study, two approaches to estimate H2S emissions from an anaerobic WWTP lagoon were employed: a mathematical model based on the WATER9 equations and a direct measurement by dynamic flux chamber. H2S emissions measured with the flux chamber presented correlation with some lagoon parameters depending on where the flux chamber was placed. At the lagoon inlet, only the dissolved H2S concentration influences the H2S emissions, in the middle and at the outlet of the lagoon, biogas bubbles presence prevent from finding such correlation. However, at the lagoon outlet, the liquid temperature had more influence on H2S emissions. Emission fluxes obtained by the mathematical model are overestimated by a factor of seven in relation to the flux chamber measurements. Both methods have limitations regarding the wind speed. It was found that the mathematical model overestimated the gas-liquid interface frictions, leading to the overestimation of the calculated H2S emissions and the dynamic flux chamber underestimates the same frictions, leading to the underestimation of the measured H2S emissions. Moreover, even when the wind speed was set equal to 1m s-1 for the mathematical model, obtained emissions are overestimated in relation to the dynamic flux chamber emissions measurements by a factor of three. This means that the dynamic flux chamber reduces H2S molecular diffusion of the volatilization process.
