Numerical simulation of the dispersion of hydrogen sulphide emitted by a UASB reactor for domestic sewage treatment

Abstract

The anaerobic treatment of wastewaters can produce a large concentration of hydrogen sulfide (H₂S), an odorant, toxic and corrosive substance. Control methods for eliminating H₂S often require high implementation and operation costs and therefore are not used. Thus, suitable planning of wastewater treatment plant (WWTP) installation can help to prevent adverse impacts and potential problems for nearby communities. Mathematical models of atmospheric dispersion can be applied to verify the pollutant range and support the choice of the most appropriate place for installing a WWTP. Thus, the aim of this work was to analyze the dispersion of H₂S from an anaerobic unit of wastewater treatment located in a rural district of the city of Itajubá (MG), Brasil. For this, a Gaussian model AERMOD was applied using actual pollutant emission rate data in the UASB reactor, as well as meteorological and geophysical information (topography and land use). Using simulations, it was found that the odor plume was oriented by relief and concentrated near the treatment unit, limiting the impact to the rural district. The wind had also direct influence on the direction of H₂S for the first period. However, the same trend was not found in the second study period. Thus, it was found that the analysis of meteorological characteristics (especially the predominant wind direction) and geophysics in the region and the application of mathematical models can assist in choosing the most suitable location for the installation of a WWTP.