Dispersion Modelling of Odour Compounds Emitted by a Solid Waste Landfill in Vitória - Espirito Santo, Brazil

Abstract

Odor compounds are one of the most important pollutants related to nuisance complaints in the environmental agencies. This study presents the application of a Dispersion Modeling (AERMOD) of Odorous Gases emissions from a landfill in Vitória/Espírito Santo, Brazil, in order to evaluate the impact of its operation.Odor perception is very subjective and perceived in very low concentrations (ppb) above the perception limit (that varies between individuals – gender, age, smoker or non-smoker). Thus, is very important to work with models that solve mass transport equations in time intervals less than an hour to be possible to detect peaks concentrations.The scientific problem discussed in this abstract resides in the application of a gaussian model (such as AERMOD) to treat odor peak events in time intervals less than an hour. The potential law described by [1] was applied to obtain peak concentrations required to identify odor complaint episodes.Also, objectives of this study were: the construction of an emission inventory with the most representative sources, a better understanding of the dispersion phenomena of and create fundamentals for discussions about the impact on air quality in regions neighboring the studied plant. The computational domain was defined as a square of 400 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Meteorological data was obtained from Vitória/ES Airport Station (SBVT). The data presented was imported into the METAR code. The topographic data were extracted through the digital elevation model: SRTM3, MDE S21W041 and land use data from the region were obtained through the Environmental Agency of the State of Espírito Santo (IEMA, 2015). The emission rate for each source type were calculated by different approaches: i) The United States Environmental Protection Agency (USEPA) literature (AP-42) was consulted to obtain emission factors related to the activities that generates odorant compounds; ii) LandGEM software (Landfill Gas Emission Model) was used to obtain emission rates for landfill cells; iii) for leachate ponds the method proposed by the EPA (AP-42, Chapter 4) was also used, however, referring to the sources associated with evaporative losses in the collection, treatment and storage of wastewater; iv) the composting unit emissions were determined by emission factors proposed by Sironi et. al (2006).It was possible to establish a relation of odor concentrations between the meteorological and topographic parameters: proximity of the main sources, difference of altitude between the sources and the receptor points, predominant direction of the wind and the conditions of atmospheric stability. It is not possible to establish a predominant period of the year with the most critical results, since this analysis is related to the location of the analyzed receptor, but considering the population located at the south of the company, the period from May to August tend to present the worst results, depending on wind direction and atmospheric stability. The application of AERMOD evaluated in odor management showed identifiable concentration peaks. Significant odor emissions were from operation cells due to large areas and constant waste stream. The simulations showed that the maximum increase per hour was up to 12.20 OU/m’ converted to 2 OU/m’ in an average of 10 minutes.