A model to relate wind tunnel measurements to open field odorant emissions from liquid area sources

Abstract

Waste Water Treatment Plants are known to have significant emissions of several pollutants from the different treatment phases. Among such pollutants, volatile organic and inorganic compounds, often having low odour detection thresholds, cause odour nuisance to the population. One of the purposes of the present work is to determine which are the more suitable methodologies to assess the odour emissions from liquid passive area sources, by means of a thorough study of the models capable of describing the volatilization phenomena of the odoriferous compounds from such sources. Several different models were evaluated for the open field emission, selecting the most appropriate one. Moreover, the models describing volatilization under a forced convection regime inside a wind tunnel device have been investigated, in order to describe the situation inside this sampling device, typically used for sampling on liquid sources. By means of experimental tests involving pure liquid acetone and pure liquid butanone, it was verified that the model more suitable to describe precisely the volatilization inside the sampling hood is the model for the emission from a single flat plate in forced convection and laminar regime, with a fluid dynamic boundary layer fully developed and a developing mass transfer boundary layer. The proportionality coefficient for the model was re-evaluated in order to account for the specific characteristics of the adopted wind tunnel device. Due to the differences between the fluid dynamic conditions in the open field and inside the hood, it was deemed useful to devise a correlation that-according to the flush rate adopted inside the chamber-is capable of computing the wind velocity at a 10 m height that would cause the same emission flux that is estimated from the analysis of the sample collected with the wind tunnel. Finally, the field of application was clearly defined for the considered models during the project, discussing the two different kinds of compounds commonly found in emissive liquid pools or liquid spills, i.e. gas phase controlled and liquid phase controlled compounds.

Mass transfer inside a flux hood for the sampling of gaseous emissions from liquid surfaces – Experimental assessment and emission rate rescaling

“…Nonetheless, the use of water evaporative flux ratio correction factors and other aspects of this approach are subjected to some important restrictions, especially if the enclosure device presents concentration build up in the headspace (discussed further in sub-section I.3 of Supplementary Material). On the other hand, recently, Lucernoni et al (2017) presented the scaling up of the emission rate measured with a wind tunnel device for compounds with gas phase-controlled volatilisation, using a model for representative values of wind speed that match the emission rate measured by the wind tunnel and allow the recalculation for other values of wind speed. However, the resulting equations are specific for the wind tunnel and the emission model adopted by those authors, and, therefore, cannot be directly extended to the case of the flux hood.…”

Combination of field inspection and dispersion modelling to estimate odour emissions from an Italian landfill

“…In the specific case of area sources, for which sampling is typically conducted by means of fluxed hoods (Bockreis & Steinberg, 2005;Capelli et al, 2013b), with the odour concentration it is possible to evaluate the Specific Odour Emission Rate (SOER), that is the odour units emitted from the source per surface and time unit [ou/m 2 /s] referred to the specific operating conditions used during sampling (Hudson et al, 2007;Capelli et al, 2009). Specific models are then required in order to relate the SOER to real field conditions (Lucernoni et al, 2017b).…”

“…Besides, the dependence of such emissions from some crucial environmental variables has not been univocally defined yet, making the quantification of LFG emissions for implementation in a dispersion model hardly applicable. If on one hand the dependence of the OER from the wind speed for other types of area sources such as liquids has been studied and verified experimentally (Capelli et al, 2009;Lucernoni et al, 2017b), proving that the OER is proportional to the speed of the wind blowing over the surface with an exponent of 0.5 (in case of laminar flow) or 0.78 (in case of turbulent flow), recent studies seem to point out that landfill surfaces need to be treated differently (Lucernoni et al, 2016b). As a matter of fact, the mechanism that regulates emissions from landfill surfaces is not forced convection but the presence of an endogenous gas flow due to the formation of LFG inside the landfill body, which is not directly affected by the wind blowing over the surface (Lucernoni et al, 2017a).…”

Odour impact assessment of a large municipal solid waste landfill under different working phases

“…These processes result in an intensive production of methane, carbon dioxide and volatile organic compounds. The volatile compounds, both organic and inorganic, characterized by a low odour detection thresholds, are typically the main responsible of nuisance to the near-living population (Lucernoni et al, 2016(Lucernoni et al, , 2017Prata et al, 2016). Although the emission of odorous compounds are not always correlated to a health risk, it is widely reported in several studies the occurrence of symptoms as headache, nausea, stress are, (Zarra et al, 2008).…”