Olores.org Newsletter April 2022

   The legal system for the assessment of odours in ambient air is laid down in the Guideline on Odour in Ambient Air - GOAA. In several studies, the connection between the odour pollution in residential areas expressed as odour frequencies per year and the associated degree of annoyance of residents was investigated. The GOAA provides the legal framework in licensing and monitoring procedures for all types of installations.

  This legal framework is linked with the measurement methods for odour emissions at the source (olfactometry) and for odours in the ambient air (field inspection with grid measurements) as well as with a dispersion model for calculating recognisable odours in ambient air. In the GOAA, a scientifically based exposure-impact relationship is translated into limit values for odours in ambient air that also take into account differences in the annoyance potential of different odours types. In this paper, a brief overview of the results of the various investigations is given.

   The use of activated carbon has been and still is common practice in deodorization installations, as it is one of the technologies that requires the lowest initial investment, as well as little maintenance. The current situation, in which the price of this raw material is rising steadily, has led to the search for new alternatives for chemical adsorbents that allows to eliminate or minimize the use of activated carbon, while maintaining or even improving its performance.

    This study aims to present alternatives to activated carbon and compare the filtration efficiency, both in capacity and reaction rate, for hydrogen sulfide, as well as their physical characteristics. The carbon footprints of each type of adsorbent being used will also be compared. The use of nearby raw materials, together with chemical engineering for the development of these new products, makes it possible to achieve better chemical adsorbents, less pollutants, more competitive prices and what is also important, more stable prices.

    The Ondarroa WWTP receives wastewater with a very high salt load due to marine intrusion and discharges from canning industries. The high levels of SH2 in the network and in the WWTP cause serious problems of safety, odour and equipment degradation. To solve this, action has been taken in the network, reducing the contribution of sulphates at source by separating networks, reprogramming pumping and improving the management of waste from the canneries.

    At the WWTP, the water sheets have been confined, the filter presses have been replaced by centrifuges, the interior ventilation has been modelled using CFD and deodorisation has been installed consisting of two stages (biotrickling + activated carbon) for the confined atmospheres and one stage (activated carbon) for the ambient air.

    In the Flemish legislation, no odour assessment framework is implemented, despite that odour-related permit applications require the inclusion of an odour impact study. For livestock farming, odour emission factors, derived from olfactometric measurements (ou_E), are widely used. Contrastingly, the available assessment tools, based on earlier odour impact research, utilize sniffing measurements (se).

   To allow comparison between the two units of odour, it is assumed that 1 ou_E equals 1 se. For most groups of livestock animals with a rather constant growth cycle (e.g. pigs), this comparison is deemed valid and suitable for evaluating the odour impact. However, the theoretical assessment of broiler chicken emissions can be questioned, as the olfactometric emission factor of 0.33 ou_E/s.animal results in almost no odour impact.