The future European standard to determine odour in ambient air by using field inspection.

This paper presents the methodologies to determine odour in ambient air by field inspection that will be a new European standard. The objective is to characterise the odour in a defined area. Without making a link with potential annoyance due to the presence of odours, the described methods propose the way to characterise an exposed environment. Two approaches are defined in the new standard: the grid method and the plume method. The grid method can be used to determine the exposure to ambient odours in a defined area of study, using direct observation of recognisable odours in the field by human panel members. This method must be applied over a sufficiently long period of time (6 or 12 months) to be representative of the meteorological conditions of that location. The result is the distribution of the frequency of exposure to odours within the assessment area. The plume method can be used to determine the extent of detectable and recognisable odours from a specific source using direct observation in the field by human panel members under specific meteorological conditions.

Enhancement of ethene removal from waste gas by stimulating nitrification.

The treatment of poorly water soluble waste gas compounds, such as ethene, is associated with low substrate concentration levels in the liquid phase. This low concentration level might hamper the optimal development of a microbial population. In this respect, the possible benefit of introducing nitrifying activity in the heterotrophic removal of ethene at moderate concentrations (< 1000 ppm) from a waste gas was investigated. Nitrifying activity is known to be associated with (i) the production of soluble microbial products, which can act as (co-)substrates for heterotrophic micro-organisms and (ii) the co-oxidation of ethene. The used reactor configuration was a packed granular activated carbon biobed inoculated with the heterotrophic strain Mycobacterium E3. The nitrifying activity was introduced by regular submersion in a nitrifying medium prepared from (i) compost or (ii) activated sludge. In both cases a clear enhancement of the volumetric removal rate of ethene could be observed. When combined with a NH3 dosage on a daily basis, a gradual increase of the volumetric removal rate of ethene could be observed. For a volumetric loading rate of 3 kg ethene-COD.m-3.d-1, the volumetric removal rate could thus be increased with a factor 1.8, i.e. from 0.72 to a level of 1.26 kg ethene-COD.m-3.d-1.