Odour Measurement

Abstract: This paper evaluates the accuracy of the newly introduced ultra-portable olfactometer,
Scentroid SM100 developed by IDES Canada Inc, with two techniques traditionally used for
assessing ambient odours: Nasal Ranger instrument and a lung technique with the dynamic
olfactometry laboratory analysis of collected samples. A similar study was presented at the recent
NOSE 2012 odour conference [1], where the results indicated good correlation between Scentroid
SM100 and other techniques used for assessing odours: a) collection of the samples at the sources
and dispersion modeling analysis to predict off site odour concentrations and b) ambient sampling
using lung technique and odour panel evaluation by dynamic olfactometry. However, the study
was based on the data when the odour was in the range 90 ou to 3000 ou. At that time the low
ranges of the Scentroid SM100 was not studied; therefore this paper is to present data based on an
extensive study of the Scentroid SM100 when the odour concentration of ambient odour is in the
range of 2 ou to 100 ou. This time the results are compared with Nasal Ranger instrument and lung
technique used for collection of ambient samples and odour panel evaluation.

Degradation is inherent part of odour sampling and olfactometery analysis. There are many techniques that can be deployed in order to minimize sample degradation, such as nitrogen-based pre-dilution and sealed transportation vessels. Despite the best efforts to keep the volatilization at bay - sample degradation has forced European and American standards to implement a thirty (30) hour expiration on all odour samples. German standard VDI3880, and possible the soon to be revised EN13725 standard, limit sample storage to 6 hours unless it can be shown that the sample degradation is within acceptable limit. Field-olfactometers such the Scentroid SM100, can be used as part of the quality assurance program by measuring samples immediately after acquisition and immediately prior to analysis by the laboratory to ensure odour degradation is within these defined limits. However, observations have shown samples can degrade by an order of ten magnitudes in a span of less than 24 hours. This study provides data on sample degradation from a variety of sources over a span of 24 hours. Samples will be stored in Nalophan, Tedlar®, and the newly introduced PTFE bags. Data has shown that the much higher density of PTFE provides slower sample degradation than Tedlar® or Nalophan. This is especially true of samples with high humidity, Ammonia, or H2S. To properly simulate shipping conditions a portion of the study focuses on samples that are subjected to lower pressure and temperature similar to those found in standard cargo planes. These samples are compared to those which have been stored at standard conditions (room temperature at 1 atmosphere).

In the modern world of wastewater treatment, control of odors has moved from an afterthought to a primary design consideration for most collection and treatment facilities. As development encroaches on our facilities and our new neighbours become less tolerant of nuisance odors, wastewater professionals have found the need to address odor as a primary concern in the design and operation of collection and treatment facilities. When facility odors affect air quality and cause citizen complaints, an investigation of those odors may require that specific odorants be measured and that odorous air be measured using standardized scientific methods. Odour intensity is one of main odour characterization parameters, and remarkably common and important sensory indicator of environmental odours. Odour intensity reflects people's perception of odours and contributes to effective odour management. The "triangle odors bag method', which has been adopted for the offensive odors control law in Japan, and the dynamic olfactometry defined by EN 13725 has been adopted in Europe. These methods are the worldwide used for as reference methods for the sensorial measurement of odours. On these methods are also based the training of electronic nose (e.Nose). In this study odour samples were collected on municipal wastewater treatment plant located in south Italy at four different treatment units to determine the relationship between odour intensity assessed by Japanese "triangle odors bag method', odour concentration measured with dynamic olfactometry according to European standard EN13725:2003 and with odour concentration measured by a novel prototype of e.Nose patented by University of Salerno. A monthly sampling and relative measurements were carried out for consecutive 12 months at Laboratory of Sanitary Environmental Engineering Division (SEED) at University of Salerno (Italy). Results show when high odours were detected by Japanese standard, the odour concentrations measured according European standard were also high (e.g. emission from sludge line). Concentrations measured by e.Nose are strongly correlated with the measurements carried out by standard methods.

Odours discharged from wastewater treatment plants generally cause severe damage to locals. When facility odors affect air quality and cause citizen complaints, an investigation of those odours may require using standardized scientific methods. Odour intensity is one of the main odour characterization parameter, and represents an important sensory indicator of environmental odours.

Several scientific studies suggest using Odour Emission Factors (OEFs) as a tool for the characterization of the odour emissions and impact prediction of odorous plants, defining these taking into account only the plant capacity for the quantification of the "activity index". The research presents the results of the study of a large Anaerobic-Aerobic integrated Treatment Plant (AATP) located in a sensitive area of the municipality of Salerno (southern Italy, Campania Region), identifying the principal odour sources and their characterization in terms of odour concentration and emissions by dynamic olfactometry. OEFs relevant to single-process steps are estimated using the experimental data set as well as compared with the theoretical ones proposed in literature studies on similar treatment facilities. SOEFs (Specific Odour Emission Factors) for the studied AATP are proposed for one unit, calculating them by taking into account specific real observed parameters of the phase. The results show how the major odour emissions of a AATP are associated to the composting process. OEFs calculated as a function of the plant capacity or with other specific factors (SOEFs) show different values.

Odour emissions from liquid waste treatment plants (LWTPs) generally cause significant effects on the environment in terms of nuisance to exposed population. The particular and complex nature of the mixture of the volatile substances, its variability in time and the strong influence of the atmospheric conditions, are the elements that delayed their regulation and relative management.