The Use of Chemical Sensors to Monitor Odour Emissions at Municipal Waste Biogas Plants

Municipal waste treatment plants are an important element of the urban area infrastructure, but also, they are a potential source of odour nuisance. Odour impact from municipal waste processing plants raises social concerns regarding the well-being of employees operating the plants and residents of nearby areas. Chemical methods involve the determination of the quantitative composition of compounds comprising odour. These methods are less costly than olfactometry, and their efficiency is not dependent on human response. The relationship between the concentration of a single odorant and its odour threshold (OT) is determined by the odour activity value (OAV) parameter. The research involved the application of a multi-gas detector, MultiRae Pro. Measurements by means of the device were conducted at three municipal waste biogas plants located in Poland. In this paper we describe the results obtained when using a detector during the technological processes, the unitary procedures conducted at the plants, and the technological regime. The determination of these relationships could be useful in the development of odour nuisance minimization procedures at treatment plants and the adjustment to them. This is of paramount importance from the viewpoint of the safety and hygiene of the employees operating the installations and the comfort of residents in the areas surrounding biogas plants. Monitoring of expressed odorant emissions allows the course of technological processes and conducted unit operations to be controlled.

The effect of short-term storage temperature on the key headspace volatile compounds observed in Canadian faba bean flour

The odour emitted from the high-tannin fab bean flour ( Vicia faba var. minor), was characterized by headspace solid-phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC–MS). The relative odour activity value (ROAV) was used to monitor the changes in key volatile compounds in the flour during short-term storage at different temperature conditions. The key flavour compounds of freshly milled flour included hexanal, octanal, nonanal, decanal, 3-methylbutanal, phenyl acetaldehyde, (E)-2-nonenal, 1-hexanol, phenyl ethyl alcohol, 1-octen-3-ol, β-linalool, acetic acid, octanoic acid, and 3-methylbutyric acid; these are oxidative degradation products of unsaturated fatty acids and amino acids. Despite the low lipid content of faba beans, the abundances of aldehydes arising during room temperature storage greatly contributed to the flavour of the flour due to their very low odour thresholds. Two of the key volatiles responsible for beany flavour in flour (hexanal, nonanal) increased greatly after 2 weeks of storage at room temperature or under refrigerated conditions. These volatile oxidation products may arise as a result of enzymatic activity on unsaturated fatty acids, and was seen to be arrested by freezing the flour.

DEVELOPING A TECHNOLOGY OF LOCAL WINES WITH THE ENHANCED AROMATIC PROFILE

Different methods of enhancing the aromatic profile of wines are researched throughout the world. One of them consists in adding unsaturated fatty acids to must as the yeast feeding. This work considers how the aromatic profile of dry white table wine made from the local grape variety Aromatny is influenced by the feeding that contains olive oil (a source of oleic acid) and the enzyme lipase and is added to must in combination with rehydrated active dry yeast Anchor Alchemy I (the species Saccharomyces cerevisiae). This method has been compared with the two other ones: with the classic method of obtaining dry white table wines by must fermentation (control) and with the sur lie method (when the dry white table wine material is aged on the lees for three months following the end of the must fermentation process). In the wines under study, 19 volatile compounds have been identified and quantified. These compounds, which are the most noticeable and active agents in aroma formation, include higher alcohols, organic acids, complex esters, aldehydes, terpene alcohols. The sample where the feeding was added is substantially higher in aroma-forming compounds than the other samples are. Also, this sample has the highest odour activity value (OAV). Sensory analysis of the wines considered has shown that the feeding containing olive oil and lipase has a positive effect on the aromatic profile of wine: in the aroma, there are distinct floral and fruity notes, more intense than those in the control sample an in the one obtained by ageing the wine material sur lie. This is possible due to a higher concentration of complex esters and a moderate content of higher alcohols. Adding the feeding results in no unpleasant tones in the wine’s odour, which are often caused by fatty acids, as their content is low. The advantages of the method suggested to enhance the aromatic profile of wines are its simple production technology and availability of the natural ingredients of the feeding. This research is supposed to help wine manufacturers satisfy consumers’ demand for local wines with their site-specific character, because one of the main motivations for tourists to visit the world’s wine-producing regions is an opportunity to taste unique wines with a pronounced and attractive floral-fruity aroma

Evaluation of Perceptual Interactions between Ester Aroma Components in Langjiu by GC-MS, GC-O, Sensory Analysis, and Vector Model

The volatile compounds of three Langjiu (“Honghualangshi, HHL”, “Zhenpinlang, ZPL”, and “Langpailangjiu, LPLJ”) were studied by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). The results showed that a total of 31, 30, and 30 ester compounds making a contribution to aroma were present in the HHL, ZPL, and LPLJ samples, respectively. From these esters, 16 compounds were identified as important odour substances, and their odour activity values (OAVs) were greater than 1. The key ester components were selected as: ethyl acetate, ethyl 2-methylbutyrate, ethyl 3-methyl butyrate, ethyl hexanoate, and ethyl phenylacetate by aroma extract dilution analysis (AEDA), odour activity value (OAV), and omission testing. Five esters were studied for perceptual interactions while using Feller’s additive model, OAV, and a vector model. Among these mixtures, they all have an enhancing or synergistic effect. Among these mixtures, one mixture presented an additive effect and nine mixtures showed a synergistic effect.

Characterization and prediction of odours from municipal sewage treatment plant

One of the causes of public discomfort and complaint about odour in China is the nuisance odour, generated from the municipal sewage treatment plants. With the ability to be dispersed over a long distance, the odours can affect a large number of people. With the aim of identifying the compounds contributing the most to the overall odour emanating from municipal sewage treatment plant, and developing a prediction model for sensory odour concentration based on the compound odour activity value (OAV), odour samples from 2 days were collected at a municipal sewage treatment plant in Tianjin in the months of October and November 2013. Odour concentrations (OCs) were measured by the triangular odour bag method. Chemical components were quantified by gas chromatography–mass spectrometry. According to the analysis of odour emission characteristics, it was found that hydrogen sulfide and methyl mercaptan were the key odorants responsible for the overall odour. To understand the interrelationship of these two odorants, 10 groups of a binary mixture of hydrogen sulfide and methyl mercaptan, representing different levels of odour concentration and intensity, were prepared in the laboratory. OCs were regressed against OAV using multivariate linear regression. A statistically significant positive correlation was found between single-compound OAV and odour concentration (by both SPSS and Minitab software). Furthermore, the models were validated by field monitoring data, which showed the odour prediction concentration had a good fit to the measured concentration by using Minitab software. Lastly, the Austal 2000 model system was used for the simulation of the odour emission dispersion into the surrounding area. This study provides an effective way to predict the odour emission condition in municipal sewage treatment plant.

Technical note: Characterization of key volatile odorants in rabbit meat using gas chromatography mass spectrometry with simultaneous distillation extraction

<p>This study explored the key volatile compounds in both male and female rabbit meat. Simultaneous distillation extraction with dichloromethane was adopted to extract the volatile compounds in Hyla rabbit meat. A total of 35 volatile compounds were identified by gas chromatography–mass spectrometry and quantified with 2, 4, 6-thimethylpyridine as internal standard. Seventeen volatile aldehydes, 4 alcohols, 2 ketones, 2 acids, 1 heterocyclic compound, 2 alkanes and 7 esters were detected. Hexanal, heptanal, octanal, nonanal, (E, E)-2, 4-decadienal, 1-octen-3-ol and (Z)-2-decenal were the key odorant compounds, with high relative odour activity value. Furthermore, the concentration of volatile compounds in male rabbit meat was higher than that in female rabbit meat.</p>