An Evaluation of Masking Nuisance Odors from a Source by Chemical and Sensory Analyses

There are many products in the market advertised as masking agents used to overpower strong nuisance odors, such as in or around water resource recovery facilities, solid waste processing facilities, landfills, composting sites, etc. Very little is known about the chemical component of these masking agents because they are protected by trade secrets. This is a problem for the parties involved, as the process of choosing the most adequate agent for the particular odor source falls into guesswork. This paper demonstrates that it is possible to determine how effective the masking product would be before spending time and resources in trials. It proposes to show this by comparing the Weber-Fechner curves of the odor-causing compounds known to be emitted at the facility with the curves from the potential masking agents prepared in the laboratory using an olfactometer. Several sensorial examples show that when the Weber-Fechner curves of the odorants and those of candidate masking agents are compared, it is possible to define the effectiveness of the masking agent tested. This is a novel use of the Weber-Fechner curves. The results show there is direct correlation between what is observed by a panel with real life odor samples subjected to incremental dilution and the Weber-Fechner odor intensity-odor concentration curve interaction between the odorants involved. Future work characterizing additional potential masking compounds by Weber-Fechner accompanied by odor profiling with dynamic olfactometry should shed light on the definitive effectiveness of this method in predicting masking effects and discovering useful masking compounds.

Development of a diagnostic tool: the wastewater collection network odour wheel

The assessment of nuisance odour problems and the application of an effective odour management programme for the associated industrial activity may be achieved using a representative odour wheel and Odour Profile Analysis methodology. The odour wheel is a very useful tool for conducting odour quality control monitoring and developing a constructive dialogue regarding nuisance odours with the public. Previously, odours from wastewater treatment plant activities have been identified and described with a dedicated odour wheel. The oxidation state of the organic chemicals responsible for a given odour depends on multiple parameters specific to the individual wastewater collection networks (residence time of wastewater, topographic disposition and network slope, aeration and on line chemical treatment processes). This is especially important for odorous nitrogen, sulfur and volatile fatty acids. Trained sensory odour panels combined with chemical analyses have been used to study wastewater collection network odours and to adapt the wastewater odour wheel accordingly. The wastewater collection network odour wheel has been produced using the results of five sampling campaigns; eight out of the 11 odour families constituting the wastewater odour wheel have been identified and consequently validated for sewer networks. Different groups of odours have been perceived according to the presence or absence of wastewater effluents at the various sampling points.

Sensory assessment and characterization of odor nuisance emissions during the composting of wastewater biosolids

Compost plants produce odorous compounds that can cause an "odor nuisance" to neighbors. Methods to evaluate odors exist, but they are not relevant for determining olfactory nuisance. The objectives of this study were to characterize by sensory means the odor nuisance (character and intensity) from composting plants that treat raw biosolids from wastewater plants. Research determined odor character and intensity by the "odor profile method" from raw biosolids, off-gases from the final compost product, and air samples from compost processing. Odor nuisance categories were defined on a "compost odor wheel". Eleven odor categories were determined from a total of 45 observed primary and secondary odor notes: (1) fishy/ammonia; (2) fragrant/fruity; (3) terpene/pine/lemon; (4) solventy/hydrocarbon; (5) grassy/woody/smoky; (6) earthy/musty/moldy; (7) rancid; (8) putrid/dead animal; (9) sweet; (10) sulfur/cabbage/garlic; and (11) fecal/sewery. The odor profile method and the compost odor wheel are suggested as a way to define odor nuisance from a compost plant.

Effectiveness of masking agents: outcome of a three-year study at pilot and full scales

Commercial products used as masking or neutralizing agents against odour emissions from solid waste activities were investigated both at pilot scale and at three full scale sites. Twenty-six products were first characterized and classified as potential masking or neutralizing agents. Four of the products tested at pilot scale revealed a masking efficiency and a significant decrease of the discomfort index. No evidence of neutralization effect was observed during the field tests.

Characterisation of odour masking agents often used in the solid waste industry for odour abatement

Odours from waste management facilities, wastewater treatment plants and composting areas have become a major nuisance issue for operators. In addition to facing regulations which tend to become more stringent, operators are also facing increased public pressure due to complaints from neighbours resulting in the temporary shutdown of such plants, therefore the elimination of atmospheric odours is becoming a major industrial objective. Many commercial odour control products are available on the market, however, very little is known concerning their real efficiency and mechanism of action. This paper will present the results from the study of 19 agents collected in various countries. The products were first characterised both in terms of their chemical composition and sensory properties. Selected products with different modes of application were then submitted to a study of their efficiency at the pilot-scale level. The results from one product test showed no significant difference in their odour removal efficiency as determined by olfactory and chemical analysis of the emission before and after application of the odour control product.

Analysis of drugs and personal care products in French source and drinking waters: the analytical challenge and examples of application

This paper illustrates the challenge faced by analytical chemists when trying to measure selected compounds representative of various classes of prescription and hospital drugs. Because hundreds of drugs belonging to a wide variety of chemical groups are allowed for use, an array of analytical methods has to be implemented. As an example, as part of the European Poseidon Project, five different methods were required to measure eight drugs and personal care products. These methods are discussed in detail. Examples of application to surface and ground waters from the Paris area are also reported. The antibiotics roxithromycin and sulfamethoxazole were detected for the first time in the Seine River downstream of Paris. The behaviour of the eight target compounds during aquifer recharge and drinking water treatment is described. An incident involving the detection of micrograms per litre levels of the personal care product Galaxolide in a drinking water distribution system is reported. The value of the pharmaceuticals and personal care products selected as potential indicators is also discussed.