Identifying and Controlling Odor in the Municipal Wastewater Environment Phase 1: Literature Search and Review

Non-carcinogenic occupational exposure risk related to foundry emissions: focus on the workers involved in olfactometric assessments

The scope of this work is the evaluation of the non-carcinogenic occupational risk related to foundry emissions, focusing on the category of workers involved in olfactometric assessments. Odor pollution from industrial activities such as foundries is a serious environmental concern. Sensorial techniques (e.g. dynamic olfactometry, EN13725:2003) currently represent the preferred method for odor emission characterization. During olfactometric analyses, human assessors are directly exposed to the odor at increasing concentrations, thus requiring the assessment of the associated exposure risk to guarantee workers' safety. This paper presents an investigation aiming to produce an inventory of compounds emitted from foundries together with their odor thresholds and toxicological limits (TLVs), with the final objective to propose a procedure for ensuring workers' safety during olfactometric analyses. Looking at the database resulting from this study, among the >100 compounds emitted by foundries, 8 have a maximum concentration above their TLV. Among those, ammonia, H₂S, phenol, toluene and trimethylamine, produce an odor stimulus before they reach a toxic concentration, thus not representing a risk for olfactometric workers. Benzene, formaldehyde and SO₂ are identified as the most critical compounds because they may reach toxic concentrations in foundry emissions, and they start being perceived by humans above their TLV. The proposed procedure entails a minimum dilution factor of 27'000 to be applied to odor samples analyzed by olfactometry, which however might result inapplicable in practical cases, thus pointing out the necessity to adopt chemical measurements to investigate specifically the concentration of the most critical compounds identified in this study.

Assessment of the Effects of Wastewater Treatment Plant Modernization by Means of the Field Olfactometry Method

Methodological aspects of odor studies in ex-post analyses for Polish wastewater management facilities were analyzed based on the example of a modernized and enlarged wastewater treatment plant (WWTP) in Mazovia, in the vicinity of the Warsaw agglomeration. It is a mechanical–biological treatment plant with increased efficiency of biogen removal, using activated sludge in the treatment process, with a maximum hydraulic capacity of 60,000 m3/day. Olfactometric research was carried out by means of a method based on identification and characterization of the odor plume emitted from the examined source. This paper presents the results of odor intensity assessment (in sensory examinations according to a 6-stage scale) and odor concentration measurement (using portable field olfactometers) after the completion of the project, and compares them with similar studies conducted before the commencement of the investment. A total of 10 measurement series were carried out before modernization, and 12 after modernization of the WWTP. Odor concentration and intensity were determined, and the current meteorological situation was assessed at the measurement and observation points (receptors) located within the premises (in total 462 points) and around the WWTP (342 points). In each series of measurements on the windward side of the treatment plant, the background of air pollution with odorous substances was marked. The research showed that air flowing into the area of the sewage treatment plant is clean in terms of odor. During the research, basic sources of odor nuisance were identified, and their impact before and after modernization was characterized. The results presented in radar diagrams show changes in the percentage distribution of frequency of occurrence of individual intensity values at receptor points within and outside the area of the treatment plant. After modernization, a significant decrease in the concentration of odor emitted from the sludge dewatering building and sludge containers was determined. The air-tightness of the sewage channel (covered with concrete slabs and sealed) resulted in a significant decrease in the concentration of odor emitted from this source. Waste (in particular, sewage sludge) collected in the emergency waste storage yard was identified as the main source of odor nuisance. The waste, even after modernization, was an emitter of odorous compounds spreading outside the area of the WWTP. Nevertheless, as a result of the investment, the desired effect of reduction of the degree of odor nuisance was achieved.