Dynamics of Volatile Sulfur Compounds and Volatile Organic Compounds in Sewer Headspace Air

Abstract

A 2-year monitoring study was conducted at a sewer pumping station to investigate volatile sulfur compound (VSC) and volatile organic compound (VOC) emission dynamics over a range of timescales to gain an understanding of how they impact the design and execution of sewer odorant monitoring. It is demonstrated that the sewer system was highly dynamic and influenced by a range of processes at different time scales. Based upon odor activity values, hydrogen sulfide and methyl mercaptan had strong potential to be odorous, while dimethyl sulfide and dimethyl disulfide were potentially odorous at source concentrations. In general, VOCs were not likely to be odorous at source concentrations, although some episodic elevations in aromatic hydrocarbon and terpene concentrations to potentially odorous levels were observed and as a result VSCs are the primary targets for sewer odor abatement. A strong diurnal emission cycle was observed, with dynamic ranges (ratio of peak to average concentration) between 2.34 and 4.55 for specific VSCs and 1.82 to 10.6 for specific VOCs. Interday variability over a 1-week period was relatively low for many VSCs, with coefficients of variance generally ranging from 11 to 30%, while VOC emissions had greater variability, with coefficients of variance ranging from 29 to 220%.