Submitted to: Water Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/15/2002
Publication Date: 10/1/2002
Citation: Kim, H., Murtry, S., McConnell, L.L., Peot, C., Ramirez, M., Strawn, M. 2002. Characterization of wastewater and solids odors using solid phase microextraction at a large wastewater treatment plant. Water Science and Technology. 46(10):9-16. Interpretive Summary: The recently developed method using SPME has been applied to the analysis of odorous gases from wastewater, sludge and biosolids. In comparison to traditional methods, e.g., olfactometry, this method was considerably more convenient and inexpensive. The method can be used to capture odorous compounds on-site and has the potential for continuously monitoring with automatic sampler for SPME. SPME was able to absorb both low molecular weight odorous compounds such as carbon disulfide and heavier compounds such as dimethyl mono and disulfide. The heavier compounds were found to increase in intensity as the solids content of the waste flow increased. Gravity thickeners were the major generators of volatile fatty acids, resulting in lowering of pH. TMA was released only from lime-amended biosolids. The extremely high pH and temperature that resulted from the lime addition to the biosolids appears to have caused the release of TMA. It should be emphasized that much more study is needed under different pH, ORP, temperature and flow conditions to effectively predict the character of gases released from the WWTP unit processes. Studies of aged biosolids are also needed to determine the most persistent odorous chemicals released over time to limit odor complaints from land application sites.
Technical Abstract: A simple and reliable technique has been developed and used to detect odorous gases, i.e., propionic and butyric acids, carbon disulfide, dimethyl sulfide, dimethyl disulfide, and trimethylamine, emitted from various materials generated by the wastewater treatment process. The method detection limits are in the low ppb range and comparable to the odor threshold for human detection. In this study solid phase microextraction (SPME) was employed to characterize and quantify odorous compounds in the headspace over samples collected from various unit processes at the District of Columbia Wastewater Treatment Plant, Washington DC, USA. The patterns of odorous chemicals released from wastewater influent, thickened sludge, dewatered sludge and biosolids were evaluated. Volatile reduced sulfurs were more prevalent in samples collected from downstream processes and corresponded with decreased oxidation-reduction potential (ORP) conditions. Volatile fatty acids were consistently identified in the primary gravity thickeners, while trimethylamine could only be detected from biosolids after the post-liming process.