Characterization of wastewater and solids odors using solid phase microextraction at a large wastewater treatment plant H. Kim* † , S. Murthy**, L.L. McConnell***, C. Peot****, M. Ramirez**** and M. Strawn***** * US Dept. of Agriculture, Agricultural Research Service, Animal Manure and Byproduct Laboratory, Beltsville, MD 20705, USA † Current address: Department of Environmental Engineering, University of Seoul, 90 Chonnong-dong Dongdeamun-gu, Seoul 130–743, Korea (Email: h_kim@uos.ac.kr) ** CH2M HILL, Herndon, VA 20171, USA *** US Dept. of Agriculture, Agricultural Research Service, Environmental Quality Laboratory, Beltsville, MD 20705, USA **** DC Water and Sewer Authority, Washington DC 20032, USA ***** Peer Consultants, Rockville, MD, USA 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. Keywords Biosolids; gas phase analysis; odor; solid phase microextraction; trimethylamine; volatile fatty acids; volatile reduced sulfurs; wastewater Introduction Depending on various operating parameters, each wastewater and sludge unit process can contribute to the release of specific odorous compounds. Individual unit processes can not only contribute to on-site process odor emissions, but they can greatly affect the odor qual- ity of the resulting biosolids. Odor intensity from wastewater processes usually increases as the wastewater or sludge flows downstream since more septic or reduced conditions are often developed (WEF, 1995). Therefore, it is important to maintain conditions that mini- mize odors within a wastewater treatment facility. Typically, odor reduction from unit processes is achieved by collecting the odors and treating them in scrubbers or biofilters. However, this form of treatment is expensive and not always successful. Reduction in odors at the source will not only reduce on-site air quality problems but will also reduce odor emissions from the biosolids produced and distributed for land application. Relatively few studies have been carried out to evaluate and reduce odors from waste- water treatment facilities, although some studies have evaluated odor emissions from live- stock processing and animal manure treatment facilities (Hobbs et al., 1995; Persud et al., 1996). Prior to identifying methods to control odors, however, it is important to have an easy and reliable method to characterize and quantify these volatile, reactive gases, and Water Science and Technology Vol 46 No 10 pp 9–16 © IWA Publishing 2002 9 Downloaded from https://iwaponline.com/wst/article-pdf/46/10/9/425893/9.pdf by guest on 14 November 2018