Factors affecting odor production in Philadelphia Water Department Biosolids
Abstract:A study was performed to examine the factors that affect odor production from volatile sulfur compounds (VSCs) in anaerobically digested biosolids dewatered using centrifuges. The authors hypothesize that the protein within the biosolids cake is the main substrate for VSC production. The study examined the effect of storage time, FeCl3 addition, protein content, cake solids, and centrifuge technology on odor production from the Philadelphia Water Department biosolids. The source biosolids were from two different anaerobic digesters, the NE and SW plants, and cake solids samples were collected after dewatering from a high solids centrifuge and medium solids centrifuge. In addition, a set of cake samples from each biosolids source were collected in which FeCl3 was added prior to polymer addition at a dose of approximately 0.1 lb FeCl3/lb dry solids. The cake samples (15 lb) were stored for 28 days and during that time air samples were taken periodically from the storage vessels for olfactometry analysis and for analytical quantification of VSC concentration. The results showed odor production increased and peaked during approximately the first week of storage and decreased for the remainder of the study. The odors measured by olfactometry were generally associated with dimethyl sulfide and dimethyl disulfide. The cake from the high solids centrifuge produced greater odors than the medium solids centrifuge and this was related to the cake solids since a correlation existed between odor produced and cake solids concentration. In addition, the odor intensity and hedonic tone were correlated to the protein content of the cake. The addition of FeCl3 significantly reduced odors from the SW biosolids samples, however increased odors associated with the NE samples. These contradictory results were explained by the competing reactions associated with Fe addition which include protein sequestration into the cake and binding of sulfur compounds. In addition, the NE samples had a lower amount of protein in the cake compared to the SW samples after the respective FeCl3 additions.
Document Type: Research Article
Publication date: 2002-01-01
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