Characterization and Control of Reduced Sulfur Odors from Lime Stabilized and Digested Biosolids

The reduced sulfur odors derived from lime stabilized and digested biosolids were evaluated in this study. It was determined that the reduced sulfur odor compounds emitted from lime stabilized biosolids are typically dimethyl disulfide and dimethyl sulfide. The source conditions for these biosolids odors was found to be due to a combination of upstream conditions during thickening that led to low oxidation-reduction potentials and/or inadequate lime addition and incorporation into the biosolids. These process conditions led to odors during storage of the biosolids. Maintenance of a more positive oxidation-reduction potential coupled with proper lime addition and incorporation into the biosolids are suggested methods to reduce the production of reduced sulfur odors. The main odor compounds emitted from digested biosolids were the family of mercaptan compounds. The source of the odors from digested biosolids is suspected to be from undegraded proteins in the digested biosolids. It was determined that shearing of the biosolids increased the odor production potential. An increase in shear on digested biosolids also increased odor production. Reducing shear on biosolids and more complete degradation of proteins are suggested methods to reduce odor production potential.