Mitigation of Odors from Lime Stabilized Biosolids

The Blue Plains WWTP, in Washington, DC, relies on land application for about 85% of their biosolids. Therefore, it is essential to obtain a properly stabilized Class B product that is largely odor-free. This poster will discuss the odorous compounds released from biosolids and the in-plant (on-site) conditions that promote odorous biosolids products. Controls for odor reduction and methods for implementation will be presented.The breakdown of cationic polymers used in thickening and dewatering produces compounds called trimethyl amines (TMAs), which are associated with an organic, “fishy” odor. The data from this study indicates that TMA production increases with an increase in polymer dose. The amine production appears to also increase with an increase in storage time. The presence of these odors in the control as well as the dosed samples suggests that alternative polymers or conditioning regimes need to be evaluated for thickening or dewatering, such as the use of ferric chloride.Additional data indicated that anaerobic storage of unstabilized liquid sludge prior to lime stabilization resulted in an odorous end product. Lime stabilization prevents further adverse biological activity from occurring, but does not alter the odor characteristics of an already odorous product.The optimum lime dose required is affected by blending and proper incorporation of lime into the biosolids, as well as the anticipated storage time. An increase in storage time or a decrease in lime dose promotes biological activity and the increased production of odorous compounds. For this study dimethyl disulfide production peaked after 7 days, while methyl mercaptan and dimethyl sulfide continued to be produced. The biosolids product with a 15% lime dose produced substantial odors that increased over time. The 30% and 40% limed biosolids products were very stable, and the odors actually appeared to decrease with increased storage. At Blue Plains WWTP, a lime dose of at least 20–25% may be required to achieve a stabilized product with low off-site odors. If storage is anticipated, the lime dose may need to be increased to 30%.