Control of Biosolids Cake Odors using the New Biosolids Odor Reduction Selector Process

Recent introduction of more efficient dewatering devices that generate higher solids concentrations in dewatered cake has been plagued with the undesirable side effect of more odorous dewatered biosolids. Previous research has shown that the production of volatile organic sulfur compounds (VOSC's) such as methanethiol (MT), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS) during dewatered biosolids storage is one of the major contributors to nuisance odors from anaerobically digested and dewatered biosolids. This research also indicated the importance of methanogens in the degradation of VOSC's, in which VOSC's increase dramatically if methanogens are inhibited. Methanogenic microorganisms can degrade the VOSC's, and they are the reason that VOSC concentrations begin to decrease after reaching a peak that usually occurs at 7-14 days of cake storage. Research has shown that odor reducing methanogens present in digested biosolids require time to re-acclimate in stored biosolids cake after dewatering. Biological seeding of freshly dewatered biosolids with stored, acclimated biosolids was hypothesized as a means of reducing VOSC's and odors more rapidly in biosolids cake than if the biosolids were stored without additives. A study was performed in order to test this hypothesis. Results from this study showed significantly lower concentrations (greater than 75% reduction of odorous compound concentrations) in as little as 3 days of storage as compared to un-amended fresh biosolids cake, which required 10 days for concentrations of MT and DMS to decline to similar levels.