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 non-desirable 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. In addition, 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.