WERF Odor Study Phase III: Effect of Alum Addition on Odorant Production from Anaerobically Digested Biosolids

In recent years, extensive research has been performed to verify and identify offensive odor gases of their production mechanisms during biosolids cake storage prior to land application. It was identified that volatile organic sulfur compounds (VOSCs) including methanethiol (MT), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS) contribute to the offensive odor. The formation of VOSCs was linked to microbial degradation of biomolecules, specifically residual proteins, thus mitigation measures were recommended to reduce the bioavailable portion of proteins in biosolids. In this research, alum (aluminum sulfate) was used as a potential binder to reduce accessibility of soluble proteins in biosolids, thus prevent them from biodegradation. Both laboratory trials and field trials were performed to verify the potential of alum on biosolids odor reduction. The laboratory trial results indicated that alum can effectively reduce biosolids odor, and up to 100% removal of total VOSCs (TVOSCs) was observed at high doses of alum. In a field trial, although not 100% removal, up to 55% peak TVOSCs reduction was observed. In addition, alum also reduced polymer demand required to achieve optimum polymer dose for dewatering which could offset alum costs.