Odor control during post-digestion processing of biosolids through bioaugmentation of anaerobic digestion

The effects of bioaugmenting anaerobic biosolids digestion with a commercial product that contained selected strains of bacteria from genera Bacillus, Pseudomonas, and Actinomycetes, along with ancillary organic compounds containing various micronutrients were evaluated. The main objective of the study was to investigate the effects of bioaugmentation specifically on the performance of methanogenesis during anaerobic digestion, as well as on the generation and fate of odor-causing compounds during the storage of the digested biosolids. The bench-scale digester with 5 g/L bioaugment generated 29% more net CH₄ than a control during the eight weeks of operation. In addition, the average residual propionic acid concentration in the bioaugmented digester was 46% lower than that in the control. The biosolids digested in the bioaugmented digester generated a negligible amount of methyl mercaptan (CH₃SH) during 10 days of post-digestion storage, while CH₃SH concentration in the control reached nearly 300 ppmv during the same period. Similarly peak dimethyl sulfide (CH₃SCH₃) generated by stored biosolids from the bioaugmented digester was only 37% of that from the control. Similar results were obtained in a subsequent short term study designed to confirm the repeatability of the findings.