Bioaugmenting anaerobic digestion of biosolids with selected strains of Bacillus, Pseudomonas, and Actinomycetes species for increased methanogenesis and odor control

The objective of this study was to evaluate the effects of bioaugmenting anaerobic biosolids digestion with a commercial product containing selected strains of bacteria from genera Bacillus, Pseudomonas, and Actinomycetes, along with ancillary organic compounds containing various micronutrients. Specifically, the effects of the bioaugment in terms of volatile solids destruction and generation and fate of odor-causing compounds during anaerobic digestion and during storage of the digested biosolids were studied. Two bench-scale anaerobic digesters receiving primary and secondary clarifier biosolids from various full-scale biological wastewater treatment plants were operated. One of the digesters received the bioaugment developed by Organica Biotech, while the other was operated as control. The bioaugmented digester generated 29% more net CH₄ during the 8 weeks of operation. In addition, the average residual propionic acid concentration in the bioaugmented digester was 54% of that in the control. The monitoring of two organic sulfide compounds, methyl mercaptan (CH₃SH) and dimethyl sulfide (CH₃SCH₃), clearly demonstrated the beneficial effects of the bioaugmentation in terms of odor control. The biosolids digested in the bioaugmented digester generated a negligible amount of CH₃SH during 10 days of post-digestion storage, while CH₃SH concentration in the control reached nearly 300 ppmv during the same period. Similarly, peak CH₃SCH₃ generated by stored biosolids from the bioaugmented digester was only 37% of that from the control.