Effects of addition of soluble oxidants on the thermophilic anaerobic digestion of biomass to methane

Bioconversion of polymeric substrates in anaerobic digesters is slow. Exploratory research was conducted on the effects of the addition of soluble oxidants to a thermophilic, anaerobic, semicontinuous stirred tank reactor (CSTR) fed a biomass feedstock. After adaptation, added nitrate was quantitatively reduced to ammonia and isotope-labelling experiments confirmed that denitrification reactions did not occur. Addition of sulfate to a continuous nitrate amended digester resulted in sulfate accumulation, whereas sulfate addition to nonnitrate-amended digesters resulted in sulfate reduction. These results support the hypothesis that nitrate is preferentially reduced in the presence of sulfate and nitrate.