Heavy metal-affected degradation of butyric acid in anaerobic digestion

The accumulation of both forms of butyric acid (HBu) has been used as an indicator of digester failure. However, the present experimental results indicated that the normal- and iso- HBu-degradation activities of the methanogens increase by 14–25% and 17–43%, respectively, for each gram of the biomass coming into contact with 0•02–3•89 mg of Mn, Zn, Ni, Fe and Cu. These results imply that in the presence of these heavy metals care should be taken in using HBu accumulation as an indicator of digester failure.