Biodegradation of potato slops from a rural distillery by thermophilic aerobic bacteria

A study has been made of thermophilic aerobic biodegradation of the liquid fraction of potato slops (distillation residue) from a rural distillery. The COD of this fraction ranged from 49 to 104 g O2/l, the main contributions to the COD coming from organic acids, reducing substances, and glycerol. It was found that biodegradation could be divided into the following stages: organic acids were removed first, followed by reducing substances and glycerol. The extent of removal varied according to the process temperature. At 50 °C, acetic and malic acids were removed completely, but the amount of isobutyric acid increased. At 60 °C, organic acid removal ranged from 51.2% (isobutyric acid) to 99.6% (lactic acid). Removals of glycerol and reducing substances were 86.2% and 87.4%, respectively. COD reduction was also temperature dependent, the highest removal efficiency (76.7%) being achieved at 60 °C. Dissolved oxygen may have limited the biodegradation process, as indicated by the DOT-versus-time profile.