Potential energy production from anaerobic digestion of dairy wastewater

The performance of a pilot-scale upflow anaerobic filter (UFAF) treating a dairy wastewater was studied for a period of 3 months. Results showed that the UFAF system achieved over 85% chemical oxygen demand (COD) and 90% biological oxygen demand (BOD₅) removal efficiencies at an organic loading rate (OLR) of 6 kg COD/m³.d with a hydraulic retention time (HRT) of 20 hours. Percent methane in the biogas produced in the UFAF was found to be in a range of 75%-85% with the corresponding methane yield of 0.32-0.34 m³ CH₄/kg COD removed. The system produced approximately 770 liters CH₄/day. This would maintain all energy requirements of the feed and recirculation pumps and mixing. Approximately 35% of the energy requirement for maintaining the desired temperature of the pilot-scale anaerobic filter column would also be recovered.