Impact of Fatty Waste on Anaerobic Digestion of Sewage Sludge at a Municipal Wastewater Treatment Plant - A Case Study

Anaerobic digestion is a common method for utilization of sewage sludge at large-scale wastewater treatment plants. This process generates biogas, which is a source of renewable energy. Intensification of biogas production can be achieved, for example, through co-digestion, with fatty waste characterized by a high methane potential (0.85 Nm3/kg VS versus 0.136 Nm3/kg VS for excess sludge). However, due to high lipid content, fatty waste can cause incomplete degradation of organic compounds and accumulation of volatile fatty acids (VFA) in the digester. The purpose of this study is to show the changes in the efficiency of the digestion process at a municipal wastewater treatment plant after feeding digester with fatty waste. Co-fermentation shortened HRT from 27.0 d to 23.7 d. The use of co-digestion had a positive effect on biogas production. Volume of biogas increased from 2750 Nm3/d to 4004 Nm3/d (average). It was noted that the percentage share of organic dry matter in the digested sludge decreased on average from 71.32% to 69.15%.