Thermophilic and hyper-thermophilic co-digestion of waste activated sludge and fat, oil and grease: Evaluating and modeling methane production

Renewable energy and clean environment are two crucial requirements for our modern world. Low cost, energy production and limited environmental impact make anaerobic digestion (AD) a promising technology for stabilizing organic waste and in particular, sewage waste. The anaerobic co-digestion of thickened waste activated sludge (TWAS) and sewage treatment plant trapped fat, oil and grease (FOG) using different FOG-TWAS mixtures (20, 40, 60 and 80% of FOG based on total volatile solids (TVS)) were investigated in this study using both thermophilic (55 +/- 1 degrees C) and two stages hyper-thermophilic/thermophilic (70 +/- 1 degrees C and 55 +/- 1 degrees C) anaerobic co-digestion. The hyper-thermophilic co-digestion approach as a part of the co-digestion process has been shown to be very useful in improving the methane production. During hyper-thermophilic biochemical methane potential (BMP) assay testing the sample with 60% FOG (based on TVS) has been shown to significantly increase the maximum methane production to 673.1 +/- 14.0 ml of methane as compared to 316.4 +/- 143 ml of methane for the control sample. This represents a 112.7% increase in methane production compared to the control sample considered in this paper. These results signify the importance of hyper-thermophilic digestion to the co-digestion of TWAS-FOG field. (C) 2016 Elsevier Ltd. All rights reserved.