Molecular weight distribution of pretreated thickened waste activated sludge and fat, oil, and grease Rania Mona Alqaralleh, Kevin Kennedy, & Robert Delatolla Environmental Science and Pollution Research, Feb. 2020 Abstract: Co-digestion samples containing thickened waste activated sludge and fat, oil and grease were subjected to three different pretreatment methods, i.e., microwave at 175 °C, hyper-thermophilic stage at 70 °C, and conventional heat at 70 °C. The soluble matter extracted from the un-pretreated and pretreated samples were subjected to an ultrafiltration (UF) process using four different membrane sizes (300, 100, 10, and 1 kDa) for molecular weight distribution analysis. Every pretreatment method had a different effect on the solubilization and redistribution of the soluble matter (SCOD and TVFA). For example while MW pretreatment resulted in a significant increase in the SCOD at the lowest molecular weight (< 1 kDa) and at the highest molecular weight (>300 kDa), Hyper pretreatment caused the majority of the SCOD ( 62.7% of total SCOD) to be concentrated at the smaller molecular weight range (< 10 kDa). The MW and hyper-thermophilic pretreatments were much more effective in increasing samples solubilization and biogas production compared to the conventional heat pretreatment. The hyper thermophilic samples had the maximum improvement in cumulative biogas production from all the molecular weights compared to MW-and Heat-pretreated samples; Hyper-pretreated samples achieved 86.5% higher cumulative biogas production compared to the control.