Comparison between Different Pretreatment Techniques for Enhancement of the Anaerobic Digest ability of Different Waste Streams

We conducted ultrasound, mechanical (depressurization), thermal, combined (chemi-mechanical and thermo-chemical) pretreatments prior to the mesophilic anaerobic digestion of different waste streams (thickened municipal waste activated sludge, hog manure and food waste). A linear correlation (R2 =0.92) between methane yield (mL CH4/g VSSadded) and VSS reduction observed for pretreatment of various organic wastes in our study suggested that the biodegradable organic matters released from the disintegration of volatile solids mainly enhance the methane production, although the degree of disintegration may be different for similar volatile solids removal based on the nature of organic waste and/or pre-treatment technique. Therefore, the biodegradability of the solubilized organic matters would be more important than degree of disintegration for enhanced anaerobic digestion. On the other hand, we observed a similar trend when different pre-treatment techniques were applied, there was no significant improvement of the solids removal efficiency during digestion, although biogas production and overall solids reduction (digestion + pretreatment) was higher compared to the control digester.