MESOPHILIC ANAEROBIC DIGESTION WITH HIGH TEMPERATURE MICROWAVE PRETREATMENT

Thickened waste activated sludge (TWAS) was pretreated with a microwave (MW) Accelerated Reaction System to temperatures higher than the boiling point (between 110 and 175°C) by using different MW intensities. The biological methane potential (BMP) test was used to see the impact of high temperature MW pretreatment on biogas production. Although inoculum used in this test was acclimatized for 4 months by TWAS pretreated at 175°C, inhibition was observed during BMP tests. A second set of BMP tests were designed to see the effect of better acclimation on biogas production. This time inoculum was further acclimatized for an additional 3 months. The results showed that better acclimation gives high improvement on biogas production. In the second set of experiments TWAS pretreated at 175°C produced 31 ± 6% more biogas than the control (raw TWAS) at the 18th day of the BMP test whereas the highest improvement observed from the first set of experiments was only 13 ± 1%.