Pre-treatment of thickenedwaste activated sludge (TWAS) for enhanced biogas production via the application of a novel radial horn sonication technology

The efficacy of sonication as a pre-treatment to anaerobic digestion (AD) was evaluated in terms of solubilization dewaterability and AD performance using thickened waste activated sludge (TWAS). Eighteen experimental conditions were evaluated at low frequency (20 kHz) duration (2-10 s) amplitude (approximately equal to 8-12 μm) and applied pressure (0.5-3.0 barg) using a sonix™ patented Ti sonoprobe capable of delivering an instantaneous power of approximately equal to 6 kW. An optimized experimental protocol was applied as a pretreatment for biochemical methane potential (BMP) testing and semi-continuous trials. The results showed that the sonix™ technology delivered effective sonication at very short retention times compared to conventional system by effectively disrupting the floc structures and filaments within the TWAS causing an increase in solubilization and fine readily digestible material. Both BMP tests and semi-continuous trials demonstrated that sonicated TWAS yielded higher biodegradability and CH₄ potential compared to untreated TWAS. Partial-stream sonication (30:70 sonicated to untreated TWAS) led to a proportionate increase in biogas production illustrating the benefits of full-stream sonication.