The Application of Ultrasound as a Pre-Treatment for Anaerobic Digestion

The sonication of sewage sludge can be used as a pre-treatment to anaerobic digestion. The anaerobic digestion process has the potential to become more efficient through the break-up and solubilisation of solid sludge particles. Here, the performance of anaerobic digestion was compared when fed with unsonicated sludge and sludges sonicated at two different intensities. The tests were run as a series of batch flasks and three 100 litre anaerobic digesters. The data from the batch tests clearly indicated the positive effect on anaerobic digestion through gas production (increase by 15%) and volatile fatty acid production. The data from the anaerobic digesters was less distinct. Little difference was observed between the volumes of gas produced, however there was an increase in methane production, volatile solids reduction and the soluble COD by up to 6%, 5.5% and 15% respectively when a comparison was made between sonicated and unsonicated sludges. However, sonication was observed to have a detrimental effe...