Proceedings of 13th World Congress on Anaerobic Digestion pages:1-4
World Congress on Anaerobic Digestion edition:13 location:Santiago de Compostela, Spain date:25-28 June 2013
Anaerobic digestion is a well-known technique for the recovery of energy from waste activated sludge. To increase the biodegradability of the sludge and to enhance the digestion efficiency, pretreatment methods are of great importance. In this study, ultrasound and microwave pre-treatment were compared, through the use of three pilot scale semi-continuous digesters with a solids retention time of 20 days. During the experiment, one reactor was fed with untreated sludge (blank), one with ultrasound pre-treated sludge and one with microwave pre-treated sludge (both treated with a specific energy of 2100 kJ/kg sludge). (Organic) dry matter, COD, carbohydrates and proteins were analysed during digestion. The solubilisation of the organic material was the most effective by the ultrasound pre-treatment. The biogas production, which is the result of a change in sludge composition, is the highest in the microwave pre-treated digester. This results in an increased biogas production of 27% (i.e. 0.105 L/g ODS, blank 0.085 L/g ODS), compared to a 23% (i.e. 0.108 L/g ODS) increase by the ultrasound pre-treated digester. From the energy balance it is clear that both pre-treatments are economically not feasible.