Enhancement of anaerobic sludge digestion by ultrasonic disintegration

Biological cell lysis is known to be the rate limiting step of anaerobic sludge stabilization. Shear forces generated by high-power ultrasound can be used to disintegrate bacterial cells in sewage sludge. Thus the quantity of bioavailable dissolved organic substrate (Chemical Oxygen Demand) is significantly increased. As a result the subsequent sludge degradation is accelerated considerably. In our tests the fermentation process of sonicated waste activated sludge remained stable even at a very short digestion time of 4 days. The enhanced degradation rate resulted in a reduced volatile solids concentration of the digested sludges after the usual fermentation times.