Ultrasound activated sludge disintegration could positively affect sludge anaerobic digestion. Due to sludge disintegration, organic compounds are transferred from the sludge solids into the aqueous phase resulting in an enhanced biodegradability. Therefore disintegration of sewage sludge is a promising method to enhance anaerobic digestion rates and lead to reduce the volume of sludge digesters. The addition of disintegrated surplus activated sludge and/or foam to the process of sludge anaerobic digestion can lead to markedly better effects of sludge handling at wastewater treatment plants. In the case of disintegrated activated sludge and/or foam addition to the process of anaerobic digestion it is possible to achieve an even twice a higher production of biogas. Here are few examples:

STP Bad Bramstedt, Germany (85,000 PE or 4.49 MGD) First fundamental study on pilot scale by Technical University of Hamburg-Harburg, 3 years, 1997 - 1999 • reduction in digestion time from 20 to 4 days without losses in degradation efficiency • increase in biogas production by a factor of 4 (renewable energy!) • reduction of digested sludge mass of 25%

STP Ahrensburg, Germany (50,000 PE or 2.64 MGD) Preliminary test on pilot-scale by Technical University of Hamburg-Harburg, 6 months, 1999 • increase in VS destruction of 20% • increase in biogas production of 20%

STP Bamberg, Germany (230,000 PE or 12.15 MGD) 1) Preliminary full-scale test, 4 months, 2002 2) Full-scale installation since June 2004 • increase in VS destruction of 30% • increase in biogas production of 30% • avoided the construction of a new anaerobic digester (3,000 m?? vol.)

STP Freising, Germany (130,000 PE or 6.87 MGD) Fundamental full-scale study by University of Armed Forces, Munich, 4 months, 2003 • increase in biogas production of 15% • improved sludge dewatering of 10%

STP Meldorf, Germany (20,000 PE or 1.06 MGD) ( BNR Oxidation Ditch plant ) 1) Preliminary full-scale test, 3 months, 2004 2) Full-scale installation since December 2004 • increase in VS destruction of 25% • increase in biogas production of 25% • no foam or filamentous organisms present in the anaerobic sludge digester

STP Ergolz 2, Switzerland (65,000 PE or 3.43 MGD) Full-scale test, 3 months, 2004 • increase in VS destruction of 15% • increase in biogas production of 25%

STP Beverungen, Germany (50,000 PE or 2.64 MGD) Full-scale test, 3 months, 2004/2005 • increase in VS destruction of 25% • increase in biogas production of 25%

STP Au, Illertissen/Ulm, Germany (70,000 PE or 3.70 MGD) Full-scale test, 3 months, 2004/2005 • increase in VS destruction of 15% • increase in biogas production of 25%

STP Zeist, Netherlands (75,000 PE or 3.96 MGD) Full-scale installation since May 2005 • increase in VS destruction of 25% • increase in biogas production of 25%

STP Kleinsteinbach, Germany (40,000 PE or 2.11 MGD) Full-scale installation since July 2006 • increase in VS destruction of 25% • increase in biogas production of 25%