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Water Science & Technology Vol 42 No 9 pp 73–80 © IWA Publishing 2000

Enhancement of anaerobic sludge digestion by ultrasonic disintegration

U Neis*, K Nickel** and A Tiehm***

* Department of Sanitary Engineering, Technical University of Hamburg-Harburg, 21071 Hamburg, Germany
** Department of Sanitary Engineering, Technical University of Hamburg-Harburg, 21071 Hamburg, Germany
*** Department of Sanitary Engineering, Technical University of Hamburg-Harburg, 21071 Hamburg, Germany


ABSTRACT
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.

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