Disintegration of sewage sludges and influence on anaerobic digestion

The improvement of anaerobic digestion was investigated in an interdiscipli nary research group. Using four different methods of mechanical cell disint egration the influence of the degree of disintegration and the digestion pa rameters on the performance of the anaerobic process was investigated. Anal ytical methods to describe the degree of cell-disruption had to be develope d. The best results were obtained using a stirred ball mill and a high-pres sure homogenizer. As a result of disintegration the degradation is accelera ted and the digestion time can be reduced, especially when using immobilize d micro-organisms. The treatment of digested sludge by ozonization respecti vely by mechanical disintegration led to an improved biodegradability of re sidual organic compounds. In a following second anaerobic process the treat ed sludge reached an even higher degree of degradation. On the other hand t he disruption of the particle structure leads to an increase in polymer-dem and and no improvement in dewatering results. Sludge water, returned to the aeration tanks, is slightly more polluted, especially the concentration of ammonia increases because of the better anaerobic digestion. (C) 1998 IAWQ Published by Elsevier Science Ltd. All rights reserved.