G. Lehne, J. A. Müller and J. Schwedes
Institute of Mechanical
Process Engineering, Technical University of Braunschweig,
Post Box 3329, D-38023 Braunschweig, Germany
Abstract:
The mechanical disintegration
can be used for an accelerated and improved anaerobic digestion of excess
sludge. Mechanical disintegration can be used to disrupt the cell walls and to
cause the release of the organic material from the cells. Particle size
analysis describes the size reduction but is not suitable for characterising
the release of the organic material and the cell disruption. Two biochemical
methods were developed for these phenomena.
An ultrasonic homogenizer, a
high pressure homogenizer and stirred ball mills were used for disintegration
experiments using various parameters. Investigations had to detect the
influence of the solid content on the disintegration results. For sludge with a
higher solid content better results in terms of energy consumption could be
achieved. An optimum of the bead diameter and the stress intensity in stirred
ball mills could be detected. A comparison of the results of different methods
of sludge disintegration shows that the investigated ultrasonic homogenizers
are inferior to a high pressure homogenizer and a stirred ball mill in terms of
energy consumption.
The hydrolysis is the
limiting step of excess sludge digestion. For disintegrated excess sludge an
improved and accelerated anaerobic digestion could be detected. The digestion
process is characterised through higher degrees of degradation with increasing
degree of disintegration. For batch and continuous experiments the degree of
degradation could be improved. A combination of mechanical disintegration,
short hydraulic retention times and an immobilisation of the biomass showed
more than doubled degrees of degradation in comparison to untreated sludge.
Keywords:
anaerobic digestion, cell-disruption, disintegration devices, excess
sludge, mechanical disintegration
Origin:
G. Lehne, J. Müller, J.
Schwedes (1999). Mechanical Disintegration and Anaerobic Digestion of
Excess Sludge, IAWQ Conference on Disposal and Utilisation of Sewage Sludge, October
1999, Athens, Greece, pp. 137-144