Conditioning,
Thickening and Dewatering of Mechanically disintegrated EXCESS sludge
Johannes A. Müller
Institute of Mechanical Process Engineering
and Institute of Sanitary Engineering , Technical University of Braunschweig,
Germany
Conclusions
The
influence of mechanical disintegration of excess sewage sludge on the
performance of centrifugal dewatering and filtration was investigated.
Examining different methods of mechanical cell disintegration the best results
were obtained using a high-pressure homogenizer. As a result of disintegration
the dry solids content of the dewatered sludge increases when applying
centrifugal forces. In the case of unconditioned sludge separated by using a
beaker centrifuge this can be explained by the large portion of organic
components which can be found in the centrate, whereas a high degree of the
inorganic components can be found in the sediment. By adding conditioning agents the organic components
are flocculated while the disruption of the particle structure leads to an
increase in conditioner-demand. A dual conditioning using ferric salts and
polymer led to the lowest dosage and the best dewatering results. Thickening
results (using a decanter) are improved for disintegrated sludge what may be
caused by a different floc structure. Sludge flocs created from smaller sludge
particles and a higher amount of flocculation agent lead to better thickening
properties. Dewatering results (using a membrane plate and frame filter) were
deteriorated due to the disintegration. Improved dewatering results obtained in
a high pressure filter press show a potential improvement by disintegration,
but not for commercially available dewatering equipment. In industrial
application disintegration shows some positive effect on thickening of excess
sludge, while the dewatering results are deteriorated. The disintegration of
cells presents a opportunity to reduce the waste solid but there are still
challenges to achieve effective dewatering with existing industrial
technologies.
Keywords:
mechanical disintegration, cell-disruption,
dewaterability, excess sludge, conditioning
Source: J. A. Müller (2003). Conditioning, Thickening and Dewatering of Mechanically Disintegrated Excess Sludge, Separation Science and Technology, 38(2003)4, 889-901