Investigation and Assessment of Sludge Pre-treatment Processes


Johannes A. Müller 1,2) , Anke Winter 1) , Georg Strünkmann 2)

1) Institute of Sanitary and Environmental Engineering and 2) Institute of Mechanical Process Engineering, Post Box 3329, Technical University of Braunschweig, D-38023 Braunschweig, Germany, Tel. +49/531/391-7943, Fax +49/531/391-7947, E-mail:



Abstract: The pre-treatment of sludges by disintegration will result in a number of changes in sludge properties. Floc destruction as well as cell disintegration will occur. This leads to an increase of soluble substances and fine particles. Furthermore, biochemical reactions may appear during or immediately after disintegration.

The influence of disintegration of excess sludge on anaerobic digestion was studied in full scale. A stirred ball mill, an ultrasound disintegrator, a lysate centrifuge and an ozone treatment were used. The results of the degradation process was compared to a reference system without pre-treatment. An enhancement of the degree of degradation of 7,4% to 20% was observed. The pollution of sludge water as well as the dewatering properties of the digested sludge were investigated. COD and ammonia in the sludge water were increased and a higher polymer demand was observed while the solid content after dewatering stayed almost unchanged.

Based on these results the cost effectiveness has been assessed taking into account different conditions (size of WWTP, cost for disposal etc.). Capital and energy costs are the main factors while the decrease in disposal costs due to the reduced amount of sludge is the main profit factor.


Key Words: sewage sludge, pre-treatment, disintegration, economic efficiency

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Source: Johannes A. Müller, Anke Winter, Georg Strünkmann (2003). Investigation and Assessment of Sludge Pre-treatment Processes, IWA Specialist Conference Biosolids 2003 - Wastewater Sludge as a Resource, Trondheim, Norway, 23-25 June 2003, 137-144