Developments and Applications of sludge pretreatment Processes


J. A. Müller


Institute of Sanitary Engineering and Institute of Mechanical Process Engineering,
Technical University of Braunschweig, Post Box 3329, D-38023 Braunschweig, Germany


Pre-treatment processes are widely investigated in order to improve the wastewater treatment or sludge management. This paper will summarise the various approaches that have been carried out in sewage sludge pretreatment so far and will focus on new disintegration methods that are in the process of investigation. Pre-treatment processes have been developed in order to improve subsequent sludge treatment and disposal. Disintegration of sludge solids in the aqueous phase changes the sludge structure and solubilizes organic matter. Applied disintegration techniques such as mechanical, thermal, chemical and biological methods are briefly described. The methods are compared regarding energy consumption, operational reliability and stage of development for application on wastewater treatment plants. Mechanical and thermal methods appear to be most suitable at this stage. The effects of pre-treatment on subsequent sludge treatment processes and the wastewater treatment are described. The performance of various methods is assessed. For the improvement of stabilization, mechanical and ozone treatment as well as thermal treatment perform best. Dewatering can be enhanced by thermal and freeze/thaw treatment. All methods show positive effects in the reduction of the number of pathogens. Pre-treatment leads to secondary effects like the generation of recalcitrant compounds and odor, which is mainly a problem of thermal and ozone treatment. The evaluation of capital and operational costs is difficult, because of the lack of full scale experience. Especially thermal, freeze/thaw and biological treatments can be realized at low costs if the conditions are appropriate. Nevertheless, the economic efficiency has to be investigated critically for each individual application.




pre-treatment, disintegration, biodegradability, dewatering, sludge handling and disposal




WEFTEC 2001, 74th Annual Conference & Exposition, Atlanta, USA, October 13-17, 2001