Pre-Selection of Flocculants by the Separation Analyser Lumifuge 114 - Article at InfoClearinghouse

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This paper (originally presented at the IWA World Water Congress in Berlin, 2001) reports on lab-scale investigations in relation to pre-selection of flocculants for sludge dewatering with decanter centrifuges using the separation analyser Lumifuge 114. Experiments were carried out with sludge samples of different origin and a number of commercial flocculants.
Kinetics of sedimentation and clarification were measured as well as the compression behaviour and shear sensitivity of sludge sediments. Results obtained were compared with CST-measurements and discussed in relation to findings under field conditions. The separation analyser is an efficient tool for the characterization of sludge samples and flocculant optimisation. The development of appropriate methods for sample pre-treatment is essential for getting relevant results for sludge dewatering under practical conditions. Flocculant performance could be estimated by evaluation of stability against intensive shearing, total solids obtained and initial dewaterability of the sludge cake. Results were in good agreement with field results. The beneficial or negative influence of mechanical pre-conditioning of sludges before flocculant addition could only be deduced by experiment. The separation analyser can be used to this end for model investigations. A screening procedure has been developed. Efficient flocculants should produce high residual total solids and good initial compressibility as well. Lab-scale investigations deliver more reliable results if the dynamic behaviour of the sludge under centrifugal acceleration is also investigated. The separation analyser Lumifuge 114 can provide results about the compression behaviour of sludges in the range between 10 and 100 s. So far no other method or device is known which can deliver such results.
The author welcomes related discussion and comments.
Additional information (reference list of publications, different applications of the separation analyser) is available and up-dated at www.AppliedColloidsSurfactants.info and at www.lum-gmbh.de.
A previous paper on the Preprint Archive “Investigations on sludge dewatering with the separation analyser LUMiFuge 114” contains more details on the principle and is related also to sludge characterization, available on the Preprint Archive http://www.sciencedirect.com/preprintarchive Chemistry Preprint Archive, Volume 2002, Issue 10, October 2002, Pages 1-11. For recent results see Filtech2003/wfc9