Abstract

Batch settling tests are considered in order to obtain dewatering material properties of suspensions/sludges towards the low end of the range of solids fractions. Plausible functional forms are considered for fitting batch settling test (height vs. time) data. In particular, power law and exponential decay functions are shown to be reasonable fits to simulated synthetic batch settling data. These forms are subsequently employed to reconstruct functional relationships between a settling flux function and suspension solids fraction. The functional relationships so obtained are found to be faithful representations of the flux function used to generate the simulated settling data, with improved agreement being achieved by restricting the interval of solids fraction across which the reconstruction is performed. The results suggest that general features only (and not fine details) of batch settling curves are required to reconstruct settling flux functions. In the particular case where power law fits are employed to describe the settling height data, an analytic formula can be derived linking the settling flux function explicitly and directly to the power law fitting parameters. This simplifies immensely the technique for extracting parameters for the settling flux. When applied to real experimental data, errors arising from using the power law fits tend to be small compared to those inherent in the experimental measurements themselves. (C) 2007 Elsevier Ltd. All rights reserved.