Modeling the relationship between capillary suction time and specific resistance to filtration

The capillary suction time (CST) and the specific resistance to filtration (SRF) tests are both commonly used to estimate sludge dewaterability. Both tests are known to be empirically related but the SRF is much more expensive and time consuming compared with the CST test. The aim of this study was therefore to develop a prediction methodology to obtain SRF test results from the data generated by CST tests under different experimental conditions. This study is based on empirical data sets linking CST with SRF. The prediction equations were developed by first estimating filterability from CST values and then relating it with SRF values using regression analyses. The relationships between the results of the CST and SRF tests were best described using an empirical model, which incorporated logarithmic and squared terms to account for the nonlinear relationship between filterability, total suspended solids, and temperature. The findings were statistically significant (p<0.05) and the model satisfied all the statistical assumptions. Therefore, the model can be used to predict SRF from CST values.