Comparative investigation of parameters for determining the dewaterability of activated sludge.

This paper compared four parameters evaluating the dewaterability of sludge--capillary suction time (CST), specific resistance to filtration (SRF), bound water content, and dry solids content in the centrifuged sludge cake of the different sludge flocs from seven full-scale wastewater treatment plants. The dry solids content correlated with the normalized CST (R2 = 0.7112, p = 0.003), SRF (R2 = 0.6043, p = 0.011), and the bound water content (R2 = 0.8106, p = 0.001). The normalized CST was correlated significantly with SRF (R2 = 0.9450, p = 0.000) and correlated with the bound water (R2 = 0.5110, p = 0.0417). However, SRF correlated very weakly with the bound water (R2 = 0.3929, p = 0.0448). It is not necessary to use both CST and SRF at the same time to estimate the sludge dewaterability. The normalized CST is feasible because of its affordability, simple equipment, and measurement procedure. However, another parameter indicating the dewatering extent, such as dry solids content in sludge cake, should be applied together to evaluate the dewatering efficiency of the activated sludge.