Modelling the Relationship between Sludge Filtration Resistance and Capillary Suction Time

Abstract

This study modeled the relationship between Sludge Filtration Resistance (SFR) and Capillary Suction Time (CST) using the data generated from different concentrations of CaCl2 for SFR and CST empirically using the Equation proposed by Christensen et al. (1993). The main purpose of conducting CST and SRF tests at wastewater treatment plants is to save operating costs by evaluating the optimal dose of the sludge conditioner, known as the dose of coagulant that yields the minimal capillary suction time or resistance to filtration. In order to establish a relationship between the SFR with CST, there is a relatively good correlation between CST and SFR. The results showed that the values of CST decreased with increasing CaCl2 concentration, and a good dewaterability could be obtained at the CaCl2 dosage of 18 g with the corresponding CST of 5.52 s for 20 mm internal cylinder and 30.84 s for 14.5 mm internal cylinder. The results of SFR tests shown decreased with an increase in CaCl2 dosage. The optimal CaCl2 dosage was 18 g and the corresponding SFR was 2.65 × 108 N·s/m5. The results of this study for CST recommend larger diameter cylinder to be used to test heavy sludge because the larger cylinder significantly reduces the variability and the time taken to conduct the CST tests.