Supplementary In-Depth Analysis of the Waste Activated Sludge Dewatering Process Using a Rheological Analysis
Hou‐Feng Wang, Yanan Bai, Wei Zhang, Huajie Wang, Raymond Jianxiong Zeng
Abstract
Much research has been conducted to improve sludge dewaterability and reveal its dewatering process. However, to date, two key issues remain unsolved: (1) the difficulty of dewatering sludge and (2) why suitable chemical conditioning can improve sludge dewaterability. This study is focused on addressing these two problems using a rheological analysis. Flow and dynamic measurements were performed to investigate the rheological properties of three types of sludge samples (raw sludge, acid-conditioned sludge, and Fenton-conditioned sludge) with different dewatering performances and a total solid content (TS) range of 20–62 g/L (2–6.2 wt %). The measured data were fitted to predict the rheological behaviors of the sludge at moderate and high TS values (15–50 wt %). A horizontal analysis and comparison of the rheological characteristics of the sludge samples indicated that rheological properties of the sludge exhibited a strong dependence on the solids content of the raw and treated sludge. An increase in the solids content significantly strengthened the solid-like properties and increased the deformation resistance, causing the sludge to become more resistant to flow and resulting in lower flowability of the sludge system; this provided an explanation for the difficulty in sludge dewatering. A vertical comparison and analysis of the rheological behavior of the sludge samples addressed the second key issue and indicated that a suitable conditioning method such as acid and Fenton oxidation conditioning had positive effects on the evolution of the rheological parameters of the sludge; namely, the conditioning resulted in weaker viscoelastic properties and better flowability. These results provide insights into the fundamental mechanism of sludge dewatering through rheological analysis.