Applying rheological analysis to better understand the mechanism of acid conditioning on activated sludge dewatering.

The pH value is a key parameter and affects sludge dewatering. Comprehensive understanding of the effects and mechanism of pH is important for sludge treatment process and sludge dewatering. The goal of this study was to evaluate the proposed mechanism of acid conditioning on sludge dewatering based on rheological analysis. At lower sludge pH, changes in floc structure, surface properties, and flocculation improved the performance of dewatering. Additionally, lower sludge pH caused the hydrolysis of EPS and intracellular materials, which released greater amounts of bound water. These changes resulted in altered rheological properties, weakening network strength and shrinking the linear viscoelastic regime, making the sludge system sensitive to shear. Thus, both the sludge dewatering rate and moisture reduction efficiency were improved by lowering the pH. These factors demonstrate that rheological analysis can understand the mechanism of acid conditioning on activated sludge dewatering better.