Abstract: Dehydration through mechanical pressure filtration is widely used for dehydrating river and lake sludge. The conditioning of the sludge significantly impacts the efficiency of mechanical filtration dehydration. Two common conditioning measures include utilizing flocculant with polyacrylamide (PAM) and employing a compound conditioning approach that combines flocculant with an inorganic conditioner. In recent years, compound conditioning methods have seen rapid development. Studying the impact of single and compound conditioning of flocculants on the efficiency and mechanism of mechanical filtration dehydration is crucial. Focusing on the sludge sourced from Guantian Lake, this study compares the conditioning performance of PAM and LAC and their dehydration performance, and analyzes the dehydration technical parameters in PAM and PAM+LAC conditioning cases. The effect of composite conditioning on the structure of dehydrated sludge cake is also revealed via mercury intrusion test and SEM scanning. Findings indicate that the conditioning agent primarily enhances the filtration and dehydration stages, as evidenced by water loss meter tests aligning well with the plate and frame mechanical filtration press results. The use of LAC as a supplement to PAM can improve the unloading performance of the sludge cake by enhancing conditioning effects. Microscopic analysis revealed that LAC enlarged the pore size of the sludge cake and increased the proportion of open pores.

Key words: sludge, compound conditioning, dehydration mechanism, mercury intrusion test, pore characteristics