The use of powdered activated carbons in water purification is complicated by the formation of stable suspensions that can remain in water for hours or even days. This reduces the purification efficiency and causes secondary pollution, requiring the development of accelerated particle sedimentation methods. The paper presents a study of the aggregation process of suspended particles of activated carbon brand SPDC-2 during the purification of water from the Penza Reservoir using aluminum sulfate (working concentrations of 20-80 mg/l) and a flocculant based on polyacrylamide AC-631 (working concentrations of 0.02-0.2 mg/l). Microscopic analysis methods have shown that aluminum sulfate provides more effective coagulation compared to polyacrylamide, and its effect increases with increasing concentration. The use of only polyacrylamide does not lead to a pronounced dependence of the aggregation of carbon sorbent particles on the flocculant dosage. The synergistic effect of the combined use of reagents is observed only at polyacrylamide concentrations of 0.1 mg/l and higher at all studied concentrations of aluminum sulfate. In particular, the combination of 0.2 mg/l polyacrylamide and 80 mg/l aluminum sulfate demonstrates maximum efficiency, increasing the average aggregate size to 0.076 mm, and the diameter of the most numerous fraction to 0.105 mm. At the same time, at low flocculant concentrations (0.02 mg/l), combined use with a coagulant does not provide a statistically significant advantage over the use of aluminum sulfate alone, indicating the absence of synergism under these conditions. The results obtained are important for optimizing the reagent treatment of coal suspensions in water treatment processes.