The intensification of wastewater sludge treatment processes remains a critical challenge for modern wastewater treatment plants, due to high moisture content, large sludge volumes, and the operational burden of sludge stabilization and dewatering. This study investigates the enhancement of gravitational thickening and subsequent aerobic stabilization of activated sludge through preliminary coagulation treatment. Laboratory experiments were conducted using 500 mL sludge samples subjected to gravitational settling under controlled conditions. Two coagulant-treated samples were compared with an untreated control. The dynamics of the sludge-water interface displacement were monitored over time, and settling velocity was calculated as a function of the change in sludge layer height per time interval. The settling process demonstrated a pronounced initial compaction phase within the first 30 minutes. During this period, sludge volume decreased from 500 mL to 460 mL in the control sample (8%), to 455 mL with coagulant 1 (9%), and to 445 mL with coagulant 2 (11%). After 60 minutes, the sludge volumes reached 410 mL, 395 mL, and 390 mL, respectively, corresponding to a total compaction of 18–22%. These results confirm the acceleration of phase separation and the formation of a denser sludge structure due to coagulation. Following thickening, the sludge underwent aerobic stabilization for 6 days. Changes in physicochemical parameters indicated structural consolidation and partial mineralization of the organic fraction. The integration of coagulation and gravitational thickening reduced the expected volume of return liquor to approximately 3–10% of the treated sludge volume. Furthermore, preliminary thickening improves the structural characteristics of sludge prior to mechanical dewatering, potentially increasing dewatering efficiency by 10–20%. The obtained results demonstrate that coagulation-assisted gravitational thickening is an effective method for intensifying sludge treatment processes and provide a scientific basis for scaling up the proposed integrated technology within existing wastewater treatment schemes.
Author Biographies
A. B. Mosiichuk, Institute of Water Problems and Land Reclamation NAAS, Kyiv
postgraduate student
M. V. Yatsiuk, Institute of Water Problems and Land Reclamation NAAS, Kyiv
