Evaluation of the Main Parameters Influencing Sludge Treatment Processes in Activated Sludge Municipal Wastewater Treatment Plants Employing the Clay Material Nano Montmorillonite Conditioner

Document Type : Research Paper

Authors

1 Department of Water, Wastewater and Environmental Engineering, Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran, Iran

2 Department of Water, Wastewater and Environmental Engineering, Faculty of Civil, Water and Environmental Engineering, Shahid Beheshti University.Tehran. Iran

Abstract

Objective: The efficient operation of excess biological sludge treatment processes, including thickening, digestion, and dewatering, is crucial to the overall performance of activated sludge wastewater treatment systems. This study aimed to evaluate the key operational parameters affecting these stages in order to optimize the use of nano montmorillonite and its acid–thermally modified form as sludge conditioners. The objective was to assess the effectiveness of these materials in improving sludge dewaterability, enhancing sludge digestibility, and increasing methane production
Method: Laboratory-scale experiments were conducted using real sludge samples, provided from the South Tehran Wastewater Treatment Plant. The primary parameters assessed included time to filtration (TTF), specific resistance to filtration (SRF), capillary suction time (CST), zeta potential, bound water content, and sludge digestibility. Pearson correlation analysis was applied to explore the relationships between the nanomaterials and these parameters. Additionally, a heatmap was generated to illustrate the interdependencies among them.
Results: The greatest reduction in SRF was observed with 300 mg/g dry solids of nano montmorillonite, yielding SRF values of 6.7×10¹² and 52.8×10¹² m/kg for excess and digested sludge, respectively. Using 200 mg/g of the modified form produced SRF values of 6.2×10¹² and 45.3×10¹² m/kg for excess and digested sludge, respectively. At the same optimal dosages, TTF and CST were improved significantly by nano montmorillonite and its acid-thermal modified: 31, 26, 2, and 2.3 seconds for excess sludge and 192, 164, 6, and 5 seconds for digested sludge, respectively. The modified nanomaterial reduced zeta potential and bound water content by 93.8% and 80.4% in excess sludge and by 89.7% and 77.9% in anaerobically digested sludge. The heatmap analysis at dosages of 0, 100, 150, 200, 250, 300, and 350 mg/g revealed strong correlations (97–98%) among TTF, CST, and SRF. Therefore, the related results showed methane production improvement in anaerobic digestion phase.
Conclusions: Both investigated materials, nano montmorillonite and acid-thermally modified nano montmorillonite, despite their different dosage requirements, exhibited good performance in sludge conditioning, thickening, and dewatering. In addition, a strong correlation was observed among the three parameters of TTF, CST, and SRF.

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References

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Journal of Environmental Studies
Volume 52, Issue 1
June 2026
Pages 41-61

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