Work

Seasonal Temperature Effects on EPS Composition and Sludge Settling Performance in Full-Scale Wastewater Treatment Plant: Mechanisms and Mitigation Strategies

Year: 2025

Type: article

Abstract: Seasonal temperature variations significantly impact biological wastewater treatment performance, particularly affecting extracellular polymeric substance (EPS) composition and sludge settling characteristics in activated sludge systems. This study investigated the temperature-induced EPS response mechanisms and their effects on nitrogen removal efficiency in a full-scale modified Bardenpho wastewater treatment plant, combined with laboratory-scale evaluation of EPS-optimizing microbial agents for performance enhancement. Nine-month seasonal monitoring revealed that when the wastewater temperature dropped below 15 °C, the total nitrogen (TN) removal efficiency decreased from 86.5% to 80.6%, with a trend of significantly increasing polysaccharides (PS) in dissolved organic matter (DOM) and loosely-bound EPS (LB-EPS) and markedly decreasing tightly-bound EPS (TB-EPS). During the low-temperature periods, when the sludge volume index (SVI) exceeded 150 mL/g, deteriorated settling performance could primarily be attributed to the reduced TB-EPS content and increased LB-EPS accumulation. Microbial community analysis showed that EPS secretion-promoting genera of Trichococcus, Terrimonas, and Defluviimonas increased during the temperature recovery phase rather than initial temperature decline phase. Laboratory-scale experiments demonstrated that EPS-optimizing microbial agents dominated by Mesorhizobium (54.2%) effectively reduced protein (PN) and PS contents in LB-EPS by 70.2% and 54.5%, respectively, while maintaining stable nutrient removal efficiency. These findings provide mechanistic insights into temperature–EPS interactions and offer practical technology for improving winter operation of biological wastewater treatment systems.

Source: Fermentation

DOI: 10.3390/fermentation11090532