Influence of extracellular polymeric substances on rheological properties of activated sludge

Influence of extracellular polymeric substances (EPS) on rheological properties of activated sludge (AS) was conducted by comparing properties of AS before and after EPS extraction at a TSS of 54 g/L. Slime, loosely and tightly bound EPS (LB- and TB-EPS) were stratified by centrifugation and ultrasound method. The results showed that sludge after LB-EPS extraction produced a higher hysteresis loop area (Hla), limiting viscosity (η∞), yield stress (τy), energy of cohesion of network sludge (Ec), and storage modulus (G′0), than three other sludge samples, indicating that sludge with TB-EPS exhibited stronger network structure. Strain amplitude sweep (SAS) and frequency sweep (FS) tests revealed that AS before and after EPS extraction produced a gel-like structure in the linear viscoelastic (LVE) domain. TB-EPS appeared to have a positive effect on the gel-like structure of AS.