Sludge biodrying coupled with photocatalysis improves the degradation of extracellular polymeric substances.

The efficiency of sludge dewatering is limited by extracellular polymeric substances (EPS) during biodrying. This study investigated the effect of photocatalysis-mediated EPS degradation on sludge dewatering performance during the sludge biodrying process. The photocatalysis of municipal sludge was first carried out to choose a cost-efficient catalyst. Then sludge biodrying tests were performed using TiO 2 -coated amendment (T CA) and uncoated amendment (T UCA) as the control. Municipal sludge photocatalysis results showed that using TiO 2 could efficiently degrade carbohydrates and proteins in the EPS within 60 min. After 20-day biodrying, photocatalysis significantly promoted a reduction in the moisture content and EPS by 17.64% and 6.88%, respectively. The surface-enhanced Raman scattering (SERS) intensities of the C–C–O symmetric stretching vibration peak of D-lactose and the C–S stretching vibration peak of cysteine were significantly decreased by approximately 33.19% and 44.76%, respectively, indicating that photocatalysis indeed promoted the reduction of polysaccharides and cysteine in the EPS, especially after the thermophilic phase. The hydrophilic amino acid content decreased by 23.02%, verifying that photocatalysis could improve EPS hydrophobicity. Consequently, municipal sludge biodrying coupled with photocatalysis promotes sludge EPS degradation and enhances sludge dewaterability, improving the efficiency of sludge biodrying. [Display omitted] • TiO 2 coated amendment was used during sludge biodrying with photocatalysis. • Polysaccharide in extracellular polymeric substance degraded after thermophilic phase. • Cysteine C–S stretching vibration intensity reduced 29.44% after thermophilic phase. • Significant degradation of hydrophilic lysine and cysteine promoted sludge dewatering. • Using TiO 2 coated amendment biodrying showed high humification and low biotoxicity. [ABSTRACT FROM AUTHOR]