Bioconditioning-driven enhancement of sewage sludge dewaterability via EPS modification by Acidithiobacillus ferrooxidans

This study proposes a bioconditioning method using Acidithiobacillus ferrooxidans (A.f) to improve sewage sludge dewaterability. Application of A.f whole culture reduced the specific resistance to filtration (SRF) by 87.9%. This significantly outperformed chemical conditioning, which achieved a 30.8% reduction at pH 3.19. Excess sludge has high water content and is difficult to dewater. Chemical methods often leave residues and have limited effect. A.f was tested in three forms: whole culture, cell-free filtrate, and culture with Fe²⁺ addition. FTIR and Raman spectroscopy showed that A.f degraded extracellular polymeric substances (EPS) into simpler compounds, such as amino acids and polysaccharides. These changes improved floc structure and enhanced water release. Monitoring of pH, oxidation–reduction potential (ORP), Fe2+, and sulphate confirmed microbial oxidation as the key mechanism. The process relies on A.f metabolic activity rather than external reagents. This lowers chemical usage and environmental impact. The findings demonstrate that A.f-based conditioning is efficient, sustainable, and more effective than traditional methods. This work also reveals how microbial–EPS interactions contribute to improved sludge treatment.