Dewatering efficiency of sewage sludge during Fe-activated persulfate oxidation: Effect of hydrophobic/hydrophilic properties of sludge EPS.

To clarify the effect of the hydrophobic/hydrophilic polarity of extracellular polymeric substances (EPS) on sludge filterability improvement during SO/Fe oxidation, waste activated sludge (WAS), glucose-fed hydrophilic sludge (HPI-WAS), and sodium acetate-fed hydrophobic sludge (HPO-WAS) samples were cultivated, and their dewatering behaviors were individually explored. Experimental results showed that SO oxidation effectively disintegrated the polymeric EPS and led to a more significant reduction in the water content for HPO-WAS than for HPI-WAS (12.87-15.23% vs 9.31-12.12%), especially regarding the bound water (W) content. After oxidation, as high as 38.88-42.61% of the W within HPO-WAS samples were declined, much higher than the HPI-WAS samples (19.27-29.20%). Specifically, carbohydrates within sludge EPS negatively influenced the dewatering process of SO/Fe oxidation. By contrast, abundant existence of humic acids and polymeric proteinaceous components (especially those hydrophilic proteins and transitional humic acids) within the sludge EPS exhibited a converse trend. FT-IR and EEM spectral, as well as particle sizes variation for the sludge samples before and after SO/Fe oxidation was also evaluated. This study provides new insight into the enhancement of SO/Fe oxidation for sludge dewatering based on polarity analysis of EPS.