Enhancement of waste-activated sludge dewaterability using combined fenton pre-oxidation and flocculation process

A combination of Fenton pre-oxidation and flocculation process was utilized to enhance the dewaterability of waste-activated sludge. The dry solid content of dewatered sludge (DS) cake, supernatant turbidity, sludge specific resistance to filtration (SRF), supernatant of soluble chemical oxygen demand (SCOD), polysaccharides, and proteins concentration were examined to evaluate the sludge dewatering performance and describe the mechanism involved in sludge treatment. The optimal conditions were as follows: 40 mg·g⁻¹ DS H₂O₂; 50 mg·g⁻¹ DS Fe²⁺; pH 3; Fenton reaction time, 90 min; and 60 mg·L⁻¹ cationic polyacrylamide (CPAM). Under these conditions, the optimal SRF and DS achieved were 1.21 × 10⁹ m·kg⁻¹ and 34.20%, respectively. The extracellular polymeric substance structure was destroyed by Fenton oxidation. Consequently, polysaccharide and protein were released into the supernatant, and the SCOD was increased. Morphological property analysis revealed an evident compact sludge floc after the combined Fenton pre-oxidation and flocculation process. The sludge particle treated with the combined processes became larger than that treated with Fenton oxidation alone. The sludge flocs were formed with the addition of CPAM during flocculation due to its excellent charge neutralization and bridging ability. The present results showed that the combination of Fenton pre-oxidation and flocculation is effective in conditioning waste-activated sludge and consequently enhancing sludge dewaterability.