Effects and conditioning mechanisms of sludge dewaterability by activating persulfate with a combination of ultraviolet light and ferrous iron

LAN Mei; YANG Pei-sen; ZHANG Hui-long; KONG Jia-lu

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China Environmental Science ›› 2026, Vol. 46 ›› Issue (1) : 238-247.

Effects and conditioning mechanisms of sludge dewaterability by activating persulfate with a combination of ultraviolet light and ferrous iron

LAN Mei, YANG Pei-sen, ZHANG Hui-long, KONG Jia-lu

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Abstract

A combined conditioning system using NaClO as the oxidizing agent was employed to condition sludge. The variations in sludge dewatering performance before and after conditioning were investigated to validate the enhancing effect of ultraviolet irradiation on the advanced oxidation process. Meanwhile, the reasons for the deterioration in dewatering performance were discussed when NaClO was added alone. The effects of dosage ratios (NaClO/FeSO₄), Fe²⁺ dosage, and pH value on sludge dewatering performance were investigated using the capillary suction time (CST) and specific resistance to filtration (SRF) as key evaluation indicators. The results demonstrated that the ultraviolet irradiation activated a higher concentration of strong oxidative free radicals based on the activation of Fe²⁺ towards NaClO, thereby promoting the decomposition of EPS. With the addition of UV irradiation, the CST reduction rate increased from 61.5% to 65.4%, while the SRF reduction rate increased from 71.4% to 79.8%. During the experiment, the TB-EPS of the sludge were converted into the LB-EPS of the sludge. As a result of this conversion, the decomposition and oxidation of protein played a crucial role in enhancing sludge dewaterability. Analysis revealed that the deterioration in dewatering when NaClO was added alone was attributable to the insufficient oxidation capacity within the system and the excessive formation of bubbles during the conditioning process.

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sludge dewatering / UV/Fe²⁺/NaClO / advanced oxidation process / extracellular polymeric substances (EPS)

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LAN Mei, YANG Pei-sen, ZHANG Hui-long, KONG Jia-lu. Effects and conditioning mechanisms of sludge dewaterability by activating persulfate with a combination of ultraviolet light and ferrous iron[J]. China Environmental Science. 2026, 46(1): 238-247

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