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<p>To further elucidate the mechanism by which citric acid chelates divalent iron ions to activate the persulfate system (CA/Fe(II)/PDS) for improved sludge dewatering, this study investigates the impact of reagent dosage on the CA/Fe(II)/PDS system. The dosage optimization under varying conditions using response surface methodology is also detailed. The study further analyzes the changes in the physicochemical properties of sludge and the contribution of the involved oxidative radicals. The results indicate that the CA/Fe(II)/PDS system significantly enhances the moisture content of sludge (Wc = 68.78%) compared to the PDS and Fe(II)/PDS systems. Under optimal dosage conditions (PDS = 2.01 mmol/VSS, Fe(II) = 2.15 mmol/VSS, CA = 0.31 mmol/VSS), the capillary suction time (CST) of the sludge is minimized to 7.9s. Notably, the absolute value of the Zeta potential and the soluble chemical oxygen demand (SCOD) reach substantial values of 0.01 mV and 518.60 mg/L, respectively, under these conditions. Further investigations reveal that the addition of citric acid facilitates the conversion of Fe(III) complexes to Fe(II), thereby enhancing the contribution of oxidative radicals (SO4•−) to sludge dewatering improvement (63.54%). Transforming total bound extracellular polymeric substances (TB-EPS) to other forms of EPS (a reduction of 44.3%) is a key factor in sludge dewatering. These findings provide significant insights into exploring green and efficient sludge dewatering methods.</p> Graphical Abstract <p></p>

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Feasibility and Optimization Conditions for Enhancing Dewatering Efficiency of Residual Sludge in a Citrate-Fe(II) Activated Persulfate System

  • 期刊论文

  • 发表日期：

    2025年6月7日

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  • Xiaoyan Liu,
  • Tian Wan,
  • Wen Cheng,
  • Jingxin Sun,
  • Jiehui Ren,
  • Min Wang

摘要

To further elucidate the mechanism by which citric acid chelates divalent iron ions to activate the persulfate system (CA/Fe(II)/PDS) for improved sludge dewatering, this study investigates the impact of reagent dosage on the CA/Fe(II)/PDS system. The dosage optimization under varying conditions using response surface methodology is also detailed. The study further analyzes the changes in the physicochemical properties of sludge and the contribution of the involved oxidative radicals. The results indicate that the CA/Fe(II)/PDS system significantly enhances the moisture content of sludge (Wc = 68.78%) compared to the PDS and Fe(II)/PDS systems. Under optimal dosage conditions (PDS = 2.01 mmol/VSS, Fe(II) = 2.15 mmol/VSS, CA = 0.31 mmol/VSS), the capillary suction time (CST) of the sludge is minimized to 7.9s. Notably, the absolute value of the Zeta potential and the soluble chemical oxygen demand (SCOD) reach substantial values of 0.01 mV and 518.60 mg/L, respectively, under these conditions. Further investigations reveal that the addition of citric acid facilitates the conversion of Fe(III) complexes to Fe(II), thereby enhancing the contribution of oxidative radicals (SO4•−) to sludge dewatering improvement (63.54%). Transforming total bound extracellular polymeric substances (TB-EPS) to other forms of EPS (a reduction of 44.3%) is a key factor in sludge dewatering. These findings provide significant insights into exploring green and efficient sludge dewatering methods.

Graphical Abstract