Supplementation of tea polyphenols in sludge Fenton oxidation improves sludge dewaterability and reduces chemicals consumption

The Fenton oxidation improves sludge dewatering but faces notable technical and economic challenges, including a narrow acidic pH range, slow reduction of Fe(III), and the use of high doses of chemicals. Herein, we used a natural polyhydroxyphenol tea polyphenols (TP), as an iron redox conversion enhancer, to mitigate these issues. Compared with the classical Fenton process at pH 3.0, the process with TP (33.8 mg/g dry solids (DS)) improved sludge dewaterability at pH 7.5 in a Fenton-like system with faster Fe(II)/Fe(III) cycling and two times lower consumption of the Fenton reagent. Sludge capillary suction time and specific resistance to filtration decreased from 70 s to 22 s and from 2.7 x 10(13) m/kg to 5.2 x 10(11) m/kg, respectively, while the required doses of Fe(II) and H2O2 were cut to 25 mg/g DS and 31.2 mg/g DS. Mechanistically, TP could bond readily with Fe (II)/Fe(III) at neutral pH to form stable complexes with complexation constants of 34 +/- 161 M-1 and 52 +/-& nbsp;70 M-1, respectively, and reduce part of the Fe(III) to Fe(II) simultaneously. This maintained sufficient soluble Fe in the sludge and boosted efficient conversion of Fe(II)/Fe(III) to yield more hydroxyl radicals (.OH). Subsequently, & BULL;OH oxidation resulted in the decomposition of biopolymers with a molecular weight of 108 Da (e.g., 58.2% of polysaccharides and 31.6% of proteins in tightly bound extracellular polymeric substances) into small molecules and disintegration of bioflocs into smaller particles with increased porosity, contact angle, and cell lysis; these changes helped reduce bound water content and improved sludge dewaterability. In addition, the TP-mediated Fenton process disinfected fecal coliforms in the sludge and preserved the sludge organic matters. This work proposes a new paradigm for developing cost-effective sludge dewatering technologies that relies on the synergistic effects of plant polyphenols and advanced oxidation processes.

Automated summary

This study used tea polyphenols as an iron redox conversion enhancer to improve the dewatering efficiency of sludge in the Fenton oxidation process. The addition of tea polyphenols in a Fenton-like system enhanced the sludge dewaterability at neutral pH, reduced the consumption of Fenton reagents, and resulted in the decomposition of biopolymers and disintegration of bioflocs. This research suggests a new approach for cost-effective sludge dewatering technologies using the synergistic effects of plant polyphenols and advanced oxidation processes.