Mechanism and Parameter Optimization of Fenton’s Reagent Integrated with Surfactant Pretreatment to Improve Sludge Dewaterability

Abstract

Sludge dewatering can effectively reduce the volume and mass of sludge for subsequent treatment and disposal. The work validated the potential of Fenton’s reagent combined with dodecyl dimethyl benzyl ammonium chloride (DDBAC) in improving sludge dewaterability and proposed the mechanism of joint conditioning. The composite conditioner dosage was optimized using response surface methodology. Results indicated the good conditioning capability of the composite conditioners. The optimum dosages for H2O2, Fe2+, and DDBAC were 44.6, 39.6, and 71.0 mg/g, respectively, at which a sludge cake water content of 59.67% could be achieved. Moreover, a second-order polynomial equation was developed to describe the behavior of joint conditioning. Analysis of the reaction mechanism showed that Fenton oxidation effectively decomposed extracellular polymeric substance (EPS), including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), into dissolved organics, such as proteins and polysaccharides. The process facilitated the conversion of the bound water into free water. Furthermore, DDBAC further released the bound water through solubilization of TB-EPS and LB-EPS after the Fenton reaction. The bound water content of the sludge conditioned with Fenton’s reagent decreased from 3.15 to 1.36 g/g and further decreased to 1.08 g/g with the addition of DDBAC. High-performance liquid chromatography analysis verified that the composite conditioning could oxidize and hydrolyze EPS into low-molecular-mass organics (e.g., formic and acetic acid), thereby facilitating the release of bound water.

Effective sludge dewatering technique using the combination of Fenton's reagent and CPAM

“…However, excessive H 2 O 2 does not lead to further increase in dewatering efficiency. Excessive H 2 O 2 had a negative effect on the generation of •OH, and the concentration of •OH was low …”

“…Excessive H 2 O 2 had a negative effect on the generation of •OH, and the concentration of •OH was low. [36] Initially, few hydroxyl radicals (•OH) were generated because of the low Fe 2þ concentration, the reaction was inhibited, and the effect of oxidation was poor. [37] With the increase of Fe 2þ , the efficiency of the Fenton reaction improved, and the concentration of •OH increased rapidly.…”

Mechanistic Understanding of Beneficial Aspects of Iron Salts and Waterworks Sludge Uses in Urban Wastewater System

“…There are a number of parameters characterizing the physicochemical properties of sludge, which are reported to have a direct or indirect influence on sludge dewaterability. This includes concentrations and properties of different extracellular polymeric substance (EPS) fractions (soluble/loosely-bound/tightly-bound) and bound water content (BWC) (Niu et al, 2013;Xing et al, 2017). Li and Yang (2007) reported deterioration in digestate dewaterability with increment in soluble-EPS wherein Novak et al (2003) concluded otherwise.…”