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.
Highlights
Sewage sludge, a by-product of wastewater treatment, contains a large amount of water that can be generally divided into free and bound water [1,2,3]
The WC and capillary suction time (CST) decreased to 63.36% and 31.8 s (Fig 1a), respectively, when the H2O2 dosage was increased to 40 mg/g
The finding was in agreement with that reported by Zhou et al [5], who observed that adding more H2O2 cannot further improve the sludge dewaterability
Summary
A by-product of wastewater treatment, contains a large amount of water that can be generally divided into free and bound water [1,2,3]. Sludge conditioning and dewatering are essential to improve sludge dewaterability. Organic polymers can facilitate the flocculation of sludge particles by charge neutralization or adsorption bridging mechanism but do not affect the water molecule-organic matter bonding in the sludge. Liu et al [7] demonstrated that 84% specific resistance to filtration (SRF) reduction efficiency was achieved when 20 mg/g Fe2+ and 125 mg/g H2O2 were added to the sludge. Their studies [8,9,10] reported that the addition of Fenton’s reagent increases the extracellular polymeric substance (EPS) concentration in the sludge supernatant, leading to significant effects on sludge dewatering performance
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