Enhanced dewaterability of waste activated sludge with Fe(II)-activated hypochlorite treatment

Abstract

A novel method was explored to improve the waste-activated sludge (WAS) dewaterability using Fe(II) combined with calcium hypochlorite, and the possible mechanisms were investigated simultaneously. Capillary suction time (CST), specific resistance to filtration (SRF) of sludge, and water content (W) of dewatered sludge cake were selected as the factors to evaluate the sludge dewaterability. The maximum reduction of W (30.76%) was achieved under the optimal conditions of Ca(ClO) 0.04 g/g total suspended solids (TSS), FeSO·7HO 0.097 g/g TSS, and pH 7.3, while the reduction of CST and SRF reached 91.24 and 99.47%, respectively. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy of extracellular polymeric substances (EPSs) showed that sludge dewaterability was mainly related to the degradation of tryptophan and tyrosine protein-like substances in sludge EPS. Economic analysis suggested Fe(II) combined with calcium hypochlorite treatment had greater potential on enhancing WAS dewaterability compared with the traditional sludge treatment.

Pyrite activated peroxymonosulfate combined with as a physical–chemical conditioner modified biochar to improve sludge dewaterability: analysis of sludge floc structure and dewatering mechanism

“…After AOP treatment, the zeta potential rose to − 12.4 mV within 5 min. However, over time, the best zeta potential of WAS after the AOP treatment remained at − 10.4 mV, which differs from previous results (Ai et al 2021 ; Wang et al 2021 ; Zhu et al 2018 ). This situation might have resulted from the continuous release of negatively charged organic matter from internal sludge cells and flocs to the outer space of the sludge and the release of biopolymers with the same charge, which repel each other in the AOP.…”

New Insight on the Combined Effects of Hydrothermal Treatment and FeSO4/Ca(ClO)2Oxidation for Sludge Dewaterability Improvement: Moisture Distribution and Noncovalent Interaction Calculation

“…Moreover, as can be observed in Table 1, the free radicals' concentrations were closely related to the pH value. The lower the pH value, the higher the free radical concentration, which was agreed with Zhu et al 39 that…”

“…Moreover, as can be observed in Table , the free radicals’ concentrations were closely related to the pH value. The lower the pH value, the higher the free radical concentration, which was agreed with Zhu et al that the influence of pH on the FeSO 4 ·7H 2 O/Ca­(ClO) 2 oxidation process was mainly through the generation rate of free radicals. At the acid and neutral pH, Ca­(ClO) 2 is expected to produce HOCl, and it may generate more free • OH in the presence of FeSO 4 ·7H 2 O.…”

Waste sludge disintegration and bound water reduction by chemical oxidation: A comparative study

“…When compared to the traditional Fenton process, the hypochlorite salt can catalyze Fe 2 + over a wide pH range and produce OH • [16][17]. However, there are few studies in sludge treatment on the use of Fe 2 + activated hypochlorite treatment which is widely used in wastewater treatment [18]. Similar to H 2 O 2 oxidation, OH • , which is generated by the hypochlorite salt, ensures the trapped water in the bacterial cell and the bound-water in the extracellular polymeric substances (EPS) to be released as well as cell destruction, sludge minimization and disintegration.…”