Enhanced Sludge Dewaterability and Pathogen Inactivation by Synergistic Effects of Zero-Valent Iron and Ozonation

Abstract

In this study, the efficiency of the combined zerovalent iron (ZVI) and ozone (O 3 ) treatment at a pH of 2 (acid-ZVI-O 3 ) for simultaneous improvement of sludge dewaterability and pathogen inactivation was investigated. The results showed that the ozone treatment alone deteriorated sludge dewaterability, while the introduction of acid-ZVI into the ozone treatment could significantly enhance the sludge dewaterability. At the optimal conditions with 30 mg O 3 g −1 of total solid (TS) and 63 mg ZVI g −1 of TS at a pH of 2, the capillary suction time of conditioned sludge was 1.63 s L g −1 TS, which was much smaller than those of raw sludge (10.45 s L g −1 TS), the single ozonation treated sludge (16.07 s L g −1 TS), and the acid-ZVItreated sludge (6.98 s L g −1 TS). The acid-ZVI-O 3 treatment promoted the generation of hydroxyl radicals and showed synergistic effects in removing key hydrophilic substances which would deteriorate sludge dewaterability, i.e., humic acid-like compounds and soluble microbial byproduct-like substances in the tightly bound extracellular polymeric substances (TB-EPSs). Ferric iron was generated therein and worked as a coagulant to agglomerate sludge particles. The enhanced sludge dewaterability was further confirmed by a laboratory-scale diaphragm filter press. Moreover, the acid-ZVI-O 3 treatment showed an effective inactivation of pathogens, which was below the limit specified for class A biosolids, according to the US EPA standard. As such, enhanced sludge dewaterability and pathogen inactivation can be simultaneously achieved with the acid-ZVI-O 3 treatment.

Enhanced dewaterability of waste-activated sludge with zero-valent iron-activated persulfate oxidation under mild hydrothermal conditions

“…The detailed results are shown in Figure 3. Regions I, II, III, IV, and V in the 3D-EEM were aromatic protein-like, tryptophanlike proteins, fulvic acid-like materials, soluble microbial product, and humic acid-like, respectively (Yu et al 2018a(Yu et al , 2018b. The 3D-EEM results indicated that regions I, II and IV were predominant in the EPS fraction of RS (Figure 3(a)).…”

“…Recently, hydrothermal treatment (HT) has gained attention due to its advantages of high efficiency and high value-added products (Yu et al 2018a(Yu et al , 2018b. HT could promote the decomposition of sludge flocs, especially EPS, and reduce viscosity (Wang et al 2017).…”

Inactivation and risk control of pathogenic microorganisms in municipal sludge treatment: A review

“…The persulfate at 0.5 mM activated by solar energy may contribute to a 6.0 log unit reduction in bacteria in sewage after 2 h of reaction (Ferreira et al, 2020). The combined use of ozone and zerovalent iron (ZVI) at doses of 30 and 63 mg/g TS may contribute to the reduction in the total coliforms and E. coli in sludge by 98.6% and 97.7%, respectively, and OH was reported to play an important role (Yu et al, 2019c). Wang et al compared five pretreatment approaches for pathogen inactivation in sewage sludge, and electric-Fenton reactions exhibited the best performance and contributed to the removal of coliform and E. coli by 4.84 log units and 3.86 log units after 60 min (Wang et al, 2021).…”

Solid–Liquid Distribution of Ciprofloxacin during Sludge Dewatering after Fe(II)-Activated Peroxymonosulfate Treatment: Focusing on the Role of Dissolved Organic Components

“…Among these, advanced oxidation processes, particularly sulfate radical (SO 4 ·– )-based treatments, have been widely used to enhance sludge dewaterability . The dewatered sewage sludge cake can be used as a fertilizer in agriculture, as the sludge contains nutrients like carbon (55%), nitrogen (15%), and phosphorus (3%) . At the same time, however, sewage sludge is also a sink for undesirable wastewater components from human medication, particularly antibiotics .…”