Heavy Metal Passivation and Microbial Community Succession during Anoxic-Aerobic Digestion of Municipal Sludge

Ruihua Mu; Kaige Zhang; Wenzhuo Chen; Xiaoqian Shi; Fengqiu An; Ye Liu

doi:10.62177/jaet.v3i2.1383

Authors

Ruihua Mu Xi'an Polytechnic University
Kaige Zhang Xi’an Polytechnic University
Wenzhuo Chen Xi’an Polytechnic University
Xiaoqian Shi Xi’an Polytechnic University
Fengqiu An Xi’an Polytechnic University
Ye Liu Xi’an Polytechnic University

DOI:

https://doi.org/10.62177/jaet.v3i2.1383

Keywords:

Municipal Sludge, Anoxic-Aerobic Digestion, Heavy Metal Passivation, Nitrogen and Phosphorus, Microflora

Abstract

Although anoxic-aerobic digestion has garnered widespread attention as an emerging sludge treatment technology, the mechanisms governing microbial community succession and heavy metal passivation remain incompletely elucidated. In this study, a sequencing batch reactor (SBR) was operated under alternating anoxic-aerobic conditions (dissolved oxygen = 4 mg/L; sludge retention time = 30 days) to systematically investigate these underlying mechanisms. The alternating environment effectively promoted the migration of heavy metals from the liquid to the solid phase, thereby achieving successful passivation. The liquid-phase zinc (Zn) concentration peaked at 5.76 mg/L before subsequently decreasing, whereas the solid-phase Zn concentration remained stable, reaching a maximum of 57.43 mg/g. Highly toxic cadmium (Cd) was not detected at any point during the operation. Furthermore, the system demonstrated significant nutrient recovery potential, as liquid-phase phosphate accumulated to 2902.81 µg/L. High-throughput sequencing revealed that the alternating redox environment fundamentally reshaped the microbial community structure. Although overall microbial diversity decreased, the functional phyla Chloroflexi (34.08%) and Proteobacteria (19.50%) maintained their dominance. Additionally, the abundance of pathogenic genera, including Acinetobacter, was markedly reduced. These specific microbial successions were intrinsically driven by the anoxic-aerobic digestion process and exhibited a strong correlation with heavy metal passivation. Ultimately, these findings offer a sustainable and effective approach for the safe disposal and resource utilization of municipal sludge.

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