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Effects of phase separation on dewaterability promotion and heavy metal removal of sewage sludge during bioleaching

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Abstract

Bioleaching is of increasing interest because of its high efficiency in improving sludge dewaterability and removing heavy metals from sewage sludge. However, in traditional single-phase bioleaching, a high-efficiency level cannot be maintained continuously, wherein the microbial synergistic effect is disrupted at a low pH environment. Therefore, in this study, a series of multi-compartment–baffled flow trials were performed to assess the effects of phase separation on sludge bioleaching by comparing a two-phase trial with two single-phase trials. Energy substrate and part of the bioleached sludge were introduced separately into two compartments to form two phases, namely selection phase and bioleaching phase. The results show that phase separation apparently shortened the start-up duration of sludge bioleaching from 7 days in a single-phase bioleaching to 4 days in two-phase bioleaching. The dewaterability of bioleached sludge was also enhanced by phase separation with relative decreases of 25.0–33.3% for specific resistance to filtration and 14.2% for capillary suction time, which was attributed to lower pH values, zeta potential closer to zero, and less dissolved organic matter in bioleached sludge after two-phase bioleaching. Phase separation generally increased the removal ratios of heavy metals during sludge bioleaching by −0.79 to 2.60%, 11.06 to 15.04%, 4.45 to 11.03%, 17.98 to 23.46%, 7.20 to 9.28%, −9.22 to −2.46%, and −6.72 to −10.68% for As, Cd, Cr, Cu, Ni, Pb, and Zn, respectively. Phase separation also enriched the Acidithiobacillus spp. and reduced the inactivation of acid-tolerant fungi, which can be conducive to better synergistic effect, and therefore maintain long-term stable state in the bioleaching phase of the two-phase bioleaching process.

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All data generated or analyzed during this study are included in this published article.

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Acknowledgements

The authors are thankful to Guilin Drainage Management Office for providing sewage sludge samples.

Funding

This study was supported by the National Natural Science Foundation of China (51868011), the Department of Science and Technology of Guangxi (2018GXNSFGA281001), and the Special Fund for Guangxi Distinguished Experts.

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Contributions

JZ and HL conceived the project and designed the experiments. JZ and YL majorly contributed in writing the manuscript. RW performed the experiment. YD revised this manuscript. All authors participated in the entire experimental process. All authors have read and approved the final manuscript.

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Correspondence to Jun Zhang.

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The authors declare no competing interests.

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Responsible Editor: Ta Yeong Wu

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Lu, Y., Wu, R., Zhang, J. et al. Effects of phase separation on dewaterability promotion and heavy metal removal of sewage sludge during bioleaching. Environ Sci Pollut Res 29, 13971–13982 (2022). https://doi.org/10.1007/s11356-021-16630-3

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  • DOI: https://doi.org/10.1007/s11356-021-16630-3

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