Xu, Yang, Jin, Fei  ORCID: https://orcid.org/0000-0003-0899-7063, Liu, Xiaowen, Cheng, Weixin, Yu, Ran, Wan, Jia-Lei, Xie, Jia-Hao and Du, Yan-Jun
2026.
Insights into EPS-mediated simultaneous dewatering and stabilization of landfilled tannery sludge via combined chemical conditioning and PVD-vacuum preloading.
Chemical Engineering Journal
, 178611.
10.1016/j.cej.2026.178611
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Abstract
Landfilled tannery sludge poses severe challenges for in situ dewatering and safe disposal due to high water content and concentrations of Cr and Zn, and abundant extracellular polymeric substance (EPS). This study conditioned unregulated landfilled tannery sludge with polymeric ferric sulfate (PFS) and calcium carbide residue (CCR), and systematically investigated the EPS-driven dewatering, heavy metal immobilization, and clogging mechanisms during prefabricated vertical drain (PVD)-vacuum preloading through microscopic and PVD-vacuum preloading model tests. Both specific resistance to filtration (SRF) and capillary suction time correlated exponentially with total EPS content (R2 = 0.99). PFS-CCR conditioning extensively disrupted EPS fractions and reduced SRF by two orders of magnitude (4.58 × 1014 to 1.68 × 1012 m/kg). Total EPS content also correlated linearly with Cr and Zn leaching concentrations (R2 = 0.92–0.96). Cr and Zn immobilization followed a three-stage sequence of EPS disruption, release, and re-immobilization, increasing the residual fractions of Cr and Zn from 25.7% and 20.9% to 73.0% and 75.2%, respectively. PVD-vacuum preloading model tests revealed, for the first time, radial migration of EPS and colloidal particles toward the PVD, with their changes significantly correlated with changes in heavy metal leaching concentrations. In unconditioned sludge, the EPS gel network entrapped colloidal particles and heavy metals, co-migrating toward the PVD and inducing clogging at the filter membrane and pore throats, resulting in poor dewatering. PFS-CCR conditioning disrupted the EPS gel network, suppressed migration of EPS and colloidal particles, and reduced water content below 60% at all radial positions, with uniform heavy metal leaching concentrations meeting remediation targets.
| Item Type: | Article |
|---|---|
| Date Type: | Published Online |
| Status: | Published |
| Schools: | Schools > Engineering |
| Additional Information: | RRS applied |
| Publisher: | Elsevier |
| ISSN: | 1385-8947 |
| Date of First Compliant Deposit: | 10 July 2026 |
| Date of Acceptance: | 19 June 2026 |
| Last Modified: | 10 Jul 2026 11:00 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/188041 |
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