Electrokinetic dewatering, consolidation and strengthening of fine tailings: a large tank test using ePVD electrodes to inform a field trial

Authors: Lamont-Black, J; Chamberlain, M; Hartog, T Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2615_61

Cite As:
Lamont-Black, J, Chamberlain, M & Hartog, T 2026, 'Electrokinetic dewatering, consolidation and strengthening of fine tailings: a large tank test using ePVD electrodes to inform a field trial', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-18, https://doi.org/10.36487/ACG_repo/2615_61



Abstract:
Tailings storage facilities (TSFs) for fine-grained mine waste often take decades to self-consolidate and gain enough strength after closure to allow safe rehabilitation and spread of growth media. Often, large volumes of imported granular fill to construct access roads are required. While electrokinetic dewatering offers a means to accelerate dewatering and strength gain, this was historically cost prohibitive due to use of metal electrodes. Development of low-cost polymer electrodes has made electrokinetic dewatering a potential economic option. Central Alliance was engaged by a tier 1 mining company to develop a techno-economic model for electrokinetic treatment, including the design and implementation of a full-scale trial. The results of the second stage of development are presented here. A large outdoor tank test was undertaken on iron ore tailings to validate bench-scale test findings under realistic climatic conditions and at a 1:1 scale in plan, with the results and practical experience feeding into the design of a full-scale in situ electrokinetic treatment trial. The set-up comprised a 3 m diameter tank filled to 0.9 m depth with fine iron ore tailings. Six polymer electrokinetic geosynthetic (EKG) anodes were arranged in a hexagon around a central polymer EKG cathode drainage conduit. During an initial 7-day settling period, the water content (wet basis) reduced from 44.0% to 41.2%. On application of direct current at 50 V, drainage at the cathode peaked, then dropped to zero after 37 days of near-continuous treatment, when a water content of 25.5% was determined. Electrokinetic treatment continued until day 60, with no further drainage at the cathode. Water content continued to fall, reaching 17.6% at completion. Over the treatment period, the average hand vane shear strength increased from 2.7 kPa at the start to 37 kPa at day 48, after which the material became too stiff to test. Average tailings thickness reduced from 889 mm to 671 mm over the test period. Total energy consumption was 39.1 kWh, equivalent to 6.2 kWh/m³. A key observation was the development of large desiccation cracks that disrupted electric field pathways and reduced the electrode–soil contact, decreasing electroosmotic efficiency. However, the surface area available for evaporation was increased significantly, likely contributing to increased moisture loss. The test demonstrated substantial moisture loss and strength gains, providing essential data and practical experience for the next steps of design and implementation of a full-scale field trial over a proposed treatment area of 30 × 30 m and depth of 5–10 m. The polymer EKG electrodes were shown to perform as required, with no signs of degradation, offering a low-cost alternative to metal electrodes, opening the possibility of economic widespread implementation of electrokinetic treatment and accelerating TSF closure programs.

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