Dewatering is an important process in red-mud tailings management due to the high amount of water remaining after the extraction of aluminium. Excess water will not only reduce the storage capacity of the facility but also increases the liquefaction potential and seepage of the toxic chemicals into the groundwater or vegetation nearby. ‘Farming’ or ploughing/rolling of the surface with special amphibious tractors, known as Amphirols or ‘scrollers’ is usually carried out on settled bauxite residue, to increase the surface area and break the sealed surface, hence accelerating the dewatering process due to evaporation. However, it is unclear how much farming can enhance dewatering, and how the farming should be scheduled to maximise the dewatering outcomes. Laboratory experiments on the dewatering of bauxite residue were conducted to quantify the enhancement of dewatering due to farming. Two tanks were initially filled with settled bauxite residue at the same solids content. The ambient condition was controlled, and the drying of the residues was enhanced by an electrical fan. The residue in one of the tanks was subjected to farming using a downscaled farming scroller while the other tank was not farmed. Moisture sensors, load cells, and cameras were used to quantify the water loss during dewatering. Differences in the dewatering process in the two tanks were analysed, including:
• evaporation rates
• cumulative evaporation
• degree of saturation
• dry density
• crack formation.
This study finds some significant improvement in some of the parameters such as evaporation rate, cumulative evaporation, degree of saturation, dry density, and shrinkage which establishes that the farming method is worthy of further investigation.

Understanding the behaviour of tailings deposited in layers is critical for estimating their long-term settlement and strength in tailings storage facilities. Well-consolidated tailings are stable and can help enhance the deposition efficiency and storage capacity of a tailings storage facility. Unfortunately, that does not take place on many storage facilities that struggle to meet their dry density targets as tailings are being deposited. Different measures have been developed to enhance the strength of tailings, such as adding chemical additives, dry stacking, and farming. As a physical additive, plastic fibres have been widely used to strengthen concrete and soil-cement mixes with very good and reliable results, while their effectiveness is yet to be tested. This is mostly due to the changing sources of tailings and ore extraction process which provide different sets of properties. This study aims to quantify the effect of fibre additives on the settling, consolidation and strength of tailings in order to have a more reliable understanding of how fibres can enhance tailings properties as they are poured and desiccate on storage facilities. Red mud tailings samples with varying percentages of fibre contents mixed with three different plastic fibre types were subjected to settling test in standard settling columns, consolidation, and direct shear tests on samples at different solid contents. Comparisons were made among the tests on tailings with fibre contents and a control test where no additive was added. This paper reports the results obtained from these tests.

The water quality and ecology in the Savage River located on the north-west coast of Tasmania has previously suffered due to historical mining operations from past operators as a result of legacy mine waste rock and tailings storage facilities contributing significant acid and metalliferous drainage to the receiving environment. A series of projects jointly run by the current owners Grange Resources and the government have resulted in synergies and net positive benefits using the current mine operations to manage and remediate legacy mining issues. One such positive example of this synergy is the South Deposit Tailings Storage Facility (SDTSF). The 140 m high facility will provide storage for approximately 37 Mm3 of tailings, equating to approximately 20 years’ tailings storage. The SDTSF embankment is constructed entirely of waste rock won from mining operations and provides Grange with an economical storage solution for waste management (both tailings and waste rock) minimising the sites environmental footprint. The embankment features a permeable filter face which is sufficiently fine to retain tailings and allows passing of normal catchment flows, while larger flood events are stored within the facility and slowly released. Outflows from the filter face are passed to a ‘flow-through’ drain constructed from alkaline, waste rock. The outflows discharged through the ‘flow-through’ will provide a long-term source of alkalinity to Main Creek, subsequently feeding into the Savage River. The facility is showing the first signs of environmental benefits to the downstream ecology that has long been degraded due to the effects of legacy acid and metalliferous drainage (AMD), caused by historical mining operations. Based on initial monitoring following commissioning of the facility in 2017, the filter performance compared with design, along with water quality from the ‘flow-through’ drain.

The quantity of coal tailings (CT) currently discharged annually in Qld and NSW is estimated to be between 14 and 16 million dry tonnes, which is normally disposed in tailings storage facilities (TSF). Due to the continuous mining activities over the last 50 years, the existing tailings storage in Australia has reached an order of 500 million tonnes (Mt), which is emerging as a long-term serious threat to the surrounding environment (Katwal et al, 2022). Despite efforts have been made so far regarding the potential application of mine tailings as construction materials, very little progress has been achieved in the large-scale commercial application of tailings-based products. The reason can be attributed to the limitations of available technology in making cost-effective commercial products.
In this research, the manufacture of road-based aggregates from coal tailings has been investigated as a practical solution, which could not only reduce the volume of tailings that needs to be disposed of but also create a potential new revenue stream for coal producers toward effective dry disposal. It also fits well in the current plans for eliminating TSFs and returning process water for reuse. Dry solids disposal is potentially easier to justify but the quantities involved require other solutions for using the material where this can be shown to be commercially viable. In this regard, the bespoke pelletisation technology developed via a joint research program was used to make aggregates from high concentration solid cake by adding a small amount of cementitious or supplementary cementitious binders/chemicals. By optimising the pelletisation parameters such as the moisture content, rotation speed and tilting angle of the disc, coarse aggregates were successfully produced from coal tailings for the specific use as road-subbase materials. The surface treatment was also conducted to reduce water absorption and improve the durability of aggregates. The proposed solution could provide an economical solution for coal mining companies to address problems associated with coal tailings.

JRI estimated that all Chilean mines have generated more than 50 000 million tons (Mt) of waste (tailings, slags, rocks, among others) which have been stored on the mainland, and the actual mining production of waste is around 5 Mt per day.

Most of the Chilean ore deposits have an expected life of over 100 years, some of them over 200 years, and it estimates that the mining industry will produce more than 150 000 Mt of waste by the end of this century.

More than one-third of the future residues will be stored in the Central Zone of Chile. However, the environmental regulation and communities’ sensibility (majorities against the mining industry) will not allow new residues deposits. Consequently, new technologies should be applied to solve this issue: HD thickening, filtering, over-storage in existing ponds, or backfill.

Existing residues have potential economic value using a polymetallic view (not only copper). A big portion of the existing residues deposited and future residues should be possible to retreat profitably by Secondary mining.

Abandoned pits and underground mines could store a big portion of retreated residues if the government regulations change to permit that easily.

Recently, experimental metallurgical studies permit achievement recoveries of over 70 per cent in all the valuable elements inside residues if they have good commercial grades. It is remarkable the values obtained with rare earths.

This paper shows the statistics of Chilean mining residues, the forecast for the next decades, and alternatives to retreat and restore.
In general, Chile needs strong mining investment to process mining residues profitably.

Over the past years, dam’s breach disasters, fortunately rare, have been investigated revealing that, in many cases, the lack of efficient drainage was one of the main causes of these failures. The accumulation of water into the tailings dam or at the base of them is critical situation engineers and operators want to stay away from to ensure the safety of the work. As with an adequately thick homogeneous layer covering the entire base or at interlifts of the dam, or when being constructed in French drains as finger drains directly placed into the structure during construction, it is not always feasible to set-up a granular drainage system. The granular material can be unavailable or expensive on the site and therefore might make its use impossible or financially irrelevant. This is where geosynthetic solutions offer a valuable alternative. However, two problems arise:
• The extreme loads to which these materials are exposed to, which for most of them will lose their drainage properties because of the creep effect.
• The large quantity of very fine particles in the material itself, which can lead to rapid clogging of the geotextile fibres and thus lead to a complete loss of its permeability, and by extension their efficiency.
The particularity of Multi-Linear Drainage Geocomposites (MDLG) is that they resist particularly well to the load, even extreme, once they are confined, and their manufacturing process allows the selection of geotextiles previously tested to be compatible with the materials placed in contact with them. Therefore, creep and clogging are no longer an issue and those manufactured products offer a stable cost year after year, making easier investment management.
This paper presents, through case studies, the different applications where these materials are particularly efficient, the strategies implemented for their characterisation, and the techniques implemented for their efficient installation and use.

of strategic, critical, and precious metal remain in the tailings – often trapped within the pyrite matrices. These potentially acid generating tailings may require ongoing, in perpetuity, management. Acidic drainage from such tailings often mobilises metals that, if released to the downstream receiving environment, may be of concern to broader stakeholders. Such mines are complicated to permit, and external stakeholders raise questions about the post-closure management of the potential environmental liability.
Following years of research, the EnviroGold Global team has developed a process to profitably recover precious, strategic, and critical metals from live tailings, tailings being reprocessed, or as a stand-alone project to reprocess tailings from a tailings storage facility. This procedure is part of the circular economy using waste for the betterment of society.
Volcanogenic Metal Sulfides Tailings have been studied for many years with various processes being tried to liberate the copper, zinc, gold, and silver from the tailings. More recently, EnviroGold Global completed an evaluation of VMS tailings – in which it was found that the gold was submicroscopic in size. EnviroGold Global then developed a process that uses a catalysing acid to start the reaction to break apart the various pyrite species within the tailings. The resulting reaction, which takes place at about 85°C and at atmospheric pressure, is further catalysed by the sulfuric acid and powerful ferric ion (Fe3+) oxidant produced. Following the initial reaction, the residue containing the gold and silver is separated from the acid. The residue is washed, and the gold and silver recovered by conventional leaching. The zinc and copper can then be recovered from the acid via a combination of solvent extraction and ion exchange resins, widely used in the industry.
The history of the study along with the experimental results and pre-pilot plant testing data will be presented. The initial assessment of the process indicates that it is widely applicable to VMS ores and can be used as ad-on technology for processing plants in a similar way that the INCO SO2 process is used for CN destruction. The process recovers metals and reduces the overall environmental liability of VMS ores making permitting easier and closure less costly.