At Sedgman, we understand that our biggest influence on the environmental sustainability of minerals processing in the resources industry is by delivering design solutions that reduce mine site impacts.  

The disposal of tailings is commonly identified as the single most important source of environmental impact for many mining operations. With some recent high-profile failures of tailings dams, governments, environmental groups and mining companies have been looking to implement alternative methods of managing tailings. Avoiding the use of tailings dams altogether or avoiding dam raises can have a significant impact on water recovery and mine site rehabilitation, as well as reducing risks to communities from dam breaches. 

One of our key services is tailings dewatering, which maximises water recovery, and reduces the likelihood of environmental harm associated with tailings dams. Having extensive technical experience in tailings processing systems from coal through to base metals, Sedgman has delivered a significant number of studies and projects which include both a variety of tailings dewatering technologies and a variety of reject transport and emplacement methods.

As an example, Sedgman has delivered an engineering, procurement and construction contract of a new tailings dewatering facility at the Byerwen mine in Queensland. This project will convert the existing wet rejects pumped co-disposal system to a combined dry tailings and coarse reject trucked system. The new system is an integrated element of the Byerwen mine expansion and results in a lower operational risk profile, less power usage and improved water recovery and management of dewatering chemicals.

Sedgman has also recently delivered the Nevada Copper Pumpkin Hollow Project in Nevada, North America, which included plate and frame filters to dewater tailings.

Providing environmentally responsible solutions is key for Sedgman. With the need for more sustainable energy, water and land use in the resources industry, we are pleased to be recognised as providing reliable tailings management solutions. 

Our teams of experts have extensive experience in all aspects of tailings management:

• Test work on dewatering technologies and tailings emplacement characteristics, tailings recovery and scavenging projects
• Design, construction and commissioning of tailings dewatering facilities
• Design, construction and commissioning of tailings transport systems
• Operation of the dewatering and transport facilities
• Work with specialist partners for emplacement area design, and emplacement area management strategy

Mechanical Dewatering

We have designed and installed more than 30 processing plants that include full mechanical dewatering of the tailings.

These have utilised a range of technologies including:

• Belt press filters
• Plate and frame filters
• Horizontal vacuum filters
• Centrifuges

Tailings Transport

Our range of expertise in this area includes:

• Multistage pumping systems for either tailings pumping or co-disposal (coarse and fines) pumping
• Conveying and stacking systems
• Cake spreading systems
• Paste back fill plants

Water Resource Management

A significant portion of mine water resource management use is directly related to tailings volumes and disposal approaches. Sedgman is committed to development of lower water footprint minerals processing designs, though modelling of ore sorting options to reduce tailings volumes, as well as alternate processing and dry tailings options, and management of acid mine drainage risks. 

Many mines operate in areas of high-water stress, and this pressure is likely to grow with the demand for minerals to support electrification and clean energy. Water is a valuable resource, with access to water integral to social, cultural, environmental and economic wellbeing. 

Reducing Water Loss Though Tailings Disposal Design

The solids concentrations achieved on dewatering via thickener vary for different tailings, since particle size distributions, clay mineral content, particle shape, mineralogy, electrostatic forces and flocculant dosing vary considerably.

The per cent solids of tailings can range from 15% for minerals sands slimes to 40-45% for base metals and gold tailings. There is a significant amount of water entrained with tailings being disposed in dams, therefore, which will only increase as grades reduce over coming years.

Reducing net water usage can be achieved by reducing water entrained with tailings and reducing the volume and fineness of tailings.

Sedgman has significant experience in designing lower water footprint tailings options, including:

• Slurry disposal: Tailings are commonly pumped as a slurry in a pipeline and discharged sub-aerially into a surface TSF
• Thickened and paste disposal: Thickening of tailings in the processing plant before disposal enables process water to be recycled directly back to the plant, reducing water losses and reducing plant raw water demand
• Dry stacking: True dry stacking requires that the flocculated tailings be filtered, usually under pressure or possibly under vacuum, to produce a product that is transportable and stackable using ‘dry’ material transportation and disposal techniques
• Co-disposal of coarse wastes and tailings: The co-disposal of the coarse wastes and tailings from a mine provides a means of reducing the volume or footprint required to store the separate waste streams by means of the tailings filling the void space between the coarse wastes
• Integrated disposal of coarse waste and tailings: An integrated mixture of waste rock and paste tailings can potentially be used as a sealing material in covers over potentially contaminating mine wastes

Sedgman has delivered multiple studies and projects in tailings options, including co-disposal, dewatering, dry stacking across a range of commodities and with a variety of technologies including belt press filters, solid bowl centrifuges, plate and frame filters.

Our expert team can review options for your site and support:

• Test work on dewatering technologies and tailings emplacement characteristics
• Design, construction and commissioning of tailings dewatering facilities
• Design, construction and commissioning of tailings transport systems
• Operation of the dewatering and transport facilities

Reducing Water Use Through Alternate Processing Options

Reduction in water entrained with tailings can also be achieved through changes to the minerals processing approach.

Options vary depending on commodity, ore characteristics, and can include:

• Pre-concentration of ores to reduce power consumption and tailings volumes
• Reduced power consumption and coarser tailings through early waste rejection within the processing plant (through improved recovery at coarser grind sizes)
• Heap leaching