WATER MANAGEMENT
There are also new ways of looking at desalination . Miners are looking at investing in desalination plants that will supply water to populated areas up to 100 km inland , but in exchange those communities could allow the mines to use inland groundwater . These plans are being called virtual water swaps and are being developed not only in Chile but also in Australia , South Africa and elsewhere . The stumbling block here can be legal complexities to allow for it .
Mining desalination is not all about Chile – it may have the biggest and most costly projects – but Fleming said looking at a world map , most mining desalination plants are smaller and outside of Chile . These range from a desalination plant in the Port of Durban with much of the water used to wash the conveyors , pipelines and railcars at the port and recover any remaining fines , to Areva ’ s port desalination plant in Namibia , to desalination systems for copper and gold recovery in electrolytic reduction and electrowinning operations in Australia and Africa .
Desalination isn ’ t just about arid regions either . Many of the original desalination plants in mining were built to serve solvent extraction / electrowinning plants where the electrolytic cells need ultrapure water . And in mine waste management there is also a push to remove water from tailings and recover that water along with reuse of process plant water . “ Ultimately as the reuse and recycle technology in water advances , in many cases you will also eliminate any need for desal in the first place . For new mining projects , recycling and reuse is now normally top of the list with desal further down the decision tree as a last resort . Golder and others are actively developing process technologies to make water reuse more efficient .”
As a last note on water treatment in mining Fleming cautioned that unlike other industries that also utilise desalination , no two mining projects are exactly the same . Even for the same commodity in the same country the variations in mineralogy means the approach to water can never just be replicated between sites .
Golder at Alumbrera
Looking at an example of the role of water management in tailings before and post mine closure , since 2010 Golder has been providing support in the analysis and design for the closure of the Bajo de Alumbrera tailings and waste rock facilities , a copper , gold , and molybdenum deposit developed by means of open-pit mining between 1997 and 2017 . Operated by Glencore , Minera Alumbrera is in Argentina , 1,100km NW of the city of Buenos Aires in the northwest of the province of Catamarca . It is at an altitude of 2,600 m above sea level . During the past 10 years Golder has performed the following : n Engineering of the cover system n Engineering design of rainwater runoff discharge and containment systems n Water balances n Hydrology assessments n Hydrogeochemical assessments n Design , construction and hydrogeological modelling of pilot scale waste rock and tailings cover cells . The site is currently on stand-by and in the process of the implementation of its closure plan . Golder is carrying out the detailed design for the surface water management system and hydrogeological 1D and 2D modelling as part of the mine closure plan for waste rock facilities in Bajo de la Alumbrera and Bajo el Durazno area . This is based on up-to-date data measured from the pilot cells to confirm and / or optimise cover depths . Since Bajo el Durazno area had not been previously studied , the team is developing an analysis of alternatives to carry out detailed engineering of the defined water management works in the future .
Based on these studies , Golder will provide Alumbrera with the detailed design for the works that will enable the capture , canalisation , and proper disposal of the runoff from basins contributing to the waste rock areas . Furthermore , the works will address the containment and evaporation of eventual seepage from waste rock facilities . In this way , Golder says it is supporting Alumbrera shareholders ( Glencore , Newmont and Yamana ) to mitigate the risks and liabilities associated with the closed Alumbrera mine .
Evoqua – full lifecycle water partner
A major part of success in the mining water space is scope of offering tied in with experience . IM spoke to Patrick Regan , Vice President , Global Power & Mining Markets at Evoqua Water Technologies : “ Our involvement in mining industry water management I would say is high level – we are about unlocking water supply and compliance . Sometimes those two go hand in hand – compliance might be something as simple as TSS or suspended solids levels being higher than permitted or the pH is not where it is supposed to be . It ’ s never an easy fix as mines have a limited lifecycle , plus their focus may change or move . We are working with a major coal mining customer in Canada that is shifting the focus of their operations and need to have a plan in place . We are working with them to determine what assets are needed on the ground to get TSS and pH in line . Selenium is also a specific issue due to it being in the strata they are looking to mine .”
Regan said Evoqua ’ s ideal approach is not only to provide ‘ what goes in the box ’ with regard to water treatment , but to work with the miner to
Evoqua owned Frontier Water Systems handles challenges facing the mining industry through a prefabricated , efficient , advanced bioreactor treatment solution
help them understand what the total life of mine cost will be and to partner with them through the permitting process . And it isn ’ t always about new projects - a water treatment system may also have been in place for years , but because regulations have changed or the watershed has changed , the mine may have to work with Evoqua to implement adjustments .
The company works across the water management value chain – it has good relationships with the engineering houses . But its preference is also to maintain a close relationship with the end user as well . “ We want to make sure we understand the needs and objectives of everyone involved .”
Has the water management market in mining changed ? Regan says : “ The sophisticated miners are now thinking from the very start of a project about the impact of water both from the supply and discharge side throughout the life of the mine .” Mark Owens , Evoqua Field Sales Representative adds : “ In the southwest US it is very much about water scarcity . Miners are much more aware of the need to be a good neighbour in terms of water . One of the mines I am working with has an in-situ mining project . After the mining process , they have to rinse the wellfield and then prove to the local agencies that the water quality is as good if not better than it was . We have designed a modular solution for them . These plug-and-play options are becoming more important as a fixed plant is not always needed once a particular water issue has been resolved . Modular water treatment solutions are also a way for miners to trial a process before committing to a fixed plant capital purchase . Lastly , mines often need a quick response for an immediate water issue that needs addressing , so mobile is a good solution when rapid deployment is required .”
In North America , one of Evoqua ’ s advantages versus others in the sector is the breadth of its mobile “ toolkit ” in terms of the number and variety of its mobile water treatment trailers . Evoqua can deploy a range of technologies to remove solids or salts from a TSS or TDS standpoint and has options for specialty projects like selenium removal . Regan adds : “ And it isn ’ t
42 International Mining | MARCH 2021