WATER MANAGEMENT & TREATMENT
that ’ s stored inside , clean the water and restore the land . The relationship with CleanTeQ came about due to two Future Element partners – MD and CEO John Carr and Director Pat Walta – previously having worked there and therefore have good familiarity with its technologies . We really felt that some of those technologies can help unlock the value stored in tailings .”
Slattery adds : “ In addition to the ATA dewatering technology we like the CLEAN-IX technology for metal extraction which works well for recovery of metals in low concentration . That said , we are technology agnostic ; we realise that every tailings dam is different with unique mineralogy – you are going to need a toolkit of different technologies to be able to solve these problems . The relationship with CleanTeQ is a good start , dewatering is a massive challenge and ATA is an amazing technology – the fact that it can dewater tailings under its own weight without mechanical compression is very interesting to clients – evidenced by the testwork program we recently announced relating to BHP . Once you dewater and move to a dry stack situation , I think that opens up a lot of different options around tailings valorisation – and removing wet tailings facilities .”
On the BHP testwork , he adds : “ We are focused on their South Australian copper business and will deliver a proof of concept for them with ATA , based on that will evaluate the commercial merits of a wider rollout . This work will be on existing tailings dam facility , but obviously , as new mines come online then you can design in dry stack tailings at the outset which means you aren ’ t spending millions or billions in capital building or raising dams .”
On its go-to-market approach , he says Future Element is engaging directly with mining companies on what it calls ‘ economic rehabilitation .’ “ This includes providing a service model to reprocess their current and historical tailings . We are developing partnerships with other technology and engineering firms but nothing I can disclose yet . Our main focus is bringing projects into operation , working with miners on joint ventures or using BOO / BOOT models where we reprocess the tailings for them for a fee . This helps them to eliminate wet dams and in the process , reduce closure costs , clean the water and ultimately return the land .
In terms of its depth of capability , Slattery also mentioned the team ’ s collective experience from New Century Resources . “ It was a major open pit lead-zinc mine that operated from 1999 to 2015 , producing about 1 Mt / y of zinc concentrate as the third largest zinc mine in the world . At completion of mining , the tailings contained 78.9 Mt . New Century Resources headed by Pat and John acquired the mine in 2017 from MMG and tailings reprocessing commenced in 2018 after an
8-month refurbishment . The process includes 10 Mt / y hydraulic mining of tailings , followed by flotation , producing about 270,000 t / y of zinc concentrate , with reprocessing to be completed by 2027 .”
That story and model really shows Future Element ’ s track record in that space . “ New Century was then sold to Sibanye Stillwater in early 2023 , that freed Pat and John up , along with myself and Dennis Gibson to start Future Element . Through the New Century experience , we have built up an investor base that is interested in tailings remediation projects . It ’ s not about the technologies in isolation , we bring the capital , the technology and operational capability to develop the projects that deliver the desired environmental and financial outcomes for miners .”
Passive treatment methods for AMD
Stantec has been looking at passive treatment of mine waters and IM recently caught up with Guadalupe Fattore , its Chemical and Environmental Engineer - Mine Water Treatment . She states : “ Mineral extraction and processing are potential sources of surface water and groundwater contamination when acid mine drainage ( AMD ) is generated , which may persist after the mine is closed . For treatment of AMD , the most effective and economical water treatment systems will be desired for reclamation of the mine sites . Therefore , passive treatment technologies should be considered for applications where their efficiency has been proven and which have a low cost of operation and maintenance with respect to active treatment systems .”
Passive treatment methods are based on physical , chemical , and biological processes in which the pH and Eh conditions are adjusted . The objective is to enhance the formation of insoluble precipitates and the retention of metal cations , under either oxidising or reducing conditions . The dilemma faced by passive treatment designers is selecting the appropriate technology to treat AMD since it is a sequential process that usually requires various passive technologies installed in series .
The most common passive treatment methods include aerobic wetlands and biochemical reactors ( BCRs ). Less conventional passive treatments involve terraces for iron removal ( IT ) and limestone beds for manganese removal ( MRB ). The primary objectives of these passive technologies are to raise pH , precipitate metals , reduce sulfate concentration , and removal of suspended solids . Designers of such treatment systems face the challenge of selecting the appropriate technology to address AMD .
Typically , passive systems use alkaline materials to neutralise acidity , organic substrates to create reducing conditions , and manure to
introduce bacteria that reduce sulphate to sulphide , which reacts with metals , forming insoluble precipitates .
Fattore recently used four passive treatment technologies for a pilot plant for the treatment of AMD from an abandoned underground mine . The passive treatment system consisted of a terrace for iron removal , a biochemical reactor , an aerobic wetland , and a manganese removal bed . The pilot plant results indicated that the AMD treatment with a circumneutral pH was effective , and the metal concentrations complied with the discharge limits . The only parameter that reported concentrations above the limit was the biochemical oxygen demand .
Fattore comments : “ Passive treatment systems offer an efficient and cost-effective approach for addressing AMD , particularly towards the end of the mine ’ s operational life . When a mine generates AMD , it faces the need for ongoing treatment , that may not be cost effective for the mine . However , in cases where AMD flows are relatively low , passive treatment systems can also be utilised for water management .”
She adds that iron terraces , wetlands , and manganese removal beds are also utilised for metal removal . “ In this particular study , they were incorporated to enhance the efficiency of the BCR , thereby enhancing the overall performance of the passive treatment system . Interestingly , the BCR demonstrated greater efficiency compared to other passive technologies . However , due to the specific oxidising conditions required for manganese removal , an MRB was essential in this passive system .”
The IT , the BCR , and the wetland effectively reduced iron concentrations to levels below the recommended threshold ( 0.5 mg / L ) specified in the Manganese Removal Bed Module Overview , AMDTreat . However , the MRB achieved only 50 % efficiency due to the wetland ’ s incomplete removal of biochemical oxygen demand , resulting in oxygen depletion within the MRB and inadequate water oxygenation .
The effluent from this pilot-scale passive treatment system she says met the specific discharge limits for the site , except for the Biological Oxygen Demand , which was slightly above the limit . However , after approximately six months , when the BCR reached equilibrium , there was a significant decrease in BOD .
She concludes : “ In the design and configuration of the treatment system , terrain topography must be taken into account to ensure gravity flow and proper circulation and distribution of influent within the system . It is essential to maximise hydraulic retention time so that contaminated water comes into contact with the materials used in these passive technologies . Other important aspects to consider include the available land area for construction , flow rate ,
18 International Mining | MARCH 2024