WATER MANAGEMENT & TREATMENT
increases the requirements for resins regeneration , resulting in an increase of the volume of waste to reject . This approach is therefore good on low nitrates and sulphates concentrations mine effluents . n Chemical reduction with zero-valent iron ( ZVI ) aims at the chemical reduction of selenates to selenites using ZVI iron . The selenite is then co-precipitated on iron hydroxide flocs . However , ZVI iron will also reduce nitrates to nitrites , leading to both increase in the ZVI consumption and nitrites production , a byproduct toxic to many fish species . ZVI oxidizes to ferrous iron , producing an effluent containing high soluble iron concentration , which is toxic as well and needs to be removed before discharge . n Biological treatment systems are based on microbial reduction of selenates and selenites to elemental selenium . Elemental selenium is insoluble in water and can be removed using a solids separation system to produce a selenium-free water . Veolia adds : “ Biological reduction is by far the most common selenium treatment process and several biological processes for selenium reduction are available . There are , however , a few considerations that should be considered with biological selenium reduction . Nitrates compete with selenites and selenates ; it should be removed prior to selenium reduction to optimise the biological reaction . Elemental selenium particles are difficult to separate due to their size and lack of charge . It is also easily oxidisable , which make sludge disposal complicated as to prevent selenium release over time ; reaction kinetics are slow , which translates into large reactors and hence high costs .”
It continues : “ In addition , due to the low selenium concentration targeted at the effluent , the reductive conditions in the biological system are as such that the transformation of selenates to elemental selenium can lead to the formation of selenide , notably due to longest retention time and in the attempt to transform very low concentrations to elemental selenium . Selenide is a known precursor to organo-selenium species .”
Veolia like BQE Water points out that the issue of selenium toxicity is complex . “ In recent years a number of large-scale bird mortality incidents have been associated with selenium . Examples include birds feeding and nesting at the Kesterson Reservoir in the San Joaquin Valley , CA ( 1983-1985 ), eared grebes at the Salton Sea , CA ( 1992 ) and , again , eared grebes at the Great Salt Lake , UT ( 2011 ). While selenium has been
Xylem & Evoqua create leading pure play water company
In May 2023 , Xylem Inc completed its acquisition of Evoqua Water Technologies Corp , a leader in mission-critical water treatment solutions and services . The combination created the world ’ s most advanced platform of capabilities to address customers ’ and communities ’ critical water challenges . Key markets include mining , and IM caught up with Ken Albaugh , Director of Sales and Services at Xylem , about the strengths and significance of the combination
Q What does the combination of Xylem and Evoqua bring to mining in terms of a combined and comprehensive offering ? A Mine operations rarely fit a mould , each having unique challenges . One constant , however , is that effective water management is critical to operational success and environmental stewardship . This requires diverse , flexible solutions . The combination of Xylem and Evoqua meets this need , bringing a comprehensive suite of solutions to enable the mining sector to manage the full cycle of water challenges . Our team has a wealth of mining expertise and experience in moving and treating water which enables us to create bespoke solutions for every customer challenge . While solutions vary in purpose and scope depending on the requirements of a mine , one common goal is compliance . From managing mine water runoff to feed water , we can provide holistic solutions to ensure that discharge back into the environment will meet or exceed requirements , maximising operational uptime and reducing the risk of fines . Our comprehensive offering reduces the complexity of managing multiple vendors and technologies and leads to a more streamlined , solutions-focused delivery through a single point of contact . We can even offer mobile solutions for water movement and treatment for temporary projects during construction or repairs . supporting its copper ore processing operation . Our system treats the low pH wastewater and ensures the water quality is returned to its natural state , using a combination of dewatering capabilities and treatment solutions . These integrated solutions are commonly requested by our customers to manage the physical movement of water at mining sites and treat it to ensure water quality and compliance . Some customers require more complex or customised dewatering / treatment combinations and through our combined platform , we can meet those needs .
Q With the even greater mining industry focus on tackling tailings challenges , is this an area where both Xylem and Evoqua can bring different approaches to bear ? A Regarding tailings management , our focus is primarily on ensuring environmental compliance through water treatment solutions , which might involve treating runoff water or managing the discharge of excess water into natural water bodies to ensure it meets regulatory requirements . For instance , when a tailings dam is closed , Xylem can now bring an end-to-end solution to move , treat , and discharge water to meet environmental compliance standards . While we are not directly involved in tailings processing , Xylem provides equipment that can be part of a broader tailings management solution , including the use of filter presses and the pressing of tailings into a cake form , which is a method of dry stacking . This approach reduces the environmental impact of tailings storage by minimising the need for large tailings dams and the associated risks .
Q Are there any specific examples of where Evoqua water treatment technology could potentially be combined with Xylem dewatering solutions for example as a complementary offering ? A Our customers now have access to a complete offering that can help them meet environmental compliance and operational efficiency goals , in tandem . For example , in a quarry project on the west coast of the US , we combine market-leading dewatering technology to pump water with a best-in-class treatment system . Water is treated before it is discharged back into the environment to ensure compliance with permit requirements . Also in the western US , we are onsite at an in-situ mine
The combination of Xylem and Evoqua has created a unique integrated offering of water solutions for mining
26 International Mining | MARCH 2024