MINE WATER MANAGEMENT
An increasingly precious resource
Innovation in water management is vitally important and new technology applications are essential, as John Chadwick reports
Like so many responsible mining companies, Barrick recognises that water is a shared, vital and, in many places, scarce resource and says this is“ why the company strives to use only what it needs and reduce its impact on other water users in the communities in which Barrick operates. As the company mines in increasingly remote areas with wide variations in climate and access to water, Barrick has worked hard to find new ways to meet water challenges. This is not only the responsible thing to do, it makes good business sense and it is consistent with the company’ s core values.”
Last year, Barrick implemented a new water management strategy to ensure it has the right talent, the right plans and the right resources in place to effectively manage water-related risks at all the company’ s sites. Water management is being integrated into life-of-mine planning in a systematic way, and the water management team is working closely with operations and the company’ s digital transformation team to integrate technology into all water management processes. The long-term goal is to develop successful site-based water stewardship that brings value to the company while protecting people, partners and the environment.
The development and implementation of the water management strategy is being overseen by Vice President of Water Management John McCartney.“ It’ s about more than just compliance, water stewardship,” says McCartney,“ it’ s about genuinely caring for something that is vital to everyone in the community.”
Chris Biederman, Senior Water Process Engineer & Technology Development Lead, Water with Hatch reminds us all that“ without ready access to [ water ], ore processing and mineral production becomes prohibitively expensive, or is altogether impossible. Even when water is easily available, stakeholders expect that it will be used efficiently and sustainably by miners in return for being granted a social license to operate.”
He advises that“ direct recycling of water from a TMF without treatment is preferred, given the large volumes of water in circulation. If treatment is required, steps should be taken to decrease water usage as much as possible and to optimise water treatment systems to manage operating costs. Bench-scale testing is one tool that can achieve this objective. Smart application of bench-scale testing is a costeffective way to evaluate various technologies in support of new capital projects, or troubleshoot and optimise existing treatment systems. Bench-scale investigations should not replace long-term pilot programs at scale; instead, bench-scale tests should be viewed as complementary and used to inform the piloting phase.
“ Test at the source. When dealing with complex mine waters, variations in water quality often occur. These variations may be seasonal – for example, an increase in turbidity due to runoff – or they can be process-related and result in significant changes to water quality in a short timeframe. Testing should be conducted in the field to get the most applicable results. This way, changes to water chemistry that result from shipping samples off-site and sample storage conditions are eliminated. This is particularly important for water that may be saturated with dissolved salts, where fluctuations in temperature can cause precipitation to occur prior to testing.
Barrick first assesses its water-related risks and water conservation opportunities through rigorous analysis. Water stewardship will be integrated into life-of-mine planning in a systematic way, factoring in considerations like long-term water balance and cumulative impacts. The company aims to“ responsibly manage water resources by updating our standards, guidelines, assurance reviews and audits to mitigate our risks and continuously improve our performance. Though every site has distinct characteristics and circumstances, these procedures provide consistency to our assessment and assurance processes. At its core, this follows a simple structure and each site must address a number of key considerations: what are your risks, what is your mitigation plan, what are your resources, how much will it cost to implement your plan, when will it be implemented, and what are the key milestones?”
“ Challenge the status quo. Typically the standard‘ jar test’ method is the go-to for coagulation and flocculation tests. Jar tests are best used to evaluate the performance of a small number of chemicals when precedent exists for treating a particular water stream. Each individual jar test requires one litre of sample, so there are practical limitations to the number of tests that can be performed in a reasonable amount of time for a given water sample. The volume of raw sample required to run numerous jar tests also limits the number of tests that can be reasonably performed.
“ At Hatch, we have successfully developed and applied high-throughput methods to test mining waters and tailings. The methodology involves simultaneous testing of up to 48 treatment conditions using small sample volumes( 15 or 50 millilitre). The result is a very efficient method to screen multiple chemicals, oxidants, or pH conditions, all while minimising the size of the raw water sample required and maximising the number of tests and data collected. This method has proven to be very effective when testing mine waters having complex water chemistry.
“ Respond rapidly. Portable battery-operated instruments for water testing allow for in-field measurements and timely feedback to guide bench-scale tests. Further, water analytics are benefiting from miniaturisation as chip-based sensors are becoming smaller and thus more portable. Innovative solutions are also available for measuring very low concentrations of select contaminants using biological-based sensors. All of this supports the ability to quickly mobilise water-testing equipment and analytical instruments for site-based testing globally.”
Water education
By the year 2030, water demand is expected to exceed sustainable supply by 40 %, but only 42 % of respondents from a survey conducted by Ecolab and GreenBiz Group cited water
MARCH 2018 | International Mining 41