WATER MANAGEMENT & TREATMENT
To get the big picture on water management trends in mining, Paul Moore
spoke to Andrew Watson, VP of Stantec’s global mining business, who has
20 years of experience in the design and construction dams, tailing
storage, heap leach, waste containment facilities, and water management
systems
Q As a major water solutions company are you seeing mining companies
becoming more serious about implementing water treatment and water
management at an early planning stage, despite the added investment
costs?
A Yes! Water is still the catalyst for challenges to permits so companies
developing projects are focusing on water supply, management and
treatment. We are seeing increased attention on water quality, both water
going in and coming out of the mine, and more careful accounting of the
water circuit, ie where the water is and where it goes. We are all more
aware of variability in rainfall, challenges to traditional supplies and the
economic cost of running out of water. Some projects face melting
glaciers that might contribute more water than planned. Other projects
face changing weather patterns that result in peak seasonal flows – flows
not previously experienced. There is more interest in managing potential
impacts so as not to generate poor quality water. Finally, we’re seeing a
fair amount of focus on balancing flows so as to have smaller treatment
plants, and so on. Investors also want to know more — the prospect of
potentially treating water forever is scary. As a result, potential impacts to
water and water use are discussed in greater detail in feasibility studies,
permit applications and in board room decision making.
Q Is the greater focus on getting water management right being driven by
water shortages, a more sustainable mining culture, local community
pressures or all of these?
A We are definitely seeing more focus on getting water management right
– this is driven by all of the above. Some miners in Chile and Peru are
forecasting lower than expected production due to water shortages. Other
mines are making bold commitments to cease extracting groundwater –
this will certainly put mining in a favourable light with respect to fairly
sharing scarce water resources. More and more we see miners forgoing
the use of fresh water and using water the community has already used –
like capturing sewage and industrial wastewater for reuse at the mine.
Solutions like these make economic sense – moving water around is
expensive, so using less is good for business. When metal prices were
low, miners looked for savings in every part of their operations –
including in their water circuits. These cost saving efforts have led directly
to looking after litres. The commitments, by the big miners, to be good
citizens have set an expectation with respect to sustainable mining
practices and sharing water with communities. And yes, we see this
consists of multimedia and carbon filtration
followed by primary Reverse Osmosis and reject
recovery Reverse Osmosis.
Mobile water treatment
South African water specialist Talbot Consulting
Services has launched a state-of-the-art mobile unit
that enables mining and mineral resources players
to test a highly efficient and cost-effective water
treatment and mineral product recovery solution,
right on site. The mobile unit with its fully-equipped
test laboratory gives clients a clear demonstration
of the effectiveness of Vibrating Sheer Enhanced
Process (VSEP) technology, a solution developed by
30 International Mining | MARCH 2020
message embraced by the
individual operations and a
resulting attention to water
management and progress
reporting. Many mines have
the neighbouring communities
participate in their water
monitoring programs and are
quite transparent about what
they use and discharge.
Q What about long-established
operations – are more and
more operators looking to “retrofit” water treatment into mining
complexes despite limited remaining mine life?
A Yes, retrofits are needed when operations are nearing the end of their
mine plan or undergoing a shift to the production rate, process or water
balance. Water treatment – to enable discharging – is often needed to re-
equilibrate the system. The practice of using a tailings facility to store
excess water is under scrutiny and as miners draw down those ponds the
excess water must be treated and discharged or additional water storage
capacity must be built. In the case of Chile, for example, some mines are
starting a new life by transitioning from an oxide leach to a sulphide
milling operation, and the additional water needed will be provided by sea
water rather than drawing from ground or surface water.
Q With notable wet tailings dam failures, is the greater focus on using dry
stack tailings and paste tailings affecting the whole water ecosystem
approach by mining companies?
A Certainly, there is more interest in alternatives to address some of the
risks posed by the TSF. In Brazil new regulations are driving a flurry of
measures to retrofit dams that don’t meet current standards. Some of
these measures will be adopted in the industry, if they add value. The
industry is looking hard for alternative ways to safely store tailings and
equipment manufacturers continue to invest in research and development
of bigger and more efficient filters. At the same time mineral processing
specialists are working with miners to develop separation technologies
that use less water. Coarse particle flotation might help some mines break
the trend towards finer and finer tailings – fine tailings use more water
and coarse tailings are easier to drain – so having a coarser tailings
stream would save energy (and money) on grinding and lead to a stronger
TSFs. The TSF is still the most significant variable in the water-
management equation. The drive to improve tailings safety adds to the
effort miners are making to improve mine water management. This will be
an exciting decade.
US company New Logic Research Inc.
This solution not only treats highly
contaminated and difficult water streams to
municipal quality but is able to recover valuable
product from residue that would otherwise be
consigned to waste. “VSEP achieves in a single
stage what traditional reverse osmosis solutions
typically cannot accomplish even with significant
pretreatment. Often piloted as a last resort on very
contaminated streams, VSEP is typically the most
effective, simple and easy to operate.” says Talbot
General Manager Claire Lipsett.
The technology adds significant value through
the concentration of brine streams, making it ideal
for sites seeking to defer costs where brine
storage facilities are nearing capacity. Trials at one
Mpumalanga-based coal mine have projected a
50% reduction in daily brine production which
would mitigate the risk of overflow and enable
future expansion. It also substantially enhances
the recovery of high-quality water for use in site
activities, as a substitute for municipal supply or
be taken up by water-stressed local communities.
“Miners and precious metals refineries benefit
from the recovery of large quantities of ultra-fine
particles of product from their waste streams that
can be returned to the process,” Lipsett says. A
number of South African case studies reveal that