MINE WATER MANAGEMENT
their water management appears to be
increasing. With the increasing stringency of
discharge permits, advanced technologies and
regulators demanding that a WTP is online before
any mining activity commences, the value of
efficient and expert execution has become paramount.
Fighting calcium sulphate
A North American multi-metal mining operation
began experiencing severe, tenacious calcium
sulphate deposition in its leaching operation
shortly after coming on-line. It was reconfigured
to incorporate a thickener as an additional
clarifier to reduce scale formation and promote
precipitation of calcium sulphate.
Calcium sulphate deposition at the mine site
was difficult to address because the process
water pH was highly acidic, typically 1-2. Many
deposit control chemistries are ineffective at this
low pH.
The low pH and use of seawater for process
water also made assessment of antiscalant
program performance difficult. Low pH is
corrosive to mild steel, and seawater is corrosive
to stainless steel, making it difficult to use
traditional scale coupons to monitor the results
of deposit control programs.
The thickener reconfiguration resulted in a
copper production loss of some 6%. The mine
lost additional productivity from reduced flows
and periodic cleaning shutdowns due to scale
build up in the process lines and equipment.
The mine wanted to reduce or eliminate scale
formation in the leach circuit and be able to
monitor program performance.
ChemTreat laboratory and technical personnel
worked with the mine’s metallurgical group to
screen potential antiscalants, leading to the
development of ChemTreat ML708 scale and
deposit control agent. ChemTreat then designed
and fabricated scale coupons made of titanium
and fibreglass that were effective at low pH and
in seawater. Finally, ChemTreat developed a pilot
unit that assessed the process water flow and
scale formation both before and after the
injection of ChemTreat ML708 to validate the
antiscalant program’s performance.
Baseline data prior to the ML708 antiscalant
addition revealed a calcium loss of 2.5% through
the leach circuit, which translated to a daily
precipitation of approximately 2 t of calcium
sulphate. The coupons also showed rapid scale
build up. Application of ChemTreat ML708,
however, consistently kept the calcium in
solution throughout the circuit, as evidenced by
clean coupons and the mine’s ability to operate
without interruption during the initial month-long
program evaluation.
The pilot unit also verified the efficacy of
ML708 in preventing scale formation.
ChemTreat ML708 proved effective in inhibiting
46 International Mining | MARCH 2018
calcium sulphate
scale formation under
the acidic and highly-
ionic conditions of the
mine’s process water.
Its unique chemistry
allows it to function in
operations where
commonly-used
antiscalant polymers
show limited or no
success in controlling
scale because of low
pH or high brine
strength.
ChemTreat designed and built retractable
titanium and fibreglass scale coupons. Calcium
analyses performed by the mine’s laboratory
validated the antiscalant program’s ability to
maintain calcium concentration across the leach
circuit. The ChemTreat team met the mine’s
objectives to reduce calcium scale in their
operation and monitor and validate the
performance of the program.
Maximising membrane plant
efficiency
Genesys International is also at the forefront of
fighting calcium sulphate and other scale
deposits, but specifically in reverse osmosis and
nanofiltration membrane plants fed with mine
water.
Membrane technology is being adopted widely
by mines, both to clean up and reuse wastewater
and to concentrate metals for enhanced recovery.
There are now more than 300 membrane plants
treating mine water around the world.
In 2017, Genesys won a £500,000 research
grant from Innovate UK – a UK Government
industrial initiative – specifically to fund
investigations into the scaling that affects
membrane plants used to manage mine water
and how to tackle it.
Genesys first started looking seriously into
how its products could help in the mining
industry back in 2012, when the company
discovered that large orders for one of its
products from Peru were being used at gold
mines. Mine operators had chosen Genesys
Calcium Sulphate Antiscala nt (CAS) based on
independent studies, which had shown it was the
most effective product for inhibiting calcium
sulphate scale from reverse osmosis membranes.
Fernando del Vigo of Genesys Spain paid
several visits to the Peruvian mines to monitor
and optimise their antiscalant use and conduct
membrane autopsies and cleaning tests.
The sheer volume of Genesys CAS orders from
various countries prompted MD, Steve Chesters,
to investigate further, and he discovered that
products were already being used at mines
With the help of an Innovate UK grant, Genesys
has developed mine water scaling prediction
software specific to the mining industry. The
funding is also helping it rewrite the chemistry
book for the extremes of pH and scale formation
that occur in mining applications. Here testing is
underway in a pilot plant rig
around the world. So, in 2016 Genesys took the
step of employing Phil Morton as Mining
Manager. He had previously worked at Glencore’s
Mount Isa mines and Barrick’s joint venture mine
in Saudi Arabia.
“The complexity of mining water chemistry
means each mine and reverse osmosis
membrane plant has different requirements,”
says Morton. “Because Genesys is uniquely set
up to conduct membrane autopsies and run
scaling tests, we can formulate site-specific
antiscalants for any mine in the world.”
Max Fazel, Senior Research Chemist at the
Genesys R&D centre in the UK, has been
conducting a series of tests and experiments to
gain greater understanding of calcium sulphate
solubility in various conditions. “The solubility of
calcium sulphate is very different at acidic pH
than at alkaline or neutral pH,” he explains. “This
means we need to formulate, test and prove
specific antiscalants for use in membrane
systems in situations where calcium sulphate
scale is a problem.”
Genesys has already developed tailored
products for different mines in Peru and has
recently specially created one for a mine in
Australia which suffers from high levels of barium
and silica scaling.
“Conventional reverse osmosis antiscalants
simply don’t work at these extremes,” says
Chesters. “With the new products and software
we’re developing, we’re optimistic that we can
help to make reverse osmosis a viable option for
more mines, enabling them to clean up dirty water
and extract precious metals more efficiently.”
Morton adds, “Our research has made it clear
that no single product would work for all mine
waters. They are as unique and changeable as
the orebodies being mined. Running synthesised