Anglo American Thermal Coal’s (AATC’s) New Vaal operation, in the Free State, recently formed a steering committee with State-owned power utility Eskom to implement a freeze-crystallisation facility to treat brine produced by its mobile water treatment plants.

Brine is a by-product of the desalination pro- cess used by the mine’s mobile water treat-ment plants. The freeze-crystallisation facil-ity, which is expected to ramp up to full production by July 2014, will remove 40 t of salt from the system daily.

“To create a zero liquid-discharge waste stream at the end of the water treatment pro-cess, a final step is needed to remove the final liquid in the brine. There are various methods that can achieve this; however, the New Vaal colliery piloted the freeze-crystallisation technology on site and found it to be effective,” AATC tells Mining Weekly.

Once the brine treatment technology has been proven, the company will implement the next stage, which involves investigating the possibility of using the salt produced as a marketable product in the fertiliser and industrial explosives industry.

AATC installed the two mobile water treatment plants, with a combined capacity to treat 24 Mℓ/d of mine-affected water, in October 2010.

“Although the plants use a different technol-ogy, the process flow is much the same. During the filtration stage, suspended material is removed from the water, after which the water is subject to the reverse-osmosis stage, where it is pushed through membranes at high pressures. This removes the dissolved salts from the water, leaving you with the final product water,” AATC explains.

Currently, the water is treated to the specifi-cations of the Lethabo power station, in the Free State, with the entire volume of treated water being taken up by the station, where it is used in its cooling towers. The water that New Vaal provides replaces water that would otherwise have been extracted from the Vaal river, says AATC.

“Before the water treatment plants were installed, New Vaal optimised the use of mine water in al its processes, such as the coal processing plant. A portion of the water was also provided for the Lethabo power station, with the remainder stored in pollution-control dams.”

Former New Vaal GM Johan van Schalkwyk says that the company is committed to effecting sustainable progress in the treatment of mine water.
“Anglo American aims to mine in an environmentally responsible manner and we have clearly stated our commitment to efficient water management. Hence, we are proud of the achievements of New Vaal in implementing a lasting solution to its excess-water challenges. Moving forward, our company will remain a recognised leader in investigating treatment technologies, developing infrastructure and partnering with our water stakeholders,” he concludes.