Reverse osmosis (RO) technology is a common method used for treating effluent on mines but low recoveries can increase costs, leading to the need for more effective and fit-for-purpose solutions.
Multotec Process Equipment explains that RO was initially designed to remove monovalent salt molecules from sea water but that wastewater on mines also includes divalent and trivalent elements, which cause scaling of membranes in RO systems. Standalone RO plants used to treat mine water are often operated at lower recoveries, to increase the lifespan of the membranes. This results in large volumes of highly concentrated brine streams, which are either recirculated within the system or require expensive effluent treatment systems. To address these challenges, Multotec offers niche technologies that are suited to treat divalent and trivalent elements in water on mines.
The company has partnered with Clean TeQ Water in Australia, to offer continuous counter current ion exchange technology to mines across Africa. The technology uses resin, which is more selective, to extract larger molecules and is designed to achieve high recoveries of over 90%, so that process water can be re-used within the mine’s process circuits or discharged safely to the environment. The resin-based chemistry removes target species, selectively extracting contaminants through exchanging ionic functional groups that are engineered on the resin beads.
Clean TeQ’s ‘moving bed’ solution is seen as ground-breaking technology that is able to unlock the potential of resin chemistry. In contrast to conventional fixed-bed systems, the use of resin transfer mechanisms allows the continuous ionic filtration to handle up to 150 ppm of solids, whereas conventional systems need a 100% clean liquor. Total suspended solids and total dissolved solids can therefore be simultaneously removed.
It also optimises the inventory of resin, a significant cost contributor to the overall plant, and provides high water recoveries. Other benefits include its low power consumption and its ability to recover valuable trace metals as a by-product.
The continuous counter current ion exchange solution is supplied to the African market by Multotec.