Continuous measurement of sulfate to optimize mine water desalination with real-time augmented in-situ raman spectroscopy

Mineral extraction is uniquely complex in its water portfolio, with companies often balancing limiting freshwater intake and environmental discharges simultaneously. Closing the loop on the mine water cycle is difficult with streams of variable quality, and desalination technologies are increasingly required to improve water quality for downstream use or environmentally acceptable discharge. Management of these nanofiltration or reverse osmosis processes requires real-time insight into water profiles, which range from brackish to saline, to mitigate scaling events, particularly on mine process wastewater. Frequent changes in upstream processes disrupt reverse osmosis operation, and real-time, continuous water quality monitoring can provide immediate feedback to allow for proactive adjustment of chemical dosing, maintenance intervals, and operational setpoints to protect membrane life and maintain process uptime.

We propose real-time Augmented in-Situ Raman Spectroscopy (AISRAS) – a technology leveraging machine learning in conjunction with Raman spectroscopy – to continuously monitor water constituents. In a pilot test, we measured sulfate in a full-scale operational reverse osmosis facility receiving mine process wastewater in a Western African location for over one year. We provided real-time feedback from four different measurement points to directly optimize membrane treatment operations. AISRAS operated well below a 10 % deviation margin compared to laboratory grab sample analysis. Furthermore, laboratory sulfate estimations do not provide the necessary temporal resolution to precisely identify sudden change points in the water matrix. We show that by directly measuring sulfate in-situ, preventative prediction of membrane scaling of calcium sulfate could be achieved.