Mining Sustainability in Action: Removing arsenic and cyanide with reverse osmosis 

Researchers from ESPOL and Ghent University have evaluated two methods for treating highly contaminated wastewater mining effluents generated during gold cyanidation in the mining industry: a conventional physico-chemical treatment and a reverse osmosis (RO) system. This innovative study was carried out at the mining company, where the treatment plant was installed and operated for approximately five weeks. During this period, water samples were collected three times a day to analyze critical parameters such as pH, total dissolved solids (TDS), and electrical conductivity (EC). In addition, analyses of ions, total organic and inorganic carbon, total arsenic (AsTOTAL), total cyanide (CNTOTAL), and heavy metals as copper, iron, manganese, zinc, chromium, and lead were performed. 

The conventional physico-chemical treatment proved to be effective in reducing the organic carbon load, achieving a 79% removal efficiency. However, this method failed to remove arsenic and cyanide concentrations from the mining wastewater effluent. AsTOTAL levels after treatment remained between 0.2 and 0.3 mg/L, and CNTOTAL concentrations varied between 110 and 1620 mg/L, clearly above the maximum allowable environmental standards. 

This is where reverse osmosis changed the game. Using a BW30 membrane, the pilot-scale RO system achieved removal rates close to 99% for both contaminants. As a result, AsTOTAL concentrations were reduced to less than 80 μg/L, and CNTOTAL to less than 0.9 mg/L, meeting regulatory requirements for effluent discharge. 

This study not only highlights the effectiveness of reverse osmosis in removing persistent contaminants but also emphasizes its potential to transform sustainability within the mining industry. By directly comparing both methods under real operational conditions, the data obtained from rigorous sampling and analysis demonstrated that reverse osmosis not only reduces contaminants to safe levels but also provides a viable and scalable solution for mining operations seeking to improve their environmental performance. 

In conclusion, reverse osmosis has proven to be advantageous to conventional physico-chemical treatment in the removal of specific contaminants and in meeting environmental standards. The deployment of RO systems in the treatment of mining effluents can be a crucial step towards environmental protection and the adoption of more responsible and sustainable practices in the mining industry.