Ozone treatment of mining effluents

A method of treating mining effluents, the method comprising:

• providing mining effluents containing at least one nitrogenated compound selected from the contaminant group consisting of:
• ammoniacal nitrogen, nitrite ions, nitrate ions, thiocyanate ions, weak acid dissociable cyanide ions and cyanide ions, the mining effluents further containing cyanate ions;
• performing a first ozone treatment on the mining effluents;
• performing a second ozone treatment on the mining effluents after the first ozone treatment;
• and
• adding an alkaline chemical to the mining effluent between the first and second ozone treatments;
• wherein the first and second ozone treatments are performed respectively at first and second pH, wherein the second ozone treatment is performed at a higher pH than the first ozone treatment, wherein the first pH is larger than 6.5 and smaller than 8.5 and wherein the second pH is larger than 8.5 and smaller than 10.5;
• wherein the first and second treatments together reduce a concentration of the at least one nitrogenated compound in the mining effluents.