MT MORGAN OPEN CUT PIT WATER QUALITY MODELLING stage 2 ● 9
High lime additions have previously been reported when treating site water from the Mount Morgan open cut pit (OCP) and other seepage waters (Mundic seepage pond), mainly due to the high dissolved aluminium, magnesium and sulphate levels (Minerals, 2021). Heritage Minerals commissioned Green Gold Technology (GreenGold) to conduct a laboratory water treatment test program (Minerals, 2021). The initial OCP water treatment tests using commercially available lime/limestone were done during August 2019 and February 2020. A process flowchart of the Mount Morgan tailings recycling process is presented in Figure 1-2. There are four steps in this recycling process: Step 1: Cyanide leach, Step 2: RIL contact #1, Step 3: RIL contact #2, Step 4: RIL contact #3. The leach slurry has a pH of 10.0 to 10.5, however after recovering the free cyanide and copper in the CIL tailings, the final ReCYN tailings is expected to have a pH of 9.6. The ReCYN discharge slurry going to tails is expected to contain 35% w/w solids. 136 m 3 /hr (or 2,977 m 3 /day) of OCP water required as a significant portion of the process water is recycled internally using the final tails thickener.
Figure 1-1 Location of the Mount Morgan Open Cut Pit (OCP)
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