Dewatering Discharge Water Treatment Options

In 2020 Dacian identified significant mineralised zones in the Westralia and Jupiter prospects, however, in order to access these deposits significant pit dewatering was required, which was earmarked for disposal in the adjacent Lake Carey Playa system.

MBS Environmental (MBS) were engaged to perform a Tier 1 (high level) ecological risk assessment regarding the planned discharge of water into the Lake Carey Playa. Within this assessment the discharge water was shown to contain elevated concentrations of metals such as copper, cadmium, lead, manganese and zinc. Based on the expected volume of water to be discharged the loading of metals into the Lake Carey sediments was almost certain to exceed ANZECC sediment quality trigger values. MBS were subsequently re-engaged by Dacian to explore whether water treatment options could be utilised to lower metal concentrations prior to discharge. MBS assisted with:

• Assessing the composition of the proposed discharge water against relevant default environmental guideline values (e.g. ANZG Freshwater ecosystem species protection, ANZECC Livestock Drinking Water Quality) to conduct a Tier 1 assessment.
• Calculating potential metal loading concentrations in lake sediments as a consequence of the development of the project and subsequent pit dewatering and discharge.
• Researching possible water treatment processes and options including providing cost estimates.
• Designing and conducting laboratory experiments to test the efficacy of the water treatment options.