Identifying environmental remediation and discharge options for Cement Australia

Cement Australia operates a limestone clay mine located in the Mount Larcom township of East End. In October 2022, CQUniversity were commissioned to provide technical assistance with a preliminary investigation of two environmental challenges identified with the mine operations at Cement Australia’s East End site: Groundwater aquifer recharge and management of electrical conductivity levels within surface water discharges. The CQUniversity team (Team) examined the scientific literature and identified challenges similar to those identified by Cement Australia. Identifying possible solutions to addressing these challenges consituted the second aspect of our remit. For each challenge, a list of potential solutions have been identified and presented in this report for consideration by Cement Australia. The first of two systematic literature reviews focused on the management of salinity in discharge water. Published papers relating to currently available technologies for reducing the electrical conductivity (EC) or salinity of produced water were reviewed to identify technologies suited to management of brackish water for discharge to local surface waters. The second topic was based around aquifer recharge and the literature review strategy focused on identifying general, technical information regarding managed aquifer recharge and its implementation, to provide insight and highlight issues for more detailed consideration. For salinity management on site, several technologies based on thermal, membrane technologies, and biological processes can be used as stand-alone or as integrated or hybrid approaches. The report lists nine options for Cement Australia based on these methods. Aquifer recharge is similarly based on various technologies, both in Australia and globally. In Australia however, recharge management in setups where limited recovery for reuse exists or knowledge of environmental impacts and implications for other water users has been somewhat unclear. As well, there is also limited site specific literature available on the use of managed aquifer recharge in mining. However, despite these limitations, the versatility of managed aquifer recharge allowing it to be implemented in a range of geological settings: in soft and hard rock aquifers, porous fractured media, confined and unconfined conditions makes it an attractive option for Cement Australia. The report lists nine case studies using five injection and infiltration managed aquifer recharge types for Cement Australia’s consideration. The report also highlights that the suitability of any system to a site depends on local hydrology and hydrogeology, the type of aquifer targeted, the topography, land availability, water quality and purpose for recharge. In addition, the report expands on the key considerations that should be paramount when identifying the appropriate managed aquifer recharge solution for a site. The availability of Cement Australia’s site monitoring data spanning up to 20 years is an extremely powerful tool to help shape tailored solution to each challenge. Several contingent factors, including but not limited to chemical and physical characteristics at each site, would exert important controls on the success of these methods. To understand how these controls drive the chemical fluxes on site, a detailed data investigation would be beneficial. Following this, it would be possible to select a short-list of options for field trials.