Clogging mechanisms in managed aquifer recharge: a case study at Mining Area C

Managed Aquifer Recharge or MAR is a well-established method of sustainable water management. The changing climate, growing population, effects of urbanisation and surface water scarcity increase pressure on future global water resources. While MAR has been primarily utilised for potable and agricultural purposes in the past, it has future potential to form an integral part of water management in the mining industry. It is an effective and sustainable method for disposing of surplus water in an operational mining capacity and can reduce the long term dewatering footprint of below water table deposits. Clogging of the injection well and surrounding aquifer matrix is a common operational issue that results in reduced permeability of injection surfaces. Clogging can occur via physical, chemical or biological mechanisms or a combination thereof. The MAR scheme at BHP Billiton‟s Mining Area C in the central Pilbara was used as a case study to investigate the potential for clogging mechanisms to affect operational performance.
The MAR system at MAC injects surplus dewatering supply from mineralised iron-orebody aquifers into the regional karstic dolomite aquifer. The trial commenced in April 2012 and available data was analysed until April 2013. The regional aquifer showed a maximum 5m increase in groundwater levels in response to the trial. The operational performance of the injection bores decreased throughout the study period and one injection bore was shut down prematurely due to poor performance. The well efficiency significantly decreased in two of the three bores as a result of injection. A comparison of bore casing images pre- and post-injection showed a significant increase in the clogging layer area. Test pumping had a minor remediation effect, reducing the clogging layer by 10-15%. As such, clogging mechanisms had a moderate impact of the operation of the MAR system at MAC.