Potential biogeochemical impacts of heat rejection in the Mullaloo aquifer, Western Australia

• Heated groundwater biogeochemical assessment protocol developed.
• Based on a multidisciplinary study of aquifer/groundwater chemistry and microbiology.
• Regular monitoring required to assess system performance and environmental impact.

A rapid biogeochemical assessment protocol has been developed to assess the potential effects of returning heated groundwater to the Mullaloo aquifer in Perth, Western Australia. A multi-disciplinary study encompassed geochemical analysis of the aquifer sediment, and microbiological, organic contaminant and major ion surveys of the groundwater. Geochemical modelling indicates few, if any adverse implications of a proposed 10 °C temperature increase. A potential exists for chemical and biological clogging but this will be minimised by a closed loop design to avoid the introduction of atmospheric oxygen. Nevertheless, the need for regular monitoring of scheme performance and environmental impacts remains.