Utilization of calcium-rich groundwater desalination concentrate in aquaculture

Global production of desalinated water increased greatly over the past three decades. Brackish water desalination is energetically favorable compared with seawater desalination, but high treatment costs and negative environmental impact of the concentrate byproduct hinders its development in semi-arid regions. The present study assessed key considerations associated with potential commercial aquaculture in high-flowrate calcium-rich groundwater desalination concentrate. European seabass (Dicentrarchus labrax) fingerlings, weighing 20-40 g were cultivated in brackish water (control), raw concentrate, and partially softened concentrate under flow-through conditions. Aside from two disease-related mortality events, fish survival exceeded 92% during 70 days of cultivation in all water types. The highest average growth rate of 0.26 g d^-1 was obtained in the partially softened concentrate, which was 27% and 83% higher than in the raw concentrate and in the control, respectively. Substantial mineral precipitation on equipment and minor gill damage were observed in fish tanks receiving raw concentrate, projecting serious operational issues under commercial application. Preliminary aeration-softening of the concentrate relieved CO₂ supersaturation and prevented precipitation issues. Several implementation options in a case study fish farm predict commercial and environmental feasibility in specific locations.