Analysis of Environmental Impact Reduction Effect of Improving Magnesium Hydroxide Extraction Process from Seawater Desalination Brine Using life Cycle Assessment Methodology

초록

As the importance of water resource management increases, seawater desalination is emerging as a key technology for supplementing water supplies. However, the concentrated brine produced by seawater desalination plants poses significant environmental risks, including degrading ocean water quality and disrupting marine ecosystems. Under these circumstances, extracting magnesium hydroxide (Mg(OH)2) from concentrated brine has recently gained attention as a promising recycling technology. This study presents a comparative analysis of the life cycle assessment (LCA) related to Mg(OH)2 extraction processes, specifically comparing the use of freshwater versus centrifuge methods. The assessment reveals significant reductions across multiple environmental indicators: Eutrophication potential (EP) showed the most substantial decrease, reduced by 1.24E-01 kg PO43--eq. (▼30.6%). The second most significant reduction was observed in the global warming potential (GWP), which is decreased by 2.31E+02 kg CO2-eq. (▼26.9%). Acidification potential (AP) followed, with an impact reduction of 5.26E-01 kg SO2-eq. (▼20.3%). Other environmental impact categories also saw decreases: abiotic depletion potential (ADP) by 1.23E+00 kg Sb-eq. (▼16.7%), photochemical ozone creation potential (POCP) by 4.29E-02 kg C2H4-eq. (▼8.0%), and ozone depletion potential (ODP) by 4.41E-06 kg CFC-11-eq. (▼5.5%). In addition, after normalization and weighting for relative comparison of the six impact categories, the improved process demonstrates an environmental impact reduction effect of approximately 26.8% compared to the general process. The study quantified and visualized the environmental impacts associated with NaOH and utility use (electricity and water) in the Mg(OH)2 extraction process, highlighting the components that can be reduced to mitigate these impacts. The results suggest that using alternative hydroxides with lower environmental footprints or adopting more energy-and resource-efficient sediment separation technologies could enhance the environmental sustainability of Mg(OH)2 extraction. Consequently, the findings of this research are expected to provide valuable insights for management and policy-making in the seawater desalination and by-product recycling industries. © 2024, Korea Society of Waste Management. All rights reserved.

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