Minimizing marine pollution transfer via ballast water: AOP-based chemical decontamination, efficiency comparison, and LCA study

Ballast water is a relevant vector for the dissemination of chemical and microbiological pollutants, raising concerns about its environmental impact on marine ecosystems; in this context, advanced oxidation processes (AOPs) is a promising alternative despite the high salinity of seawater. This study evaluates the performance of several AOPs (UVC, UVC/H2O2, UVC-driven photo-Fenton, O3, O3/UVC, and VUV irradiation) for the degradation of a representative mixture of six contaminants (phthalic acid, dihydroxybenzophenone, 2,4-dinitrophenol, bisphenol A, pentachlorophenol, and benzylparaben) in real matrices. Highest removal rates were obtained by ozone, reaching 100% of pollutant removal in less than 15 min; additionally, VUV and UVC/photo-Fenton showed good efficiency even in saline waters (80 – 90% removal), although longer irradiation times were required. A comprehensive life cycle assessment (LCA) was performed to compare the environmental sustainability of each treatment, which revealed that energy and reagent consumption were the key parameters. Significantly, VUV showed the lowest environmental impact in the scenario that involves using the excess of energy from the ship engines and N2 reuse (decreasing 2 – 3 orders of magnitude between scenarios, c.a. 6.2·10−6 g CO2 eq). The integration of avoided toxicity analysis further confirmed the environmental benefits of treating ballast water. These findings support the implementation of photochemical AOPs as on-board ballast water treatment strategies, balancing efficacy and environmental sustainability.