Ballast waters treatment using UV/Ag–TiO2 + O3 advanced oxidation process with Escherichia coli and Vibrio alginolyticus as indicator microorganisms

Ballast water transfers aquatic species among ports and poses biological threat to the world's oceans. This work investigated the use of combined ultraviolet (UV)/Ag–TiO2 + ozone (O3) processes for ballast water treatment using Escherichia coli and Vibrio alginolyticus as indicator microorganisms. In all tests, the V. alginolyticus cells are more resistant to UV/O3 inactivation than are the E. coli cells. Bacterial cells under stressing stimulated activities of antioxidants for their protection. The combined UV + O3 and UV/Ag–TiO2 + O3 tests yield synergistic removal of both strains compared with individual tests. The combined UV/Ag–TiO2 + O3 process is potentially applicable for onboard treatments for ballast waters.

► We investigated the use of combined ultraviolet (UV)/Ag–TiO2 + ozone (O3) processes for ballast water treatment using Escherichia coli and Vibrio alginolyticus as indicators.
► The combined UV + O3 and UV/Ag–TiO2 + O3 tests yield synergistic removal of both strains compared with individual tests.
► V. alginolyticus cells are more resistant to UV/O3 inactivation than are the E. coli cells.
► Direct damage by oxidation or irradiation rather than action of yielded total residual oxidants in activated cells in ballast waters.