Inactivation of Amphidinium sp. in ballast waters using UV/Ag-TiO2 + O3 advanced oxidation treatment

Ballast water poses a biological threat to the world’s waterways by transferring aquatic species from one body of water to another. This study investigates the use of combined ultraviolet (UV)/Ag-TiO2 + ozone (O3) processes for treating ballast water using Amphidinium sp. as an indicator microorganism. Sufficient Amphidinium sp. cells in ballast waters can be inactivated using O3 alone, UV irradiation alone (with or without an Ag-TiO2 coating), and combined treatments. For the low inactivation ratio (<40%) regime, the effects of ozonation and photocatalysis were observed to be cumulative. The combined UV/Ag-TiO2 + O3 treatment produced excess hydroxyl radicals and total residual oxidants (TROs), and readily damaged cell membranes to release intracellular substances. The comparison tests revealed that the combined treatments synergistically inactivate Escherichia coli in ballast waters. However, the combined process did not synergistically inactivate Amphidinium sp. cells. Inactivating different aqua species in ballast waters needs distinct treatment methods and dosages.