Comparison of the inactivation of Uronema marinum in mariculture by UV/chlorine, UV/monochloramine, and UV/chlorine dioxide: Efficiency, mechanism and feasibility

Abstract

Despite a growing interest in advanced oxidation processes (AOPs) for the inactivation of harmful microorganisms, there is relatively little research on the inactivation of harmful protozoa in aquaculture water. The research investigated the effectiveness and mechanisms of UV/chlorine, UV/monochloramine (UV/NH2Cl) and UV/chlorine dioxide (UV/ClO2) inactivating Uronema marinum (U. marinum), and assessed the feasibility of these processes in marine aquaculture. Three AOPs effectively inactivated U. marinum in the following sequence: UV/chlorine > UV/NH2Cl > UV/ClO2. Furthermore, the concentrations of free radicals (OH, Cl, and ClO) generated in the three AOPs exhibited the same order. In the investigation of the inactivation mechanism of U. marinum, transcriptomic analysis results indicate that the effects of chlorine-based AOPs on the transcription, translation, and lipid metabolism of U. marinum may be critical factors of the inactivation of U. marinum. Additionally, the feasibility of chlorine-based AOPs for inactivating protozoa in marine aquaculture was assessed through pathological analysis of fish. The results indicate that compared to UV/chlorine and UV/NH2Cl treatments, tilapia cultured in seawater treated with UV/ClO2 had lower mortality rates and minimal damage. This study provides valuable fundamental information for the selection and operation of AOPs to deactivate harmful microorganisms in marine aquaculture water.