Harmful non-indigenous microorganism invasion caused by ballast water discharge poses severe threats to marine environments. In this study, a conceptual in situ photo-Fenton system without additional oxidants was first established for ballast water sterilization. Pyromellitic acid diimine (PDI)-modified g-C3N4 was utilized as a photocatalyst to produce H2O2, which was in situ activated by Fe­(II) to produce •OH for deep oxidation. Marine bacterium Vibrio alginolyticus (7 log) in ballast seawater was totally inactivated within 35 min of visible light irradiation. Simultaneous bacterial inactivation and H2O2 production was monitored to confirm the in situ coupling mechanism, and •OH instead of H2O2 was determined to be the dominant reactive species. The influence of seawater parameters, such as salinity, pH, and dissolved oxygen, on the inactivation efficiency was revealed. In addition, the bacterial inactivation mechanisms in terms of cell membrane rupture, intracellular enzyme activity, and total protein change were clarified. The organic matter release profile during bacterial lysis was probed by fluorescence excitation–emission matrix technology, which revealed minimal acute toxicity and impacts on the marine environment. This work not only advances an external oxidant-free system for on-board ballast water sterilization using sustainable solar energy but also creates an avenue for exploring bacterial inactivation mechanisms in seawater.

Sustainable and "green" technologies for hydrogen peroxide (H2O2) production have aroused increasing interests, yet challenges prevail in production of H2O2 for environmental applications. In this study, tungsten selenide (WSe2) with...

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