Process for disinfecting seawater

The invention provides a process for disinfecting seawater, the process comprises the steps: (i) contacting the seawater with pure oxygen 20 so as to produce purified seawater 30; and (ii) electrolysing 3 the purified seawater to produce hydrogen 40 and oxygen; wherein the oxygen produced in step (ii) is at least partially recycled for use in step (i). The pure oxygen may be provided as a gas stream consisting of pure oxygen and ozone. A portion of the oxygen produced in step (ii) can be used to produce ozone. The power required for step (ii) may be generated by one or more offshore wind turbines. Suitably, the purified seawater produced in step (i) undergoes desalination prior to step (ii). Apparatus for performing the method comprises: a contactor configured to contact seawater and pure oxygen to produce purified seawater which exits the contactor via a liquid phase conduit; and an electrolyser receiving the purified seawater to produce hydrogen gas which exits the electrolyser via a first outlet and oxygen gas which exits the electrolyser via a second outlet. The second outlet provides oxygen gas to the contactor. The use of pure oxygen for disinfecting seawater is also claimed.