Tritium is chemically identical to the non-radioactive isotopes of Hydrogen in water. It does differ slightly in its rate of chemical reactions, rate of diffusion and boiling point (i.e T2O, THO etc. Have slightly higher boiling points) but these differences are small and difficult to leverage at the concentrations involved (parts per trillion and lower) and no matter what process you use, the concentration of Tritium wont be zero. And it doesnt need to be. It just needs to be low enough that the radiation exposure is arbitrarily low enough i.e within normal background level deviation. Which given enough dilution by sea water, it is