Direct Current (DC) is used by electrolysis. Some people use electrolysis to structure their water, although it seems to only be a temporary solution in terms of structured water. In Japanese science, Pangman and Evans found that “…the quality of alkaline ionized water deteriorates rapidly, regardless of preservation conditions.”
Machines that ionize water separate the positive (alkaline) from the negative (acidic) charge so that only the alkaline water is consumed. Although it seems to go against the pattern of nature, some people have enjoyed using water ionizers. Science is continually changing as more research is done, and it is not yet known how exclusive consumption of alkaline ionized water would affect humans.
In their research, Pangman and Evans found that structured water that is polarized, containing a balance of both positive and negative charges, is very beneficial. However, it is important to the individual to do what works best for themselves since everyone is different.
Reference: “Dancing With Water: The New Science of Water” by MJ Pangman, MS & Melanie Evans