Electricity interrupts nerve impulses, which isn't helpful for microorganisms without nerves. It could help with nematodes and some some other animal pathogens. But water isn't a very good conductor of electricity and it would be hard to ensure that it's effective at killing everything rather than just some/most things.

Another way electricity kills stuff is by heating up the organism enough to cause severe tissue damage, but this is difficult to do with water and will take a lot of energy. Boiling has the same effect.