Ultrafilters, especially steam sanitizable ceramic filters are tremendously effective at removing bacteria. In general a filter with a pore size of 0.2 microns or smaller does an excellent job of removing bacteria. Both of these technologies are used in medicine and industry with great and repeatable success. RO also removes 99.9% of bacteria when operating in spec.
Contrary to popular belief UV does not kill bacteria but instead attacks the mitochondria of bacteria and alters the DNA so the bacteria cannot reproduce. Once treated with UV however, bacteria become fragile and will lyse (break up into smaller particles) and give off pyrogenic endotoxin.
It is important to note that once bacteria are removed from water they will immediately start to grow again because there will no longer be chlorine in the water, and the water will aggressively absorb any contaminants from the air and container.
Distillation will produce a sterile water, but boiling does not remove the bacteria, but only destroy them. Once water is made sterile, that is to say bacteria free, technology must be applied to keep it free of bacteria. That technology can include different combinations of Ultrafiltration, UV, Ozone, sub-micron filtration, constant recirculation of the water, and of course steam.