この水は殺菌してある。

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

water (esp. cool, fresh water, e.g. drinking water); fluid (esp. in an animal tissue); liquid; flood; floodwaters; water offered to wrestlers just prior to a bout; break granted to wrestlers engaged in a prolonged bout

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

sterilization; sterilisation; disinfection