Water Nazi.

There is a guy at my job who is a complete jerk. I am a pretty easy going person who tends to get along with just about everyone. For whatever reason this guy has decided to not like me. I think it might be the fact that I am the only other male employee in the office and am a good 15 years younger. I don't really care much about what he doesn't or does like. How it came to be I am not sure but he is in charge of our "water club". We pool together and have bottled water delivered to our office. While I was out of work sick due to my car accident my share of the "water pool" went unpaid. This amounts to about $2.00 for the month. Wouldn't you know it that the first day I come back to work the guy sends me multiple emails about my bill even though he sits across the room from me! How ignorant is that?