Judging by the extreme reaction with bleach, I am guessing it is something biological. I think a professional water test would be a good idea. I know that Texas A&M has a great water testing facility if you aren't opposed to shipping it to them. Here is the website to get the form with everything you need: http://soiltesting.tamu.edu/files/waterweb1.pdf

I hope this helps

Water dries, rocks crumble, and trees die. The only thing that is eternal is the reputation we leave behind.
- Ancient Viking Proverb