I found the same white residue stuff in my water distiller jug too! I figured it was lime or caked up minerals from the hard water. We have well water fed from an underground spring as well. The spring also feeds into a little duck pond in the fields near our home.
I actually enjoy the taste of the distilled water over the plain well water. It seems to taste much "lighter" like the "champaign" version of water!
Tastes even better when you squeeze lemon wedges into it.
Since im very toxic yet from all my years of poor eating, I still need plain H202 to clean me out. But I also appreciate a daily cup of fresh squeezed juice or watermelon :-D