Whoa... You work in the lab and you seriously ask this kind of questions?... *facepalm*
Not sure what you mean here... because there is no microiological reason to prefer dH20 in stead of using tap water...
Same goes for ddH20.
I do not know from what lab you are, but in my lab MiliQ water doesn't contain bacteria. At least not at the point leaving the machine.
You are using MQ water to make 70% ethanol? Either you are not cleaning a lot with that or your lab must be filthy rich..
I also wonder: how often is your MQ system checked? Because often labs buy this kind of equipment, but dont really check it like they should.