Short form question:

Should I treat water with chlorine or iodine prior to freezing for long term emergency storage? I've bought gallon bottles of water in PET containers with handles. I was planning on opening the bottles and pouring out a small amount to allow room for freezing, but I'm not sure if I should also chemically treat beforehand for long-term storage.

Long form:
In a step that guarantees I'll be reminded how old I'm getting, as this is the sort of thing my parents used to do, I've just converted an old refrigerator in the garage to a wine cellar. Using a commercial thermostat intended for the purpose, the upper box is now temp controlled at ~55 degrees F. The unit basically cycles the fridge/freezer power on/off to regulate the temperature in the fridge box.

Unfortunately, good wine temps means that the freezer portion usually hovers around 20-24 degrees F. This is cold enough to freeze, but not cold enough that I consider it "safe" for frozen food storage, especially since the temperature cycles up and down as the wine thermostat does its thing. (And its obviously too cold for beer storage!)

I figure I could create a win-win-win situation by using the freezer as additional emergency water storage. Having six or so gallons of frozen water in the freezer box will also add thermal mass and smooth out the thermal cycling as the thermostat does its thing, which is better for the wine, and lastly it means I'll have a bunch of extra ice on hand should I need to transfer that to my real frozen food storage areas in case of extended power loss.

Given that I'm using commercially bottled water, should I even bother? As it happens the water that came in the containers I prefer is that "filtered" product, meaning its basically treated tap water, not spring water. But I will need to OPEN the containers to make room for freezing, thus introducing a possible contamination point.

Also, everything I've read says that halogen treatments such as chlorine and iodine don't work well at low temperatures. I guess I would treat at room temperature for the recommended time, then freeze, but still not sure if its (A)worth it, and (B)potentially giving me false security.

Opinions?

Thanks much.