I think as others have pointed out the making drinking water safe is a moot point. We know that the making of beer in centuries past killed the bacteria. Making beer to kill bacteria is not needed. Storing water? Its easy enough to boil up some water to make it safe. Sanitation is always going to be interesting after all for all those bottles.
What about bottle caps? You could make some form of cork I suppose but then we are back to sanitation right? And sealing the bottles?
Yeast is going to be interesting too. Most of us may have yeast banks that are held up by refrigeration. Yes, I'm well aware of wild yeast fermentation but the controlling of that starts to get stretched.
The grain may be the biggest issue however. Its one thing to have access to amber waves of grain and all that but to actually process it? Some of us can malt the stuff but I suspect that if that was feasible we would return to the 1500s to the 1800s for malt issues, IE lots of brown malt.
This does not even go in to the growing of the malt, and getting it to the point of harvesting it.
It is an interesting topic but I think that you would see more mead, spirits or wines being produced with out the easy access to grains that we all enjoy today if we have a SHTF scenario of a zombie type of apocalypse. A less than total civilization collapse then grain becomes more available.
Question is for those of you that are confident in producing your own product, do you know how to grow barley, oats, wheat, and rice?
And do you know how much of that it will take to feed a single person for a year? How much to plant to make up for crop losses?
Not cutting at anyone but there is a lot more to this than most think.