Repost from here, thought I've added a few bits here and there based on the conversation in the thread and a few things that came to mind since posting this on FB.
... This is kinda long... Sorry. I have a public service announcement. As some of you may recall I was advocating using some of the Yams for making alcohol even after it was decided that it wasn't the time for intoxicants AND confirmed that they were food. Mostly this is for water purification purposes (among other things). I was a little cagey when pressed for details on how to do this because since moving to Texas (where earthquakes aren't so much an issue) I've kinda slacked on my disaster preparedness and I didn't want to give information that wasn't factual. Because there are other types of disasters that can happen in Texas and this is important stuff to know in general.
The GMs will correct me if I'm wrong about this Mechanics wise, but I would think that anybody with at least a Survival 1 would know this (other skills may be applicable as well, but that's not up to me.) Water must be purified after it is filtered. This is because your filter is only as good as the smallest holes in it. Limestone will filter a lot (we can also use alternating layers of that, and/or sand, and/or charcoal for even more efficient filtration), but protozoa and other single celled critters can still get through and make people violently ill.
There are a couple of ways to do this that are viable options for the colonists in my personal opinion.
fill clear bottles with the filtered water and leave on a reflective surface (if available) in direct sunlight for... a day or two depending on the amount of sun in a day. The radiant heat and sunlight will kill the microscopic critters. This takes up bottles, space, and takes up quite a bit of time though it's not like the bottles need to be tended.
Boil and/or distill the water after it has been filtered. You can do this with fire for speed or (again) leaving it out in the sun for natural evaporation and condensation to do the distilling for you. Using sunlight, again, takes up TIME. Using heat/fire takes up man hours to tend the fire and gather whatever is being burned AND requires special(ish) equipment, is a bit dangerous, and takes up resources like the fuel for the fire. However, we'll be burning stuff for light and warmth anyway, so it's a possible two-birds-one-stone situation. Also, burning plant matter will result in charcoal and ash both of which are useful (The charcoal can be cycled into the water filter and the ash can be used to make lye.)
Iodine, Hydrogen Peroxide, Bleach, Chlorine, and liquid oxygen can be used in small amounts to purify large quantities of water. Resources of those are probably low or non-existent. (And space-faring grade LOX, if we have any in the drop pod's systems, is VERY dangerous stuff.)
Using electricity to make Ozone which we pump through the water will also kill the bugs.
One part modern commercially produced wine to three parts water will kill the "bugs" (the average assumed alcohol content of wine is something like 12.5%-14.5% I think?). The historic recipe for Grog is 4 parts water to 1 part rum. (Which is way more rum than you need to purify water but they were drinking stagnant unfiltered water and the drink was supposed to be at least a little intoxicating because it was a reward.) Hard spirits requires distillation so there's that man hours/special equipment/resources. Beer also works.
So to make a long story short (too late), the ratio depends on the alcohol content of the thing you're mixing in to kill off the "bugs".
And finally (It's over soon, I promise), to counter the argument that it's better to use the yams as food rather than making Yam Beer out of it I will say that I actually agree. However, brewing at least some of the Yams into beer, or doing so with Yams that are in danger of going off, is a viable way of preserving those precious calories. The alcohol is a preservative, and the beer could be used to cook fresh yams. Thus bringing out alcohol soluble flavors and making it more tasty, adding calories, and the alcohol will be cooked off negating the dangers of being intoxicated when the Clickers come around to kill us.
I hope that was at least mildly interesting to those of you who stuck with me until the end.