The watercone is great for non-potable water that isn't contaminated with compounds that also boil below or near 100 °C and are either in A) high proportion or B) that bio-accumulate.

If the preliminary findings with the graphene oxide are hold true, you could stick a cap made of the stuff on a watercone evaporating a bunch of zombie blood and end up with ASTM Type I water to keep you hydrated after the zombie apocalypse.

In order for this statement to be relevant I think you must be of the opinion that zombie blood contains compounds that boil below or near 100°C. Otherwise you still wouldn't need graphene oxide cap.

So I'm wondering if zombie blood is known to have these type of compounds. But more importantly, how common is it for typically impotable water to have these type of compounds?

Ignoring the zombie blood for a second (because you're absolutely correct) I'll approach your last question.

> how common is it for typically impotable water to have these type of compounds?

My gut feeling is, "not very... right now." The "right now" is pretty much the problem with the speculated water wars (though a bunch of the water in the Gulf of Mexico does contain those compounds).

With landfill's "impermeable" barriers becoming permeated and cholesterol medications, caffeine, birth control, and various other drugs remaining in the treated effluent from waste water facilities coupled with humanity's generally reckless disregard for consequences to its actions there's a significantly non-zero chance that fresh, clean potable water will become scarce in multiple developed locations worldwide.

On the other hand, it could very well be that as our understanding of bio-remediation increases and our utilization of passive and active purification techniques and/or technologies increases we'll keep from having that be a problem. Potentially, we'll even stop actively polluting our water supplies with industrial, agricultural and residential wastes to "save a buck."

Anyway, the watercone is great. They've tackled usability issues present in other solar distillation devices and for areas with access to water with high salinity, or biologically contaminated water (though, there is risk of cross-contamination when harvesting your purified water). It's just that solar stills aren't always a replacement for filters.

Off the top of my head, I can think of one toxic substance that easily mixes with water and boils below 100°C: methanol.

Some hydrocarbons might also fit the description.

You're right, which would explain why they experimented with vodka. It seems this filter is better at filtering water out of a substance, rather then filtering substances out of water.