Do you need a completely self contained system, or can you do components? How pure does the water need to be? Do you need completely pure water, or is a 95% reduction in solids acceptable?
R/O doesn't require power, just the pumps needed to push through the 1800 gallons you need to get 600 gallons/day (1200 gallons waste).
Thanks for your reply! Drinking water is not necessary, but if the costs for an RO system that is able to produce such isn't too high, then this is an option too. Writing a private message to you.