Thomas spoke about these in his article on purifying contaminated water. Basically, the reverse osmosis water purification systems, like the one featured as #5, will take care of larger contaminents. Couple that with ultraviolet disinfection and the rest of water purification is pretty well taken care of without requiring anything too expensive. Remember that this system requires electrical power, so you’re going to need to take that into consideration. But with a solar panel generator, it’ll do the trick perfectly.