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.
A couple of weeks ago, on a leisurely Sunday afternoon, 40 people gathered at a church in Washington Heights for a show-and-tell session sponsored by the New York City Preppers Network. One by one, they stood in front of the room and exhibited their “bug-out bags,” meticulously packed receptacles filled with equipment meant to see them through the collapse of civilization.
He points to the cash registers over his left shoulder. “I’ll bet you there’s not one thing you bought today that didn’t use electricity in the transaction,” he says. Before Y2K, Finelli says he owned a small computer manufacturing company and personally upgraded 8,000 operating systems so the dates would roll over from 1999 to 2000. “Because they wouldn’t,” he says. “There was a defect. I know that computer systems are frail because I built them.” He says a widespread power outage would cripple us—no electricity, no trading debt portfolios, no buying wholesale taquitos on credit. 
“I was a computer jockey,” he says. “So for example, when you think of press 1, press 2, press 3 on the phone: I built one of the first systems in banking on the East Coast, and I apologize for that.” Finelli’s company began securitizing debt portfolios, a process that began in the ’80s and fed into the mid-2000s financial crisis. Finelli didn’t like that. “That’s when I had that moment of, ‘This is a house of cards,’” he says. So in the late 1980s, he quit and became a farmer, first out East, then in Grovespring by 2005. 
Since people began building fallout shelters during the Cold War, canned nonperishable food has been recognized as great to have around when the going gets tough. Freeze-dried food and MRE (Meal, Ready-to-Eat) military rations with years of shelf life are also good options that take up less space per available calorie. [Doomsday Facts (and Fictions)]

For the Soon to Be Ready for Anything Prepper

The Ultimate List of the 8 Most Important Surviving Skills that will Make the Difference between Life and Death during a Crisis