The problem with most water purification methods is that they become clogged and need to be replaced over time. A new technology developed by researchers at Princeton University doesn’t require filters at all, instead relying on the injection of CO2 gas to change the water’s chemistry and separate waste particles based on their electrical charge. Simple and low-cost, this technique could be used in a portable water purification system, or it could be scaled up to help communities produce large quantities of clean water.