Reverse osmosis captures water using particles like calcium carbonate, then utilizes activated carbon to eliminate contaminants harmful to reverse osmosis membranes, then uses pressure to push water from one side of the membrane to the other, subsequently removing contaminants in the process, and then finishes it all off with ultraviolet light that sterilizes outliers. This water filtering system filters anything surpassing 5 micrometers ( two ten-thousandths of an inch!).
The ROWPU water filtering system processes upwards of 150,000 gallons of water at a time, or up to 3,000 gallons per hour. It removes salts, chemical agents as well as nuclear, radiological and biological agents. One ROWPU can provide the hydration needs for 6,000 service men and women.
In the Marines, ROWPU is being by the Lightweight Water Purification and the Tactical Water Purification System. The former can be moved using a single vehicle, and the latter can travel on a single large truck. Both process significantly less water than the ROWPU (125 and 1,500 gallons per hour, respectively), but they make up for this reduction with their increased mobility. Different military scenarios will require different water filtering systems at different times.