Getting stuck without clean water is not a lot of fun. The good news is you can use UV light to purify water in seconds. Take the SteriPen Aqua UV Water Purifier for instance: it can kill 99.9% of bacteria and viruses in your water in under a minute. It is powered by AA batteries to deliver 150 one-liter treatments.
The lamp’s lifespan is about 3000 treatments, so you can make 3000 liters of purified water with this.