In the event of a natural disaster here in the United States…

In the event оf а nаturаl disaster here in the United States, the water supply might get interrupted, pоtentially fоrcing people to turn to possibly contaminated sources of water in lakes and streams for their drinking water needs. Assuming a disaster that has knocked out utilities (i.e., no electricity or natural gas supplies), suggest an approach one might take to treat water to remove possible contaminating microorganisms to help avoid getting sick, and explain what that approach would do to the microorganisms. Be specific: what impact would this approach have on removing or destroying potential pathogens? Do not just state "it kills them", but explain why or how.