In the film Dream Big, we see ways that engineers help build the world of tomorrow. As seen in the film, the population of Earth continues to grow exponentially and to concentrate in major cities. It is estimated that by the end of the century, 90% of Earth’s population will live in a city. With the dense concentration of human inhabitants, we face new challenges to use our limited resources in the most effective ways. Engineers are working on maintaining the health of the water systems in major cities. With more people, we have more waste. How can we keep our fresh water clean?