Pick your favorite large and highly polluted river. You can start with: http://science.sciencemag.org/content/362/6414/503?utm_campaign=toc_sci- mag_2018-11-01&et_rid=40166412&et_cid=2463234 OR https://www.newyorker.com/magazine/2016/07/25/what-it-takes-to-clean-the- ganges Or choose from this list: https://www.conserve-energy-future.com/most-polluted- rivers-world.php And you […]