This is super weird but just a few days ago Mike Patey (guy behind the draco bushplane [1]) posted a video [2] about his next airplane build and briefly showed a huge evap tower that he described as being for separating water produced in the petroleum industry. Oil water separation doesn't exactly sound like a millennium challenge problem so I wonder if there's some sort of grant competition right now.
Oil water separation is actually really hard, it's been a huge problem for over a century. There's a lot of research being done on the topic, dozens of teams from top universities around the world working on it; just look through recent issues of Energy & Fuels, for instance.
Luckily for the environment, it is one of those cases where "more oil emitted into waterways = less money earned", through less amount of product, or less valuable product - cleaning up the oil and cleaning up the water often go hand in hand.
[1] https://news.ycombinator.com/item?id=17743960
[2] https://www.youtube.com/watch?v=G9MNWh8kkIM