The technology already exist...
https://www.youtube.com/watch?v=pXDx6DjNLDU
But as the video points out, it is not just cleaning the river but providing a means to keep the trash out of the river. That will take more than just money, it will take the will of the people to do their part.
“That will take more than just money, it will take the will of the people to do their part.”
Major cultural change. But that’s how societies evolve.