As much as I hate it, the real way to achieve the level of compliance you describe is through surveillance, akin to what China does or what Black Mirror depicts.
Changing culture is hard. But, some cultural shifts have been brought about by public awareness campaigns, protests, etc.
How about some education and trusting people to act as grown-ups?
(Disclaimer - I live in Sweden)
Make them realize they live in a beautiful city and that they are a part of it.
May take some time, maybe even decades of barely measurable results. But i believe it is the only method that works in the long run.
Another model is thinking of people as a part of a herd. If noone around you dumps garbage in the river, you are less likely to do it yourself.
You just need to create that positive spiral.
I heard several years ago the picture was similar to neighboring countries (not good). This indicates that the cleanup is possible without introducing total surveillance.
Some level of perceived enforcement is required, but in reality it just needs to be a sign with a high fine on it. And finally some level of public funded cleanup groups and you can get pretty far with keeping spaces clean.