Well, I’m not familiar with the specifics on that river, but my general understanding is that these sort of things (pollution) occur when you have “tragedy of the commons” scenario.
If the river is communally “owned” then everybody owns it and nobody owns it. Companies pollute it but no one has a legal basis to do anything about it because they have no legal standing. Local government’s should do something but don’t more often than not due to either incompetence or cronyism (being paid off to look the other way).
If landowners could also own part of the river they would each have an incentive to see that their property is not violated through pollution and would have legal standing to sue any polluter.
Well defined and enforced property rights pretty much solves every single environmental issue. Pollution is only a problem because our current system allows for “public” spaces that have no protection, those public spaces then become public dumping grounds and we then act surprised that some people would shift cost burdens from themselves to society at large (polluters) so the statists see no other solution than to give the government more power to fix the very problem they created in the first place by not enforcing property rights.