""Hard to imagine a modern factory manager "cheerfully" agreeing to comply with the construction of a "huge purification plant" to put an end to pollution. Seems like polluting has gone from being something to be ashamed of to something that's accepted as the price of progress.""
I guess that's one (cynical) way to look at it. Another perspective might be that now, companies and individuals are much more aware of the harm that dumping chemicals can cause to the environment, and would not intentionally release it into a river. We live in a time where it is trendy to blame big companies for everything bad, but I believe many, maybe most, try to be compliant for reasons of stewardship and/or penalties. That is why it wouldn't intentionally happen now.