Edit: It would kinda be bittersweet for me but I think ultimately I would cry tears of joy which can then be cleansed by Ganges so its cool
Just not polluting it further would do it. It’s a river, so almost everything will get washed away and within a couple decades it will be pretty clean.
Where does all the previous filth and sediment collect?
The stuff that is heavier than water ends up in the river delta, everything else dilutes into the ocean. Once it’s in the ocean, there’s not much humans can do about it. Promoting populations of sea grass and filter feeders like mussels can at least capture pollution in a form that settles to the seabed and improves water quality.
There will be pockets of pollution that persist for a long time, and floodwaters could stir some of that back up, but the above poster is correct. Cleaning up a river can be as simple as stopping the sources of the pollution. A dirty river is dirty because stuff keeps getting added to it. Of course stopping sources of pollution is way easier said than done.
That’s the fun part! It’s no longer your problem. It’s outside the enviroment
But what does that MEAN?!
Its mass is conserved, where does it transition to?
It gets towed (by the river) beyond the environment
Nothing out there but sea, birds, and fish.
And a hundred thousand tons of crude oil.
And a fire.
Most organic things will get converted to biomass/CO2/NH3/… in the end. Inorganics will probably be sediment at some point.
