
About 150 years ago the river Medlock in Manchester was considered a fire hazard and the Thames was pretty much guaranteed to kill anyone unlucky enough to fall in.
Both of them cleaned up reasonably well once people started making an effort.
( , Thu 21 May 2015, 9:04, Reply)

It would be inky black one day and bright orange the next, These days it is much improved but is still contaminated with the remnants of heavy metals (particularly mercury) that were pumped into it over several generations.
( , Thu 21 May 2015, 14:05, Reply)

I'm yet to see a river on fire in the UK
( , Thu 21 May 2015, 9:54, Reply)