I meant on Earth. But, the Imperial City is the only city in the game that appears to have a functioning sewer system. Have you read the Guide to Bravil? Doesn't sound like there are any sewers there.
edit - Here is a direct quote from the book: "Beggars and thieves lounge indolently on balconies overhanging the streets and dump their refuse directly upon the unfortunate passers-by ... " I don't think she's talking about emptying the kitchen garbage.
edit 2 - and another quote: "The climate is damp and the atmosphere foul because of the fetid channels of the Larsius River that serve as Bravil's sewers." So I don't think Bravil has anything resembling the sewers of the I.C.
You're right in the dumping part, but sewers have been around at least since the Roman empire...
York, London, Paris, Rome all have sewers dating long beyond any TES relevent timeline, they still dumped waste but expected it to wash down.
On a relevant note motor vehicles were considered an ecologically friendly alternative to horses, due to not having fecal waste spread all over.
Horse [censored] however was a prime source of fuel for houses, for cleaning hides for leather ( though dog [censored], and chicken crap was better ), and also used as fertiliser with human waste as well.
Many lower class people kept themselves fed by scauaging this and other foul detritus, even quite recently so, post war sometimes.
Edit: Tanners however were well paid, but had to live and work on the outskirts due to the aroma they carried with them.
And had some pretty nice / nasty tan lines up their arms.