[OJFord]

> Apparently some emperor did realize that it wasn't smart to bathe with sick and healthy people at the same time but decided the sick would bathe before the healthy

Maybe he thought they were more in need of cleansing.

Even with today's knowledge, without application of today's tech (overnight chlorination say) it wouldn't really make a difference? Today's first bathing session comes after yesterday's second.

[thatcat]

A simple bioactive sand filter would probably be sufficient https://en.wikipedia.org/wiki/Biosand_filter

[OJFord]

That too came a bit late:

> proposed by Dr. David Manz in the late 1980s [...]