Gotta get those scientists learning about microorganisms.

8525868
First, he has to invent microscope just to show those ponies what germs look like.

The Lightning Bringer

Speaking of which:

Hopefully, he knows not to use lead pipes

8525912
that's like, the original "ONE THING" learning moment that kickstarts any child engineer into growing up with "armchair society logistics technician" as their lifelong hobby.

Pretty sure he knows about it!

8525992
I know its just very important to not forget

If you want inspiration, search for the story An American geek in helkagania.
Also https://forums.spacebattles.com/threads/what-can-sb-teach-an-evil-queen-hiatus-would-imply-intent-to-return-which-is-inaccurate.426112/

Not gonna lie I was expecting him to mention the black death. If they ask where he came from he can just say most of his species was wiped out due to the black death and he survived because he was a doctor that discovered being sanitary mostly prevents it. Even though he isn't a doctor he is probably smarter than the current pony doctor's.

The big problem for sanitation in the cities was the population density verses the disposal speed from storage and leakage. That, and equine waste is toally different to human waste due to their far higher carbon content of vegetation food than the nitrogen containing meat based human food. One tourist information centre in Cardiff, Wales I beleive it was, used a simple pile of horse manure to compost down, and below it placed a water loop, that on being heated, flowed up the hill to the radiators in the building. Or underfloor heating depending if you knew about hypocaust and could put the piping down before the mosaics were placed. Then again, hypocaust also went up the hollow walls, improoving thermal insulation even when not active.

Get the stuff out of the city, great long drop sewer pipes, and around the othre side of the mountain, once wind directions have been agreed on, build the evapouration pans and compost heaps. Which is why they were called sewage farms, because the compost was spread on the crops to greatly fertilise them. If thers no enough room locally, thats what the railways are for. Finally, the nobility can actually be useful for fertilising the rest of Equestria, instead of keeping all the cp to themselves.

This is a very refreshing reading, i hope you continue this, it makes my day and now im very calm, the conversation in the bath was soothing, very well done :D.

8525881
Not neceseraly, the first time humans discovered microorganism, it was with lenses, with an spherical shape, so he could instruct in its construction.

8525881
8526665
Besides, they already have telescopes, so they clearly have the ability to make magnifying lenses.

8526675
This is in the past of Equestria, telescopes are not assumed.

Color me intrigued...

Once again I am intrigued by one of your stories. Good show!

8527050

8537394
That's twice in a row with that word. I can think of much worse words, so I accept your intrigue and hope to live up to it.

Celestia seemed to cotton on to the idea of germs quickly enough. I mean, yeah, it was something that took our ancestors a long time to cotton on to, but I think if you had somebody who was from a clearly more scientifically advanced culture, the notion of "You have small creatures that harm you. Now imagine they're smaller to the point you can't see them with the naked eye. The blood in your body can be subdivided into individual tiny fractions. These creatures are as small as individual drops of blood or smaller and can get in and harm you" isn't hard to follow.

Of course, if Luna is banished at this point and this is new stuff Celestia is just learning, boy oh boy won't Luna be in for a cultural shock when she returns.

Visions of a pony dipping their snout, only to wrench it back with an alarmed yelp danced through my mind. "No, that wouldn't be reasonable at all." I worked down to her hind legs and lowest belly. Though concealed by fur, she did have all the parts needed to support a foal, if ever she had one. Had she? I couldn't say with certainty either way. Her inner legs were just as sensitive. She twitched silently as I worked the area. "The first step is making sure filth doesn't get between the source of the water and the endpoint. No matter how clear and lovely a pond or reservoir may be, it can arrive infested and deadly. This comes to an expensive, but required--"

However, it would be much more preferable to use continuous flowing water than stagnate water. Also using basic charcoal, sand, and rock particle filters to removed all debris. Then boil the water to kill bacteria or chemically treat it with iodine tablets.

"Water, my jewels, kindly."
I snickered.

Yes, another great start to another great story.