Historical cities were hideous, open sewers, their streets clogged with human and animal filth.
. . . or were they?
Two groups of people would have you believe that’s true: writers of a certain type of gritty fantasy, and the Victorians. And certainly there have been times and places when it’s at least partly accurate; I can’t swear that Renaissance Europe was the filthiest society this planet has ever seen, but I suspect it’s a serious contender. If you look at other time periods and other parts of the world, though, a different picture emerges. Even before germ theory, we didn’t much enjoy wading through rivers of fecal matter, and took steps to deal with waste.
I said last week that humans like to settle along rivers because the flowing water will carry their waste away. When the settlements remain small, this works decently well: the ratio of waste to water is low enough that you don’t wind up with significant problems (though it’s still true that the farther downstream you are, the more problems you have). But when you get up to the level of a large city? Then, my friends, you wind up with something like the Great Stink.
Such things aren’t inevitable, though. These days we have treatment plants to purify wastewater, separating the solids out (and sometimes disposing of them by methods like incineration) and cleaning the water so it can be used for other purposes — a big improvement on dumping it all in the ocean, where it kills wildlife. But even in the past, we often had better answers than merely throwing it in the river, much less the street.
Cesspits get a bad name, with the term literally being used as an insult for undesirable locations. And when they’re simply holes in the ground, that’s fair, because then the liquid component soaks into the earth and will eventually contaminate your groundwater. But if properly constructed, a cesspit is watertight, and can store sewage until the chamber is emptied — much like a modern septic tank. The euphemistic term “night soil” for human waste comes from the fact that the emptying was usually done at night, when it would be less unpleasant for the neighbors.
Mind you, that isn’t to say that cesspits were without problems. They didn’t get emptied nightly; in fact, years often went by between visits from the night soil men. In the meanwhile, the contents fermented into an amazing stew of infection and dangerous gases, which could asphyxiate the workers or even explode. But still: compared with just chucking the contents of your chamber pot out the window, or piping sewers directly into the river, it isn’t a bad system.
Especially when you consider that sewage can actually be valuable. Solid waste is useful as fertilizer; so is urine, which is rich in nitrogen. The latter is also handy as a cleaning agent (even for teeth, ick), as a fixative for dyes and a fulling agent for cloth, and for the production of potassium nitrate, used in making gunpowder. In fact, there’s at least one time and place in history when human waste was so valuable, people actually stole it.
That time and place was Tokugawa-era Japan. After the shoguns closed the country to almost all foreign trade in the early seventeenth century, the country became a self-contained system, and had to support itself on local materials. (You actually see the effects of this all over traditional Japanese culture: everything from the cuisine to the architecture now bears the stamp of making efficient use of limited resources.) Because Japan is so mountainous, the small amount of arable land had to be devoted much more to crops than to livestock, since the former produces many more calories per acre than the latter. Which mean you simultaneously needed a lot of fertilizer, and had fewer animals to collect it from.
The result was that human waste was a vital agricultural resource. Of course we have to be more careful using it than we do with animal manure — there’s much more risk of contaminating our food with undesirable parasites and such — but as long as you take precautions, you can make it work. For a while there, barges would come into cities like Edo and Osaka laden with crates of produce, and would go out again laden with barrels of waste. When this system started to fall apart, it was because the waste had actually become more valuable per unit of volume than the food. Business owners would hold licenses to maintain public lavatories and sell what they collected there — which eventually led to complaints to the magistrates that someone had stolen their property. Tokugawa Japan had some of the cleanest cities in the world, because shit was too important to let it just lie around in the streets.
Even without those specialized conditions, it’s entirely possible to have moderately clean cities without modern technology. The real determining factor is public and governmental will: do people care enough to put the money and effort into dealing with their sewage? You need a strong local authority to enforce laws about where you can put your waste, and investment in the infrastructure necessary to make it work. You need well-organized systems of removal, and sensible precautions in how you go about doing that.
So when we’ve backslid from good arrangements to bad ones, it’s generally because of some kind of social breakdown. This might be a disaster along the lines of a civil war or a plague, but it might also be something like a trend of corruption in government or economic stratification that means the elite look out for themselves while leaving the poor to fester in their own sludge. Or it can even be an unfortunate by-product of success: the Great Stink happened in 1858 not because Victorian society was falling apart, but because the massive growth of London had outstripped the ability of the city’s infrastructure to deal with the consequences. You see similar problems in other boom locations today, like India’s rapidly-growing cities.
Whether a fictional society is going to have clean streets or open sewers therefore depends less on technology and more on what kind of socio-economic conditions the writer sets up. If the local government is generally efficient and fair, things won’t be too bad. But the more things slide toward top-level callousness, ineffectiveness, or absence, the less pleasant a stroll through town is going to be.