We, the human race, have had sewer systems for a long time. Depending on how you define a sanitary sewer system, we have been making efforts in that direction for perhaps six-thousand years, or even more. We have been needing them even longer, of course, but what could we do? As long as we were wandering around hunting and gathering, it was not much of a problem, as we would be somewhere else before the waste left by our little band became a serious problem. But when we started to stay in one place, forming communities and even cities, something had to be done.
Archaeological excavations of some of the ancient civilizations of the Indus Valley have revealed that sanitary sewers were in place and quite sophisticated, considering the materials and tools at hand. Those early civilizers often had a sort of septic tank under the house, with broken pottery used to form a drain field of sorts. The toilet not being invented yet, access to the system was by way of a hole in the floor. But that is progress, at least.
Those old castles that you might visit if you make a vacation trip to the isles of the United Kingdom often had sanitary sewer systems of one sort or another. Those go back a few thousand years as well. They may have even taken care to keep the castle sewage out of the moat, so that the water could be kept clean and fishes caught to be served on Fridays. Those old castles also had some of the earliest attempts at what we might call a water closet, though mostly without the water. To be exact, it would have been a sort of alcove into the wall, with a hole leading to the under-the-castle sanitary sewage arrangements. That would be an improvement on a bucket beside the bed in milady's chamber, I'm sure we can agree.
A lot of other civilizations that may not get the press they deserve had good early sewer handling systems, like the Chinese and the Egyptians. Some of the societies and cities that we might tend to think of when considering older yet civilized societies considered the streets to be the sewer system, at least until they learned better. Rome eventually did develop a sewer system, with some interesting public toilet arrangements. They were of the mind, as we have been until only recently, that flushing the residue into the Tiber was an acceptable means of dealing with it.
In Europe and the US, the need to develop sanitary sewer systems arose as cities became larger and populations more dense, especially as a result of the Industrial Revolution. In the US, it has been standard practice to have good sanitary sewers in our cities since about the middle of the twentieth century, perhaps a little earlier. It seems hard to believe, but it is true, that is has not been all that long since the bathroom was out back in a little shack of its own.
Now of course, we have sanitary sewers by agreement and decree as well. In large cities we have large sewer systems, that have grown vast enough to even accommodate the urban legend of giant alligators in the sewers under New York City, ever ready to dine on the unwary city worker or other unfortunate. In your town you have an excellent sanitary sewer system, which hopefully leads to an advanced treatment facility, and not to the river. To connect you to that sewer in your hour of need you have plumbing. And to keep that plumbing flushing and flowing we have plumbers. So there it is: From a short walk in the woods to a low-flush toilet; from the gutter to a computer-monitored sanitary sewer system; we have come a long ways.
Let us hope that the future of the sanitary sewer system leads to more concern for the environment and the planet, without sacrificing comfort and convenience. We don't want to go back to using the streets as sewer systems; but let's keep our waste out of the Tiber as well.