Aztec Sewage System
The Aztecs had to deal with the excretion produced by 100,000 or more people that lived in Tenochtitlan. This was made possible by creating a sewage system that was quite successful. Faeces was isolated from urine to sit for a couple months. It was then utilised for fertiliser. Urine was filtered through gravel, soil, and the like and then reused. This system utilised the same basic principles that septic tank sewage systems use today.