"A mysterious contrivance consisting of a vault hermetically closed by a hydraulic seal..."
Jean-Louis Mouras
The treatment of human waste has varied throughout history from simply throwing it out on the street to complex modern sewage systems. Frenchman Jean- Louis Mouras invented a new type of waste system in the late nineteenth century, which is still used today by communities not connected to main sewer lines.
During the 1860s Mouras built a masonry tank attached to his house to collect human waste, which then overflowed into a regular cesspool. After about twelve years the tank was opened and Mouras discovered to his surprise that there were almost no solids in the tank. Mouras, along with scientist and priest Abbe Moigno, patented the tank in 1881.
The working of the septic tank is simple in concept. Waste enters the tank at one end, is allowed to sit for a period, and is then discharged at the other end. The tank operates when full, so that the inlet liquid pushes out the same amount of outlet liquid. The liquid inside the tank consists of a scum layer on top, a sludge layer that settles to the bottom, and a fairly clear liquid layer in the middle. Decomposition happens via bacteria but solids eventually have to be removed. The bacteria in the tank and the retention of solids are both types of treatment of the waste. The partially treated waste is then released into a carefully situated drainfield, so as to not contaminate groundwater.
