Outhouse - Biological Processes

Biological Processes

An outhouse is primarily a hole dug into the ground, into which biological waste solids and liquids are introduced, similar to a cesspit. If sufficient moisture is available, natural bacteria within the waste materials begin the fermentation. Earthworms, amoebas, molds, and other organisms in the surrounding ground soils and flying insects entering the privy hole also consume nutrients in the waste material, slowly decomposing the wastes and forming a compost pile in the base of the pit. Bacteria form a complex biofilm on the wastes and in the surrounding exposed soils around the perimeter of the pit and feed on the wastes splashed or dropped into the pit.

An outhouse operates differently from a septic tank in that the pit is not normally filled with standing water. The solids act as a sponge to retain moisture but also are exposed to open air, allowing for insects and earthworms to feed on the wastes which would not be possible within a septic tank. Septic tanks also tend to contain only organisms that can survive anaerobic conditions, while the open outhouse pit can sustain both aerobic and anaerobic organisms.

The process of decomposition is slow due to the layering of waste materials but is generally effective if the input of new wastes does not exceed the decomposition rate of the bacteria and other organisms. Small amounts of moisture from urination are absorbed by existing decomposed wastes in the base of the pit. In soils where the percolation rate of water through the soil is slow and where there is not a large amount of waste entering the pit, the wastes can slowly decompose and be rendered harmless without causing groundwater contamination.