On-site sanitation systems are widely used in rural areas of both developed and developing countries, and in the absence of more costly sewerage system, is also extensively used in urban areas of developing countries. When the wastes are collected, treated and disposed of at the point of generation, it is called an on-site system like pit latrines and septic tank systems. The simplest on-site sanitation system is a pit latrine, which consists of a manually dug pit covered by a concrete, wooden or bamboo slab with a squatting hole. Some form of superstructure is erected over the pit to ensure privacy to the user.
The on-site sanitation system has, over the years, been developed and improved into a lot of different designs like ventilated improved pit latrine, pour-flush single and double pit latrines, septic tanks etc.The basic on-site systems are primarily designed to dispose of human excreta. Waste waters from cooking, cloths washing and bathing are collected in small drains and disposed of in soakaways for infiltration.
On-site sanitation systems are most suitable for sparsely settled rural areas with low population density and low water consumption because of the system’s dependence on the infiltration capacity of the soil for disposal of the liquid portion of excreta. Infiltrating liquid waste however, is a potential cause of groundwater pollution.
Where on-site sanitation system is not feasible because of high population density, high water consumption, low infiltration rate of soil or high groundwater table, wastes have to be collected and transported off-site for treatment and/or disposal.