In place where the treatment plants are not available or can not be immediately constructed for economic and other reason and any of the following miscellaneous method can be adopted.
Septic tank:
The septic tank is widely used in semi urban areas like small group of house, institutional,hostels and isolated building where water carriages system and treatment plant is not available for feasible.Thus this system can be considered as a compromise between full pledged water carriages system and conservancy system.
The septic tank system combines four operations namely
a.Sedimentation of settleable solids.
b.Anaerobic digestion of settleable sludge.
c.Stroage of digested sludge for a long period about 1 to 5 years depending on the design and
d.Soakage of liquid effluent from septic tank into the ground through soakage pits in which partial oxidation of dissolved and collidial organic matter is done in areobically.
Construction and operation
Septic tank is a single chambered masonry or concrete rectangular tank with a water tight concrete floor at bottom.The inside of the tank is provided with a water tight plastering preferably mixed with water proofing material.It consists of an inlet pipe and outlet pipe of tee section or ordinary pipe with inlet out let baffles so as to avoid scum to enter into the pipes.The top of the tank is closed with R.C.C. slab and is provided with the man hole.It is also provided with a vent pipe for a sufficient height to allow the garden produced in the tank to escape in to the atmosphere.The minimum width of the tank is 1.0m so as to aollow man to enter for cleaning.
The sewage from the urinals and water closely in allowed anaerobic conditions in about 30 to 50 days depending on availabile temperature and other conditions.This digested sludge is stored at the bottom of the tank upto the end of Cleaning period and then removed through man hole.This cleaning operation is very important for the efficient functioning of septic tank.Otherwise the tank will be completely filled with the sludge and there will be no space for sedimentation.
The septic tank is so designed that there is sufficient space for sedimentation digestion and storage during the complete operating period.The effluent of the septic tank contains about 60 to 70% of B.O.D and hence should be treated and then disposed.
Soak pit:
It is a circular or square pit of sufficient dimensions minimum dia is 1m and depth 1.5m.The pit is fitted with brick bats or coarse aggregate.The effluent is applied into the pit so that the areobic bacteria film on the surface of brick bats oxidation the dissolved organic matter.The waste water then percolate into the ground and thus finally disposed.The size of the pit depends on the quantity of effluent to be precolates and then permeability of the sub soil.