After conveying the sewage through sewers, the next step is its disposal. The sewage can be disposed of without treatment or after suitable treatment finally, the sewage is disposed of either in natural water courses or on land.
Methods of sewage disposal can be classifieds under
The natural methods
- By dilution
- Land treatment
The artificial methods
- Primary treatment
- Secondary treatment
The disposal of sewage by discharging it into watercourses such as streams, rivers or large body of water such as a lake, sea is called dilution. This methods of disposal are only possible when the natural water in required quantity is available near the town. While discharging the sewage in this way care should be taken that the sewage may not pollute the natural water and render it unfit for any other purpose such as bathing, drinking, fish culture, rough industrial use and irrigation.
When the sewage is evenly spread on the surface of land methods is called land treatment the water of sewage percolates in the ground and the organic suspended solids remain at the surface of the ground the organic suspended solids are partly acted upon by the bacteria are partly oxidized by exposure to atmospheric action of heat light and air.