Sewage treatment is the process of removing contaminants from sewage before it affects aquifers or natural water bodies including rivers, lakes, estuaries, and seas.
There are three levels of sewage water treatment: primary, secondary, and tertiary.
Primary sewage water treatment entails filtration and sedimentation of solid waste inside the water.
Secondary sewage water treatment includes biofiltration, oxidation, and aeration.
Tertiary sewage water treatment involves the removal of inorganic chemicals such as nitrogen and phosphorus.
Primary treatment of sewage involves:
The initial step of sewage treatment is the primary treatment, in which wastewater is dumped in a holding tank and solids sink to the bottom where they are collected, while lighter substances such as fats and oils are scraped off the top.
Primary treatment involves storing sewage in a basin where solids (sludge) fall to the bottom and oil and lighter substances float to the top.
After removing these layers, the residual liquid can be transferred to secondary treatment.
Sludge digestion is a different procedure for treating sewage sludge.