What is sewage? Through what is sewage water passed before being disposed of?

(N/A) Large quantities of wastewater are generated every day in cities and towns. $A$ major component of this wastewater is human excreta. This municipal wastewater is called sewage.
It contains a large amount of organic matter and microbes,many of which are pathogenic.
This urban wastewater cannot be discharged directly into natural water bodies like rivers and streams.
Sewage is treated in sewage treatment plants $(STPs)$ to make it less polluting.
The treatment of wastewater is carried out by heterotrophic microbes that are naturally present in the sewage.