Correct Answer - Option 1 : Sewage and rain water
Concept:
Sewerage system:
The entire system developed for the collection, treating, and disposing of the sewage safely is called the sewerage system. Modern sewerage systems fall under mainly three categories-
1). Combined sewerage system:
A combined sewer system is a sewer that accepts stormwater, sanitary water(sewage), then the sewage is treated in the sewerage treatment plant. This system is mainly used in towns where streets are narrow and rainfall is less than moderate.
2). Separate sewerage system:
In this system, the sanitary sewage and stormwater are carried separately in two sets of sewers. The sewage is conveyed to the wastewater treatment plant and the stormwater is discharged into rivers without treatment.
3). Partially Separate sewerage system:
A partially separate system is a combination of a combined sewerage system and separate sewerage systems. This type of sewerage system helps decrease the load from a combined sewerage system because only the water from initial rainfalls (water from acid rain) is added to sewage water and after that this system work as a separate system.
