Correct Answer - Option 2 : dry weather flow
Concept:
Sewage flows within a sanitary sewer system are divided into two categories:
1. Dry weather flows.
2. Wet weather flows
Dry weather flows represents all flows within the sewer pipes on a typical day without any rainfall, which results of low flow in sewer system. During dry weather flow, insufficient flow velocities can increase the retention time within channel. Therefore, these flows could result in undesirable sedimentation of solid particles.
Wet weather flows include sewage flows and runoff that infiltrate into the sanitary sewer systems during rainfall. It also include groundwater flows that enter through defective pipe joints, connections and manhole walls.
Mixture of water and liquid waste generated due to different activities in community is called as sewage.
If sewage is generated due to domestic activities, called domestic sewage. If it is generated due to industrial activities it is called industrial sewage and if it is generated after heavy rain it is called drainage or runoff or storm sewage.
The mixture of Domestic sewage and industrial sewage is called sanitary sewage.