Sewer network terminology: The sewer that carries the combined discharge from an entire collecting system and conveys it to the treatment plant is called what?

Introduction / Context:
In municipal drainage and wastewater engineering, each conduit in a network has a specific function. Understanding names like house, lateral, branch, trunk, and outfall sewers is essential for planning, hydraulic design, and operations. This question checks recognition of the main carrier that finally delivers flow to the treatment plant.

Given Data / Assumptions:

• A collecting system feeds progressively larger conduits.
• Flow is ultimately conveyed to a wastewater treatment plant (WWTP).
• Standard civil engineering terminology is used.

Concept / Approach:

A house sewer connects a building to a street sewer. A lateral sewer collects several house connections along a street. A branch or sub-main receives several laterals. A trunk/main carries multiple branches. The final large conduit that conveys all collected wastewater to the WWTP or point of disposal is termed the outfall sewer.

Step-by-Step Solution:

Verification / Alternative check:

Network schematics in standard texts consistently label the terminal conveyance to the plant as the outfall sewer, distinct from in-plant influent lines or force mains associated with pumping.

Why Other Options Are Wrong:

House, lateral, and branch sewers serve upstream collection; none is the terminal carrier to the WWTP.

Common Pitfalls:

Confusing the term “outfall sewer” with “outfall” (the discharge point). The outfall sewer is the pipe; the outfall is the location.

Final Answer:

Outfall sewer