Wastewater Collection System Components

Contributed by Phil Vela

A wastewater collection system is a series of pipes, tunnels, conduits and other devices that transport wastewater from homes, businesses and industries to a central treatment plant. Transport of the wastewater is either by gravity (the preferred method) or with the use sanitary lift or pump stations to either a location that gravity can be used or to another lift or pump station and finally to the wastewater treatment plant. In either case, the collection system has many functioning parts as shown and described below.

Figure 1 (source) shows the different types and sizes of sewer lines in a typical wastewater collection system. They range from the smallest (approximately 4 inches) located at the home or business to the large truck mains (minimum 12 inches and can be as large as 27 ft tunnels in large cities) that carry the sewerage to the waste treatment plant. A brief description of each follows.

Here's house the Louisville Metropolitan Sewer District describes each of the components:

House Sewer conveys the sewerage from a building to the lateral or branch lines.

Lateral & Branch Sewers are the upper ends of the municipal sewer system. Laterals dead-end at their upstream end with branch sewers collecting the wastewater from several lateral sewer lines.

Sub-main Sewers are collectors for numerous lateral and branch sewers from an area of several hundred acres or a specific neighborhood or housing development They convey the wastewater to larger trunk sewer lines, to lift stations or to a neighborhood package water quality treatment center.

Trunk/Main Sewers serve as the main arteries of the wastewater collection system. They collect and convey the wastewater from numerous main sewer lines either to a water quality treatment center or to a interceptor sewer.

Interceptor Sewers receive the wastewater numerous from trunk sewers and convey it to a water quality treatment center. These are the largest diameter lines in the sewer system and the furthest downstream in the system.

Lift or Pump Stations are utilized in gravity sewer systems to lift (pump) wastewater to a higher elevation when the route followed by a gravity sewer would require the sewer to be laid at an insufficient slope or at an impractical depth. Lift stations vary in size and type depending upon the quantity of wastewater to be handled and the height it must be lifted.

This video from American Water College describes the components of a wastewater collection system: