CSO Control Program --
Glossary of Terms

The following is a list of definitions of terms about combined sewers and more generally about wastewater treatment.

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Hydraulic
Pertaining to the energy, momentum, and continuity effects of liquid in motion. The term usually refers to the flow of liquids in natural environments such as rivers or manmade structures such as pipes.

Hydrograph
The variation of the flow of liquids over time.

Hydrology
The science dealing with the properties, distribution and circulation of water. The term usually refers to the flow of water on or below the land surface before reaching a stream or manmade structure.

Hydraulic Routing Model
A computer model used to simulate the flow of water in King County's pipes.

Infiltration
The penetration of water from the land surface into the soil, or the penetration of water from the soil into a sewer system by such means as defective pipes, pipe joints or connections, or manhole walls.

Inflow
Flows of extraneous water into a wastewater conveyance system from sources other than a sanitary sewer connections, such as roof leaders, basement drains, manhole covers, and cross-connections from storm sewers.

Influent
Water, wastewater or other liquid flowing into a reservoir, basin or treatment plant.

Influent pump station
A pump station that pumps flow from an interceptor sewer into a treatment plant.

Infrastructure
Streets, water, sewer lines, and other public facilities basic and necessary to the functioning of an urban area.

Interceptor sewers
The portion of a collection system that connects main and trunk sewers with the wastewater treatment plant, thereby controlling the flow into the plant.

Lag
An interval of time before additional flow enters the system.

Lateral sewers
Pipes that receive sewage from homes and businesses and transport that sewage to trunks and mains.

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