Sewer Bypass Report Terms and Definitions

Plant Bypass

Describes a situation where wastewater has been diverted around one or more unit processes within the plant, with the diverted flow being returned to the plant treatment train upstream of the final effluent sampling location in order to discharge to the environment through the outfall. The flow is being treated by the other treatment trains being accessed.

Plant Overflow 

Describes a discharge to the environment from the plant at a location other than the plant outfall, or into the plant outfall downstream of the final effluent sampling location. This flow is usually not treated except for disinfection.

Collection System Overflow

Describes a discharge from a point in the collection system (like a lift station or manhole) that does not undergo any treatment, or only receives partial treatment before being discharged to the environment.

Plant By-Pass: Flow exceeds design capacity

Describes an event when flows into the plant exceed the design peak flow capacity of the plant, even if the flow is being treated through all available treatment trains.

Event

Means an action or occurrence, at a given location that causes a bypass or overflow. An event ends when there is no recurrence in the 12 hours following the end of the last bypass or overflow. Two “events” are separated by at least 12 hours during which there has been no recurrence.