How does infiltration and inflow (I/I) affect a collection system?

Infiltration and inflow (I/I) refer to the unwanted flow of water into a sewer system, either through the groundwater seeping into the pipes (infiltration) or through direct connections from stormwater or surface runoff (inflow). When there is significant I/I, it increases the volume of wastewater that the system must transport.

This excess water can easily overwhelm the capacity of the collection system, which is typically designed to handle a specific volume of sewage. When the system is overwhelmed, it can lead to combined sewer overflows (CSOs) or sanitary sewer overflows (SSOs). Such overflows pose serious environmental and public health risks as untreated wastewater may be discharged into local waterways or back up into homes and businesses.

Therefore, the correct answer highlights a critical challenge faced by collection systems managing I/I, demonstrating that it can lead to significant operational issues if not properly managed.