What is it called when stormwater and domestic sewage enter the same sewer?

The situation described, where stormwater and domestic sewage flow through the same sewer system, is referred to as a combined sewer. This type of sewer system is designed to manage both rainwater runoff and wastewater from households and industries within a single pipeline.

The combined sewer system has certain implications for urban drainage and treatment processes; during periods of heavy rainfall, it can lead to sewage overflows, which may discharge untreated sewage into bodies of water. This poses potential environmental and public health risks, making the effective management and maintenance of combined sewers critical for sustainable urban infrastructure.

In contrast, a sanitary sewer exclusively carries domestic sewage, while a separate sewer is intended solely for stormwater. A storm sewer is designed specifically for the drainage of rainwater or other stormwater runoff, thus keeping it entirely distinct from sewage. Understanding these categories helps in the design and management of municipal wastewater systems to prevent contamination and ensure effective waste treatment.