Which collection system is described as carrying strictly industrial wastewater to the wastewater treatment plant, with waste varying by industry and often the most difficult to treat?

• A. Sanitary Sewer
• B. Storm
• C. Industrial
• D. Combined

Answer: (C)

The main idea is recognizing that sewer systems are categorized by what they carry. An industrial collection system is built to carry wastewater from industrial facilities. The waste from different industries can vary a lot in strength and composition, bringing in a range of contaminants that make treatment more complex. Because of this variability and potential presence of hazardous or nonbiodegradable substances, industrial wastewater is often the most difficult to treat, requiring pretreatment at the source and specialized treatment steps before reaching the wastewater treatment plant. In contrast, sanitary sewers carry domestic and some commercial wastewater, storm sewers carry rainwater and surface runoff, and combined sewers carry both wastewater and stormwater in one line.