Final answer:
A restaurant's storm sewer system typically disposes of rainwater and may also include gray water if the sewer system is combined. These combined systems can lead to pollution during heavy rainfall as they may overflow. Wastewater treatment plants are key to processing and possibly reusing treated water.
Step-by-step explanation:
A restaurant's storm sewer system disposes of rainwater and sometimes gray water. Rainwater is explicitly collected from surfaces during rainfall events, whereas gray water is water from domestic activities such as laundry, dishwashing, and bathing, but not from toilets. However, in some combined sewer systems, which are less common today, the sewers carry both sewage (including human waste) and stormwater runoff. This can lead to pollution during heavy rainfall if the system overflows. In short, the answer to the student's question would be d. a and c, assuming the restaurant is part of a combined sewer system.
Wastewater treatment plants play a critical role in processing wastewater, which includes sewage and water used in various industrial processes. The treated wastewater can sometimes be reused for irrigation and landscaping. Unfortunately, during heavy rainfalls, stormwater can exceed sewer capacity in combined sewer systems, resulting in discharge of untreated sewage directly into water bodies. Improving these systems and separating stormwater from sewage can mitigate such pollution.