Which of the following types of wastewater contains dissolved oxygen?

Domestic wastewater is the correct answer because it typically contains dissolved oxygen, which is essential for the survival of aerobic microorganisms that help in the treatment process. This type of wastewater arises from household activities such as bathing, cooking, and cleaning, all of which introduce organic matter and nutrients into the water.

The presence of dissolved oxygen is crucial in biological treatment processes, such as activated sludge systems, where microorganisms utilize oxygen to break down organic pollutants. The demand for oxygen from these microorganisms shapes the overall treatment efficiency and health of the system.

In contrast, septic wastewater generally has lower levels of dissolved oxygen due to anaerobic conditions within septic tanks, where decomposition occurs without sufficient oxygen. Industrial wastewater can vary widely depending on the type of industry and processes involved, but it can often contain pollutants that may inhibit dissolved oxygen levels. Stormwater runoff, while it can contain some oxygen, is often mixed with debris and pollutants from surfaces, leading to variable oxygen levels depending on the conditions leading up to rainfall events. Thus, domestic wastewater stands out as a type clearly characterized by its dissolved oxygen content, making it essential for effective wastewater treatment processes.