Final answer:
Aerobic secondary treatment is usually best for residential wastewater. It uses aerobic bacteria to consume organic components and is commonly used in urban areas.
Step-by-step explanation:
Aerobic secondary treatment is usually best for residential wastewater. It is a process that uses aerobic bacteria to consume the organic components of sewage.
Oxygen is critical to bacterial growth, so the sewage is often mixed with air to facilitate decomposition. This method is commonly used in urban areas for the treatment of wastewater from households and residential areas.