What is defined as a single system used for the treatment of domestic wastewater?

The correct answer describes a single system of treatment tanks that operates specifically for a single building, which aligns with the definition of domestic wastewater treatment systems. This setup typically includes components like septic tanks or small-scale aerobic treatment units that are tailored to handle the wastewater generated by a residential facility. By concentrating the treatment process within one location, it ensures that the systems are manageable, efficient, and designed to meet the specific needs of the household.

In contrast, the other options involve broader systems or collaborative efforts that do not specifically focus on the treatment of domestic wastewater from a single building. For example, a system with multiple treatment facilities serving a community is indicative of a larger-scale infrastructure, which may not be considered a single system by definition. Additionally, a complex network of treatment plants for industrial waste focuses on different treatment requirements and regulations, while a collaborative treatment system for residential areas suggests a more communal approach that doesn't limit itself to the single-unit treatment concept.