What is the primary purpose of a septic tank in an OSWW system?

The primary purpose of a septic tank in an Onsite Wastewater Systems (OSWW) setup is the initial treatment of wastewater. During this process, wastewater enters the septic tank, where it undergoes several key steps. The tank allows solids to settle at the bottom, forming sludge, while lighter materials, such as oils and grease, float to the top, forming scum. The clarified liquid that remains in the middle is referred to as effluent.

This process is crucial because it enables the effective separation and initial breakdown of solids and pathogens present in the wastewater. By treating the wastewater before it moves into the drain field or another treatment area, the septic tank plays a vital role in protecting public health and the environment from the potential hazards posed by untreated waste. The other options note functions related to the septic system but do not define the primary role of the septic tank in the treatment process. For instance, while a septic tank does hold solid waste temporarily, that is not its primary purpose, which is focused on the treatment aspect.