Which term refers to the facility where wastewater first enters a treatment plant?

The term that refers to the facility where wastewater first enters a treatment plant is "headworks." Headworks are critical components of a wastewater treatment facility, as they serve as the initial point of entry for incoming sewage and wastewater. This area typically includes screening processes to remove large solids, grit removal systems to eliminate sand and gravel, and sometimes primary flow measurement devices.

By effectively managing the first stage of treatment, headworks help to protect downstream equipment and processes from damage and inefficiency caused by larger debris or inappropriate materials. It sets the stage for subsequent treatment processes by ensuring that the water is relatively clean and only contains smaller particulates before it moves further into the treatment plant.

The other terms, while related to wastewater treatment, do not specifically refer to the initial entry point. For example, primary treatment refers to the initial removal of settleable solids from the wastewater, and a settling basin is a part of the treatment process design, where suspended solids are removed by gravity. The inlet, while it might denote the entry area, does not encompass the full range of functions performed at headworks.