sewage treatment plant
A facility where sewage is treated and purified before being released into the environment.
The sewage treatment plant in this town has introduced the latest equipment.
下水処理場 is a more common term for a sewage treatment plant. 終末処理場 is a technical term often used in official or engineering contexts.
Compound of 終末 (end, final) + 処理 (treatment) + 場 (place). The term refers to the final stage of sewage treatment.