noun
treated water; treated wastewater; treated sewage
Refers to water that has undergone treatment to remove contaminants, commonly used in discussions of wastewater management and environmental discharge.
処理水を川に放流する前に、水質を検査します。
Before releasing treated water into the river, we test its quality.
この工場では、処理水の一部を冷却用に再利
This factory reuses some of the treated water for cooling.
下水 is raw sewage or wastewater, whereas 処理水 is the treated product.
Compound of 処理 (treatment) and 水 (water). A modern technical term with no special historical derivation.