Which of the following treatments is effective at further stabilizing oxygen-demanding substances?

The treatment that is effective at further stabilizing oxygen-demanding substances is advanced treatment. This phase goes beyond primary and secondary treatments by employing additional processes that target specific contaminants that remain after conventional treatment methods.

Advanced treatment techniques may include advanced oxidation processes, membrane filtration, reverse osmosis, or additional biological treatment stages. These methods are designed to reduce residual organic matter and other pollutants that can exert oxygen demand, thus improving the overall quality of the effluent before it is discharged into the environment or reused.

In contrast, primary treatment primarily focuses on physical separation of larger solids from wastewater through processes like sedimentation. Secondary treatment, often biological, aims at reducing organic matter and nutrients, but may not completely stabilize all oxygen-demanding substances. Tertiary treatment can provide additional purification but does not encompass the full spectrum of advanced treatment methods that target specific wastewater contaminants.