Final answer:
Trickling filters and Rotating Biological Contactors (RBCs) are considered fixed media systems in wastewater treatment.
Step-by-step explanation:
Trickling filters and Rotating Biological Contactors (RBCs) are considered as fixed media systems in wastewater treatment.
In a trickling filter, wastewater is sprayed or trickled over a bed of rocks, gravel, or synthetic materials where a biofilm of microorganisms grows. These microorganisms break down the organic matter in the wastewater.
Similarly, RBCs are tanks filled with plastic media that rotate and are partially submerged in the wastewater. The microorganisms attached to the media degrade the pollutants in the water.