The Trickling Filter at a Sewage Treatment Plant Works by

The trickling filter at a sewage treatment plant works by

A) passing wastewater through fine sand, mechanically removing fine pollution particles.
B) passing wastewater through a thick bed of rocks that contain chemicals that sterilize the water and neutralize chemical pollutants or bind with them to produce a harmless precipitate.
C) passing wastewater through a thick bed of rocks. Biofilms of bacteria and fungi on the rocks remove much of the organic material dissolved in the wastewater.
D) adding fertilizer to wastewater and passing it through a culture medium rich in oil-eating prokaryotes.