- Trickling Filter A secondary wastewater treatment process where wastewater is distributed over a bed of filter media, allowing biological organisms to break down organic matter. - Treatment Sequence In a typical wastewater treatment plant, the sequence of operations involving trickling filters is: Screening -> Primary Sedimentation Tank -> Trickling Filter -> Final Settling Tank. - Purpose Trickling filters are used to remove dissolved and suspended organic solids from wastewater. The organic solids produced during filtration are removed in the subsequent final settling tank.