California Wastewater Grade 3 Certification 2025 – 400 Free Practice Questions to Pass the Exam

The primary function of a trickling filter in wastewater treatment is to provide a surface for microbial growth. This type of treatment system consists of a bed of porous material, often stones or synthetic media, over which wastewater is distributed. As the wastewater trickles down through the media, it provides an ideal environment for the growth of biofilms, which are composed of microorganisms that break down organic matter present in the wastewater.

This microbial growth is essential because the microorganisms metabolize the organic pollutants in the water, effectively reducing the biochemical oxygen demand (BOD) and other contaminants as the water passes through the filter. The process relies heavily on the interaction between the biofilm and the wastewater, making the establishment and maintenance of a healthy microbial population critical for the trickling filter’s efficiency in treatment.

The importance of surface area for bacterial growth distinguishes this option from others, such as the separation of solids from liquids or the removal of odors, which are functions associated with different stages or components of wastewater treatment systems. The distribution of wastewater is also a relevant aspect of the trickling filter's operation, but the core purpose remains the establishment of an effective environment for microbial action.