Texas Wastewater Class B Practice Exam 2026 - Free Wastewater Class B Practice Questions and Study Guide

A Rotating Biological Contactor (RBC) is indeed a fixed film biological treatment process. It consists of a series of closely spaced, parallel disks or plates mounted on a rotating shaft. As the shaft rotates, a portion of the disks is submerged in wastewater, allowing microorganisms to grow on the surface of the disks. This growth forms a biofilm, which is crucial for the biological treatment of the wastewater as the biofilm helps to break down organic matter.

In this system, the rotation of the disks exposes the biofilm to both the wastewater and atmospheric oxygen, promoting aerobic microbial activity which enhances treatment efficiency. This is a distinctive feature of fixed film systems, where the biomass is attached to a stationary surface, as opposed to being suspended in the liquid.

Other methods, like filtration systems or anaerobic digestion, do not utilize the rotating disk mechanism and are fundamentally different processes. Submerged aeration tank systems also operate differently by maintaining solids in suspension and aerating the entire volume of liquid rather than having fixed films on rotating surfaces.